![xiv Guided tour
DESIGN PROCESS
In this part, we concentrate on how design practice
addresses the critical feature of an interactive system –
usability from the human perspective. The chapters in
this part promote the purposeful design of more usable
interactive systems. We begin in Chapter 5 by introducing
the key elements in the interaction design process. These
elements are then expanded in later chapters.
Chapter 6 discusses the design process in more detail,
specifically focussing on the place of user-centered design
within a software engineering framework. Chapter 7 high-
lights the range of design rules that can help us to specify
usable interactive systems, including abstract principles,
guidelines and other design representations.
In Chapter 8, we provide an overview of implementa-
tion support for the programmer of an interactive system.
Chapter 9 is concerned with the techniques used to evalu-
ate the interactive system to see if it satisfies user needs.
Chapter 10 discusses how to design a system to be univer-
sally accessible, regardless of age, gender, cultural background
or ability. In Chapter 11 we discuss the provision of user
support in the form of help systems and documentation.
P A R T
2 MODELING RICH
INTERACTION
OVERVIEW
We operate within an ecology of people, physical artifacts
and electronic systems, and this rich ecology has recently
become more complex as electronic devices invade the
workplace and our day-to-day lives. We need methods
to deal with these rich interactions.
n Status–event analysis is a semi-formal, easy to apply
technique that:
– classifies phenomena as event or status
– embodies naïve psychology
– highlights feedback problems in interfaces.
n Aspects of rich environments can be incorporated into
methods such as task analysis:
– other people
– information requirements
– triggers for tasks
– modeling artifacts
– placeholders in task sequences.
n New sensor-based systems do not require explicit
interaction; this means:
– new cognitive and interaction models
– new design methods
– new system architectures.
18
19.3 Computer-mediated communication 675
CuSeeMe
Special-purpose video conferencing is still relatively expensive, but low-fidelity desktop
video conferencing is now within the reach of many users of desktop computers. Digital video
cameras are now inexpensive and easily obtainable. They often come with pre-packaged video
phone or video conferencing software. However, the system which has really popularized
video conferencing is a web-based tool. CuSeeMe works over the internet allowing participants
across the world owning only a basic digital video camera to see and talk to one another. The soft-
ware is usually public domain (although there are commercial versions) and the services allowing
connection are often free. The limited bandwidth available over long-distance internet links means
that video quality and frame rates are low and periodic image break-up may occur. In fact, it is
sound break-up which is more problematic. After all, we can talk to one another quite easily with-
out seeing one another, but find it very difficult over a noisy phone line. Often participants may
see one another’s video image, but actually discuss using a synchronous text-based ‘talk’ program.
CuSeeMe – video conferencing on the internet. Source: Courtesy of Geoff Ellis
440 Chapter 12 n Cognitive models
Worked exercise Do a keystroke-level analysis for opening up an application in a visual desktop interface using
a mouse as the pointing device, comparing at least two different methods for performing the
task. Repeat the exercise using a trackball. Consider how the analysis would differ for various
positions of the trackball relative to the keyboard and for other pointing devices.
Answer We provide a keystroke-level analysis for three different methods for launching an
application on a visual desktop. These methods are analyzed for a conventional one-
button mouse, a trackball mounted away from the keyboard and one mounted close to
the keyboard. The main distinction between the two trackballs is that the second one
does not require an explicit repositioning of the hands, that is there is no time required
for homing the hands between the pointing device and the keyboard.
Method 1 Double clicking on application icon
Steps Operator Mouse Trackball1 Trackball2
1. Move hand to mouse H[mouse] 0.400 0.400 0.000
2. Mouse to icon P[to icon] 0.664 1.113 1.113
3. Double click 2B[click] 0.400 0.400 0.400
4. Return to keyboard H[kbd] 0.400 0.400 0.000
Total times 1.864 2.313 1.513
Method 2 Using an accelerator key
Steps Operator Mouse Trackball1 Trackball2
1. Move hand to mouse H[mouse] 0.400 0.400 0.000
2. Mouse to icon P[to icon] 0.664 1.113 1.113
3. Click to select B[click] 0.200 0.200 0.200
4. Pause M 1.350 1.350 1.350
5. Return to keyboard H[kbd] 0.400 0.400 0.000
6. Press accelerator K 0.200 0.200 0.200
Total times 3.214 3.663 2.763
Method 3 Using a menu
Steps Operator Mouse Trackball1 Trackball2
1. Move hand to mouse H[mouse] 0.400 0.400 0.000
2. Mouse to icon P[to icon] 0.664 1.113 1.113
3. Click to select B[click] 0.200 0.200 0.200
4. Pause M 1.350 1.350 1.350
5. Mouse to file menu P 0.664 1.113 1.113
6. Pop-up menu B[down] 0.100 0.100 0.100
7. Drag to open P[drag] 0.713 1.248 1.248
8. Release mouse B[up] 0.100 0.100 0.100
9. Return to keyboard H[kbd] 0.400 0.400 0.000
Total times 4.591 6.024 5.224
The part structure separates out introductory and more
advanced material, with each part opener giving a simple
description of what its constituent chapters cover
Bullet points at the start of each chapter highlight the
core coverage
Worked exercises within chapters provide step-by-step
guidelines to demonstrate problem-solving techniques
Boxed asides contain descriptions of particular tasks or
technologies for additional interest, experimentation
and discussion](https://image.slidesharecdn.com/1172759-250607150208-e7d1590c/85/Humancomputer-Interaction-3rd-Edition-Alan-Dix-19-320.jpg)
![HCI in the curriculum 7
were used primarily by expert specialists, concentration on the interface was a lux-
ury that was often relinquished. Now designers cannot afford to ignore the interface
in favour of the functionality of their systems: the two are too closely intertwined. If
the interface is poor, the functionality is obscured; if it is well designed, it will allow
the system’s functionality to support the user’s task.
Increasingly, therefore, computer science educators cannot afford to ignore HCI.
We would go as far as to claim that HCI should be integrated into every computer
science or software engineering course, either as a recurring feature of other modules
or, preferably, as a module itself. It should not be viewed as an ‘optional extra’
(although, of course, more advanced HCI options can complement a basic core
course). This view is shared by the ACM SIGCHI curriculum development group,
who propose a curriculum for such a core course [9]. The topics included in this
book, although developed without reference to this curriculum, cover the main
emphases of it, and include enough detail and coverage to support specialized
options as well.
In courses other than computer science, HCI may well be an option specializing
in a particular area, such as cognitive modeling or task analysis. Selected use of the
relevant chapters of this book can also support such a course.
HCI must be taken seriously by designers and educators if the requirement for
additional complexity in the system is to be matched by increased clarity and usabil-
ity in the interface. In this book we demonstrate how this can be done in practice.
DESIGN FOCUS
Quick fixes
You should expect to spend both time and money on interface design, just as you would with other
parts of a system. So in one sense there are no quick fixes. However, a few simple steps can make a
dramatic improvement.
Think ‘user’
Probably 90% of the value of any interface design technique is that it forces the designer to remember
that someone (and in particular someone else) will use the system under construction.
Try it out
Of course, many designers will build a system that they find easy and pleasant to use, and they find
it incomprehensible that anyone else could have trouble with it. Simply sitting someone down with
an early version of an interface (without the designer prompting them at each step!) is enormously
valuable. Professional usability laboratories will have video equipment, one-way mirrors and other
sophisticated monitors, but a notebook and pencil and a home-video camera will suffice (more about
evaluation in Chapter 9).
Involve the users
Where possible, the eventual users should be involved in the design process. They have vital know-
ledge and will soon find flaws. A mechanical syringe was once being developed and a prototype was
demonstrated to hospital staff. Happily they quickly noticed the potentially fatal flaw in its interface.](https://image.slidesharecdn.com/1172759-250607150208-e7d1590c/85/Humancomputer-Interaction-3rd-Edition-Alan-Dix-38-320.jpg)
![12 Chapter 1 n The human
INTRODUCTION
This chapter is the first of four in which we introduce some of the ‘foundations’ of
HCI. We start with the human, the central character in any discussion of interactive
systems. The human, the user, is, after all, the one whom computer systems are de-
signed to assist. The requirements of the user should therefore be our first priority.
In this chapter we will look at areas of human psychology coming under the general
banner of cognitive psychology. This may seem a far cry from designing and building
interactive computer systems, but it is not. In order to design something for some-
one, we need to understand their capabilities and limitations. We need to know if
there are things that they will find difficult or, even, impossible. It will also help us to
know what people find easy and how we can help them by encouraging these things.
We will look at aspects of cognitive psychology which have a bearing on the use of com-
puter systems: how humans perceive the world around them, how they store and
process information and solve problems, and how they physically manipulate objects.
We have already said that we will restrict our study to those things that are relev-
ant to HCI. One way to structure this discussion is to think of the user in a way that
highlights these aspects. In other words, to think of a simplified model of what is
actually going on. Many models have been proposed and it useful to consider one of
the most influential in passing, to understand the context of the discussion that is to
follow. In 1983, Card, Moran and Newell [56] described the Model Human Processor,
which is a simplified view of the human processing involved in interacting with
computer systems. The model comprises three subsystems: the perceptual system,
handling sensory stimulus from the outside world, the motor system, which controls
actions, and the cognitive system, which provides the processing needed to connect
the two. Each of these subsystems has its own processor and memory, although
obviously the complexity of these varies depending on the complexity of the tasks
the subsystem has to perform. The model also includes a number of principles of
operation which dictate the behavior of the systems under certain conditions.
We will use the analogy of the user as an information processing system, but in
our model make the analogy closer to that of a conventional computer system.
Information comes in, is stored and processed, and information is passed out. We
will therefore discuss three components of this system: input–output, memory and
processing. In the human, we are dealing with an intelligent information-processing
system, and processing therefore includes problem solving, learning, and, con-
sequently, making mistakes. This model is obviously a simplification of the real
situation, since memory and processing are required at all levels, as we have seen in
the Model Human Processor. However, it is convenient as a way of grasping how
information is handled by the human system. The human, unlike the computer, is
also influenced by external factors such as the social and organizational environ-
ment, and we need to be aware of these influences as well. We will ignore such
factors for now and concentrate on the human’s information processing capabilities
only. We will return to social and organizational influences in Chapter 3 and, in
more detail, in Chapter 13.
1.1](https://image.slidesharecdn.com/1172759-250607150208-e7d1590c/85/Humancomputer-Interaction-3rd-Edition-Alan-Dix-43-320.jpg)
![22 Chapter 1 n The human
Reading
So far we have concentrated on the perception of images in general. However,
the perception and processing of text is a special case that is important to interface
design, which invariably requires some textual display. We will therefore end
this section by looking at reading. There are several stages in the reading process.
First, the visual pattern of the word on the page is perceived. It is then decoded
with reference to an internal representation of language. The final stages of lan-
guage processing include syntactic and semantic analysis and operate on phrases or
sentences.
We are most concerned with the first two stages of this process and how they
influence interface design. During reading, the eye makes jerky movements called
saccades followed by fixations. Perception occurs during the fixation periods, which
account for approximately 94% of the time elapsed. The eye moves backwards over
the text as well as forwards, in what are known as regressions. If the text is complex
there will be more regressions.
Adults read approximately 250 words a minute. It is unlikely that words are
scanned serially, character by character, since experiments have shown that words can
be recognized as quickly as single characters. Instead, familiar words are recognized
using word shape. This means that removing the word shape clues (for example, by
capitalizing words) is detrimental to reading speed and accuracy.
The speed at which text can be read is a measure of its legibility. Experiments have
shown that standard font sizes of 9 to 12 points are equally legible, given pro-
portional spacing between lines [346]. Similarly line lengths of between 2.3 and 5.2
inches (58 and 132 mm) are equally legible. However, there is evidence that reading
from a computer screen is slower than from a book [244]. This is thought to be
due to a number of factors including a longer line length, fewer words to a page,
DESIGN FOCUS
Where’s the middle?
Optical illusions highlight the differences between the way things are and the way we perceive them –
and in interface design we need to be aware that we will not always perceive things exactly as they are.
The way that objects are composed together will affect the way we perceive them, and we do not per-
ceive geometric shapes exactly as they are drawn. For example, we tend to magnify horizontal lines and
reduce vertical. So a square needs to be slightly increased in height to appear square and lines will
appear thicker if horizontal rather than vertical.
Optical illusions also affect page symmetry. We tend to see the center of a page as being a little above
the actual center – so if a page is arranged symmetrically around the actual center, we will see it as too
low down. In graphic design this is known as the optical center – and bottom page margins tend to be
increased by 50% to compensate.](https://image.slidesharecdn.com/1172759-250607150208-e7d1590c/85/Humancomputer-Interaction-3rd-Edition-Alan-Dix-53-320.jpg)
![1.2 Input–output channels 23
orientation and the familiarity of the medium of the page. These factors can of
course be reduced by careful design of textual interfaces.
A final word about the use of contrast in visual display: a negative contrast (dark
characters on a light screen) provides higher luminance and, therefore, increased
acuity, than a positive contrast. This will in turn increase legibility. However, it will
also be more prone to flicker. Experimental evidence suggests that in practice negat-
ive contrast displays are preferred and result in more accurate performance [30].
1.2.2 Hearing
The sense of hearing is often considered secondary to sight, but we tend to under-
estimate the amount of information that we receive through our ears. Close your eyes
for a moment and listen. What sounds can you hear? Where are they coming from?
What is making them? As I sit at my desk I can hear cars passing on the road outside,
machinery working on a site nearby, the drone of a plane overhead and bird song.
But I can also tell where the sounds are coming from, and estimate how far away they
are. So from the sounds I hear I can tell that a car is passing on a particular road near
my house, and which direction it is traveling in. I know that building work is in
progress in a particular location, and that a certain type of bird is perched in the tree
in my garden.
The auditory system can convey a lot of information about our environment. But
how does it work?
The human ear
Just as vision begins with light, hearing begins with vibrations in the air or sound
waves. The ear receives these vibrations and transmits them, through various stages,
to the auditory nerves. The ear comprises three sections, commonly known as the
outer ear, middle ear and inner ear.
The outer ear is the visible part of the ear. It has two parts: the pinna, which is
the structure that is attached to the sides of the head, and the auditory canal, along
which sound waves are passed to the middle ear. The outer ear serves two purposes.
First, it protects the sensitive middle ear from damage. The auditory canal contains
wax which prevents dust, dirt and over-inquisitive insects reaching the middle ear.
It also maintains the middle ear at a constant temperature. Secondly, the pinna and
auditory canal serve to amplify some sounds.
The middle ear is a small cavity connected to the outer ear by the tympanic
membrane, or ear drum, and to the inner ear by the cochlea. Within the cavity are the
ossicles, the smallest bones in the body. Sound waves pass along the auditory canal
and vibrate the ear drum which in turn vibrates the ossicles, which transmit the
vibrations to the cochlea, and so into the inner ear. This ‘relay’ is required because,
unlike the air-filled outer and middle ears, the inner ear is filled with a denser
cochlean liquid. If passed directly from the air to the liquid, the transmission of the
sound waves would be poor. By transmitting them via the ossicles the sound waves
are concentrated and amplified.](https://image.slidesharecdn.com/1172759-250607150208-e7d1590c/85/Humancomputer-Interaction-3rd-Edition-Alan-Dix-54-320.jpg)
Humancomputer Interaction 3rd Edition Alan Dix
- 1. Humancomputer Interaction 3rd Edition Alan Dix download https://ebookbell.com/product/humancomputer-interaction-3rd- edition-alan-dix-2345518 Explore and download more ebooks at ebookbell.com
- 2. Here are some recommended products that we believe you will be interested in. You can click the link to download. Humancomputer Interaction Thematic Area Hci 2022 Held As Part Of The 24th Hci International Conference Hcii 2022 Virtual Event June 26 July 1 2022 Proceedings Part I Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2022-held-as-part-of-the-24th-hci-international-conference- hcii-2022-virtual-event-june-26-july-1-2022-proceedings-part-i- masaaki-kurosu-47226914 Humancomputer Interaction Technological Innovation Thematic Area Hci 2022 Held As Part Of The 24th Hci International Conference Hcii 2022 Virtual Event June 26 July 1 2022 Proceedings Part Ii Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-technological- innovation-thematic-area-hci-2022-held-as-part-of-the-24th-hci- international-conference-hcii-2022-virtual-event- june-26-july-1-2022-proceedings-part-ii-masaaki-kurosu-47238032 Humancomputer Interaction 8th Iberoamerican Workshop Hcicollab 2022 Havana Cuba October 1315 2022 Revised Selected Papers Vanessa Agredodelgado https://ebookbell.com/product/humancomputer-interaction-8th- iberoamerican-workshop-hcicollab-2022-havana-cuba- october-1315-2022-revised-selected-papers-vanessa- agredodelgado-49028530 Humancomputer Interaction Thematic Area Hci 2023 Held As Part Of The 25th Hci International Conference Hcii 2023 Copenhagen Denmark July 2328 2023 Proceedings Part Iv Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2023-held-as-part-of-the-25th-hci-international-conference- hcii-2023-copenhagen-denmark-july-2328-2023-proceedings-part-iv- masaaki-kurosu-50818530
- 3. Humancomputer Interaction Thematic Area Hci 2023 Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2023-masaaki-kurosu-50883694 Human Computer Interaction Using Hand Gestures Prashan Premaratne https://ebookbell.com/product/human-computer-interaction-using-hand- gestures-prashan-premaratne-57204874 Humancomputer Interaction Thematic Area Hci 2024 Held As Part Of The 26th Hci International Conference Hcii 2024 Washington Dc Usa June 29 July 4 2024 Proceedings Part V 2024th Edition Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2024-held-as-part-of-the-26th-hci-international-conference- hcii-2024-washington-dc-usa-june-29-july-4-2024-proceedings- part-v-2024th-edition-masaaki-kurosu-58592758 Humancomputer Interaction Thematic Area Hci 2024 Held As Part Of The 26th Hci International Conference Hcii 2024 Washington Dc Usa June 29 July 4 2024 Proceedings Part I 2024th Edition Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2024-held-as-part-of-the-26th-hci-international-conference- hcii-2024-washington-dc-usa-june-29-july-4-2024-proceedings- part-i-2024th-edition-masaaki-kurosu-58663384 Humancomputer Interaction Thematic Area Hci 2024 Proceedings Part Iii 2024th Edition Masaaki Kurosu https://ebookbell.com/product/humancomputer-interaction-thematic-area- hci-2024-proceedings-part-iii-2024th-edition-masaaki-kurosu-58686938
- 4. Humancomputer Interaction Interact 2009 12th Ifip Tc 13 International Conference Uppsala Sweden August 2428 2009 Proceedings Part Ii 1st Edition Julio Mirborrs https://ebookbell.com/product/humancomputer-interaction- interact-2009-12th-ifip-tc-13-international-conference-uppsala-sweden- august-2428-2009-proceedings-part-ii-1st-edition-julio- mirborrs-2023284
- 5. ALAN DIX, JANET FINLAY, GREGORY D. ABOWD, RUSSELL BEALE THIRD EDITION THIRD EDITION HUMAN–COMPUTER INTERACTION Much has changed since the first edition of Human–Computer Interaction was published. Ubiquitous computing and rich sensor-filled environments are finding their way out of the laboratory, not just into movies but also into our workplaces and homes. The computer has broken out of its plastic and glass bounds providing us with networked societies where personal computing devices from mobile phones to smart cards fill our pockets and electronic devices surround us at home and work. The web too has grown from a largely academic network into the hub of business and everyday lives. As the distinctions between the physical and the digital, and between work and leisure start to break down, human–computer interaction is also changing radically. The excitement of these changes is captured in this new edition, which also looks forward to other emerging technologies. However, the book is firmly rooted in strong principles and models independent of the passing technologies of the day: these foundations will be the means by which today’s students will understand tomorrow’s technology. The third edition of Human–Computer Interaction can be used for introductory and advanced courses on HCI, Interaction Design, Usability or Interactive Systems Design. It will also prove an invaluable reference for professionals wishing to design usable computing devices. Accompanying the text is a comprehensive website containing a broad range of material for instructors, students and practitioners, a full text search facility for the book, links to many sites of additional interest and much more: go to www.hcibook.com Alan Dix is Professor in the Department of Computing, Lancaster, UK. Janet Finlay is Professor in the School of Computing, Leeds Metropolitan University, UK. Gregory D. Abowd is Associate Professor in the College of Computing and GVU Center at Georgia Tech, USA. Russell Beale is lecturer at the School of Computer Science, University of Birmingham, UK. Cover illustration by Peter Gudynas New to this edition: � A revised structure, reflecting the growth of HCI as a discipline, separates out basic material suitable for introductory courses from more detailed models and theories. � New chapter on interaction design adds material on scenarios and basic navigation design. � New chapter on universal design, substantially extending the coverage of this material in the book. � Updated and extended treatment of socio/contextual issues. � Extended and new material on novel interaction, including updated ubicomp material, designing experience, physical sensors and a new chapter on rich interaction. � Updated material about the web including dynamic content. � Relaunched website including case studies, WAP access and search. www.pearson-books.com HUMAN–COMPUTER INTERACTION DIX FINLAY ABOWD BEALE
- 7. We work with leading authors to develop the strongest educational materials in computing, bringing cutting-edge thinking and best learning practice to a global market. Under a range of well-known imprints, including Prentice Hall, we craft high quality print and electronic publications which help readers to understand and apply their content, whether studying or at work. To find out more about the complete range of our publishing, please visit us on the world wide web at: www.pearsoned.co.uk
- 8. Human–Computer Interaction Third Edition Alan Dix, Lancaster University Janet Finlay, Leeds Metropolitan University Gregory D. Abowd, Georgia Institute of Technology Russell Beale, University of Birmingham
- 9. Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the world wide web at: www.pearsoned.co.uk First published 1993 Second edition published 1998 Third edition published 2004 © Prentice-Hall Europe 1993, 1998 © Pearson Education Limited 2004 The rights of Alan Dix, Janet E. Finlay, Gregory D. Abowd and Russell Beale to be identified as authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP. All trademarks used herein are the property of their respective owners. The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners. ISBN-13: 978-0-13-046109-4 ISBN-10: 0-13-046109-1 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library 10 9 8 7 6 5 4 3 10 09 08 07 06 Typeset in 10/121 /2pt Minion by 35 Printed and bound by Scotprint, Haddington
- 10. BRIEF CONTENTS Guided tour xiv Foreword xvi Preface to the third edition xix Publisher’s acknowledgements xxiii Introduction 1 FOUNDATIONS 9 Chapter 1 The human 11 Chapter 2 The computer 59 Chapter 3 The interaction 123 Chapter 4 Paradigms 164 DESIGN PROCESS 189 Chapter 5 Interaction design basics 191 Chapter 6 HCI in the software process 225 Chapter 7 Design rules 258 Chapter 8 Implementation support 289 Chapter 9 Evaluation techniques 318 Chapter 10 Universal design 365 Chapter 11 User support 395 MODELS AND THEORIES 417 Chapter 12 Cognitive models 419 Chapter 13 Socio-organizational issues and stakeholder requirements 450 Part 3 Part 2 Part 1
- 11. vi Brief Contents Chapter 14 Communication and collaboratio0n models 475 Chapter 15 Task analysis 510 Chapter 16 Dialog notations and design 544 Chapter 17 Models of the system 594 Chapter 18 Modeling rich interaction 629 OUTSIDE THE BOX 661 Chapter 19 Groupware 663 Chapter 20 Ubiquitous computing and augmented realities 716 Chapter 21 Hypertext, multimedia and the world wide web 748 References 791 Index 817 Part 4
- 12. CONTENTS Guided tour xiv Foreword xvi Preface to the third edition xix Publisher’s acknowledgements xxiii Introduction 1 FOUNDATIONS 9 Chapter 1 The human 11 1.1 Introduction 12 1.2 Input–output channels 13 Design Focus: Getting noticed 16 Design Focus: Where’s the middle? 22 1.3 Human memory 27 Design Focus: Cashing in 30 Design Focus: 7 ± 2 revisited 32 1.4 Thinking: reasoning and problem solving 39 Design Focus: Human error and false memories 49 1.5 Emotion 51 1.6 Individual differences 52 1.7 Psychology and the design of interactive systems 53 1.8 Summary 55 Exercises 56 Recommended reading 57 Chapter 2 The computer 59 2.1 Introduction 60 2.2 Text entry devices 63 Design Focus: Numeric keypads 67 2.3 Positioning, pointing and drawing 71 Part 1
- 13. viii Contents 2.4 Display devices 78 Design Focus: Hermes: a situated display 86 2.5 Devices for virtual reality and 3D interaction 87 2.6 Physical controls, sensors and special devices 91 Design Focus: Feeling the road 94 Design Focus: Smart-Its – making using sensors easy 96 2.7 Paper: printing and scanning 97 Design Focus: Readability of text 101 2.8 Memory 107 2.9 Processing and networks 114 Design Focus: The myth of the infinitely fast machine 116 2.10 Summary 120 Exercises 121 Recommended reading 122 Chapter 3 The interaction 123 3.1 Introduction 124 3.2 Models of interaction 124 Design Focus: Video recorder 130 3.3 Frameworks and HCI 130 3.4 Ergonomics 131 Design Focus: Industrial interfaces 133 3.5 Interaction styles 136 Design Focus: Navigation in 3D and 2D 144 3.6 Elements of the WIMP interface 145 Design Focus: Learning toolbars 151 3.7 Interactivity 152 3.8 The context of the interaction 154 Design Focus: Half the picture? 155 3.9 Experience, engagement and fun 156 3.10 Summary 160 Exercises 161 Recommended reading 162 Chapter 4 Paradigms 164 4.1 Introduction 165 4.2 Paradigms for interaction 165 4.3 Summary 185 Exercises 186 Recommended reading 187
- 14. Contents ix DESIGN PROCESS 189 Chapter 5 Interaction design basics 191 5.1 Introduction 192 5.2 What is design? 193 5.3 The process of design 195 5.4 User focus 197 Design Focus: Cultural probes 200 5.5 Scenarios 201 5.6 Navigation design 203 Design Focus: Beware the big button trap 206 Design Focus: Modes 207 5.7 Screen design and layout 211 Design Focus: Alignment and layout matter 214 Design Focus: Checking screen colors 219 5.8 Iteration and prototyping 220 5.9 Summary 222 Exercises 223 Recommended reading 224 Chapter 6 HCI in the software process 225 6.1 Introduction 226 6.2 The software life cycle 226 6.3 Usability engineering 237 6.4 Iterative design and prototyping 241 Design Focus: Prototyping in practice 245 6.5 Design rationale 248 6.6 Summary 256 Exercises 257 Recommended reading 257 Chapter 7 Design rules 258 7.1 Introduction 259 7.2 Principles to support usability 260 7.3 Standards 275 7.4 Guidelines 277 7.5 Golden rules and heuristics 282 7.6 HCI patterns 284 7.7 Summary 286 Exercises 287 Recommended reading 288 Part 2
- 15. x Contents Chapter 8 Implementation support 289 8.1 Introduction 290 8.2 Elements of windowing systems 291 8.3 Programming the application 296 Design Focus: Going with the grain 301 8.4 Using toolkits 302 Design Focus: Java and AWT 304 8.5 User interface management systems 306 8.6 Summary 313 Exercises 314 Recommended reading 316 Chapter 9 Evaluation techniques 318 9.1 What is evaluation? 319 9.2 Goals of evaluation 319 9.3 Evaluation through expert analysis 320 9.4 Evaluation through user participation 327 9.5 Choosing an evaluation method 357 9.6 Summary 362 Exercises 363 Recommended reading 364 Chapter 10 Universal design 365 10.1 Introduction 366 10.2 Universal design principles 366 10.3 Multi-modal interaction 368 Design Focus: Designing websites for screen readers 374 Design Focus: Choosing the right kind of speech 375 Design Focus: Apple Newton 381 10.4 Designing for diversity 384 Design Focus: Mathematics for the blind 386 10.5 Summary 393 Exercises 393 Recommended reading 394 Chapter 11 User support 395 11.1 Introduction 396 11.2 Requirements of user support 397 11.3 Approaches to user support 399 11.4 Adaptive help systems 404 Design Focus: It’s good to talk – help from real people 405 11.5 Designing user support systems 412 11.6 Summary 414 Exercises 415 Recommended reading 416
- 16. Contents xi MODELS AND THEORIES 417 Chapter 12 Cognitive models 419 12.1 Introduction 420 12.2 Goal and task hierarchies 421 Design Focus: GOMS saves money 424 12.3 Linguistic models 430 12.4 The challenge of display-based systems 434 12.5 Physical and device models 436 12.6 Cognitive architectures 443 12.7 Summary 447 Exercises 448 Recommended reading 448 Chapter 13 Socio-organizational issues and stakeholder requirements 450 13.1 Introduction 451 13.2 Organizational issues 451 Design Focus: Implementing workflow in Lotus Notes 457 13.3 Capturing requirements 458 Design Focus: Tomorrow’s hospital – using participatory design 468 13.4 Summary 472 Exercises 473 Recommended reading 474 Chapter 14 Communication and collaboration models 475 14.1 Introduction 476 14.2 Face-to-face communication 476 Design Focus: Looking real – Avatar Conference 481 14.3 Conversation 483 14.4 Text-based communication 495 14.5 Group working 504 14.6 Summary 507 Exercises 508 Recommended reading 509 Chapter 15 Task analysis 510 15.1 Introduction 511 15.2 Differences between task analysis and other techniques 511 15.3 Task decomposition 512 15.4 Knowledge-based analysis 519 15.5 Entity–relationship-based techniques 525 15.6 Sources of information and data collection 532 15.7 Uses of task analysis 538 Part 3
- 17. xii Contents 15.8 Summary 541 Exercises 542 Recommended reading 543 Chapter 16 Dialog notations and design 544 16.1 What is dialog? 545 16.2 Dialog design notations 547 16.3 Diagrammatic notations 548 Design Focus: Using STNs in prototyping 551 Design Focus: Digital watch – documentation and analysis 563 16.4 Textual dialog notations 565 16.5 Dialog semantics 573 16.6 Dialog analysis and design 582 16.7 Summary 589 Exercises 591 Recommended reading 592 Chapter 17 Models of the system 594 17.1 Introduction 595 17.2 Standard formalisms 595 17.3 Interaction models 608 17.4 Continuous behavior 618 17.5 Summary 624 Exercises 625 Recommended reading 627 Chapter 18 Modeling rich interaction 629 18.1 Introduction 630 18.2 Status–event analysis 631 18.3 Rich contexts 639 18.4 Low intention and sensor-based interaction 649 Design Focus: Designing a car courtesy light 655 18.5 Summary 657 Exercises 658 Recommended reading 659 OUTSIDE THE BOX 661 Chapter 19 Groupware 663 19.1 Introduction 664 19.2 Groupware systems 664 Part 4
- 18. Contents xiii 19.3 Computer-mediated communication 667 Design Focus: SMS in action 673 19.4 Meeting and decision support systems 679 19.5 Shared applications and artifacts 685 19.6 Frameworks for groupware 691 Design Focus: TOWER – workspace awareness 701 19.7 Implementing synchronous groupware 702 19.8 Summary 713 Exercises 714 Recommended reading 715 Chapter 20 Ubiquitous computing and augmented realities 716 20.1 Introduction 717 20.2 Ubiquitous computing applications research 717 Design Focus: Ambient Wood – augmenting the physical 723 Design Focus: Classroom 2000/eClass – deploying and evaluating ubicomp 727 Design Focus: Shared experience 732 20.3 Virtual and augmented reality 733 Design Focus: Applications of augmented reality 737 20.4 Information and data visualization 738 Design Focus: Getting the size right 740 20.5 Summary 745 Exercises 746 Recommended reading 746 Chapter 21 Hypertext, multimedia and the world wide web 748 21.1 Introduction 749 21.2 Understanding hypertext 749 21.3 Finding things 761 21.4 Web technology and issues 768 21.5 Static web content 771 21.6 Dynamic web content 778 21.7 Summary 787 Exercises 788 Recommended reading 788 References 791 Index 817
- 19. xiv Guided tour DESIGN PROCESS In this part, we concentrate on how design practice addresses the critical feature of an interactive system – usability from the human perspective. The chapters in this part promote the purposeful design of more usable interactive systems. We begin in Chapter 5 by introducing the key elements in the interaction design process. These elements are then expanded in later chapters. Chapter 6 discusses the design process in more detail, specifically focussing on the place of user-centered design within a software engineering framework. Chapter 7 high- lights the range of design rules that can help us to specify usable interactive systems, including abstract principles, guidelines and other design representations. In Chapter 8, we provide an overview of implementa- tion support for the programmer of an interactive system. Chapter 9 is concerned with the techniques used to evalu- ate the interactive system to see if it satisfies user needs. Chapter 10 discusses how to design a system to be univer- sally accessible, regardless of age, gender, cultural background or ability. In Chapter 11 we discuss the provision of user support in the form of help systems and documentation. P A R T 2 MODELING RICH INTERACTION OVERVIEW We operate within an ecology of people, physical artifacts and electronic systems, and this rich ecology has recently become more complex as electronic devices invade the workplace and our day-to-day lives. We need methods to deal with these rich interactions. n Status–event analysis is a semi-formal, easy to apply technique that: – classifies phenomena as event or status – embodies naïve psychology – highlights feedback problems in interfaces. n Aspects of rich environments can be incorporated into methods such as task analysis: – other people – information requirements – triggers for tasks – modeling artifacts – placeholders in task sequences. n New sensor-based systems do not require explicit interaction; this means: – new cognitive and interaction models – new design methods – new system architectures. 18 19.3 Computer-mediated communication 675 CuSeeMe Special-purpose video conferencing is still relatively expensive, but low-fidelity desktop video conferencing is now within the reach of many users of desktop computers. Digital video cameras are now inexpensive and easily obtainable. They often come with pre-packaged video phone or video conferencing software. However, the system which has really popularized video conferencing is a web-based tool. CuSeeMe works over the internet allowing participants across the world owning only a basic digital video camera to see and talk to one another. The soft- ware is usually public domain (although there are commercial versions) and the services allowing connection are often free. The limited bandwidth available over long-distance internet links means that video quality and frame rates are low and periodic image break-up may occur. In fact, it is sound break-up which is more problematic. After all, we can talk to one another quite easily with- out seeing one another, but find it very difficult over a noisy phone line. Often participants may see one another’s video image, but actually discuss using a synchronous text-based ‘talk’ program. CuSeeMe – video conferencing on the internet. Source: Courtesy of Geoff Ellis 440 Chapter 12 n Cognitive models Worked exercise Do a keystroke-level analysis for opening up an application in a visual desktop interface using a mouse as the pointing device, comparing at least two different methods for performing the task. Repeat the exercise using a trackball. Consider how the analysis would differ for various positions of the trackball relative to the keyboard and for other pointing devices. Answer We provide a keystroke-level analysis for three different methods for launching an application on a visual desktop. These methods are analyzed for a conventional one- button mouse, a trackball mounted away from the keyboard and one mounted close to the keyboard. The main distinction between the two trackballs is that the second one does not require an explicit repositioning of the hands, that is there is no time required for homing the hands between the pointing device and the keyboard. Method 1 Double clicking on application icon Steps Operator Mouse Trackball1 Trackball2 1. Move hand to mouse H[mouse] 0.400 0.400 0.000 2. Mouse to icon P[to icon] 0.664 1.113 1.113 3. Double click 2B[click] 0.400 0.400 0.400 4. Return to keyboard H[kbd] 0.400 0.400 0.000 Total times 1.864 2.313 1.513 Method 2 Using an accelerator key Steps Operator Mouse Trackball1 Trackball2 1. Move hand to mouse H[mouse] 0.400 0.400 0.000 2. Mouse to icon P[to icon] 0.664 1.113 1.113 3. Click to select B[click] 0.200 0.200 0.200 4. Pause M 1.350 1.350 1.350 5. Return to keyboard H[kbd] 0.400 0.400 0.000 6. Press accelerator K 0.200 0.200 0.200 Total times 3.214 3.663 2.763 Method 3 Using a menu Steps Operator Mouse Trackball1 Trackball2 1. Move hand to mouse H[mouse] 0.400 0.400 0.000 2. Mouse to icon P[to icon] 0.664 1.113 1.113 3. Click to select B[click] 0.200 0.200 0.200 4. Pause M 1.350 1.350 1.350 5. Mouse to file menu P 0.664 1.113 1.113 6. Pop-up menu B[down] 0.100 0.100 0.100 7. Drag to open P[drag] 0.713 1.248 1.248 8. Release mouse B[up] 0.100 0.100 0.100 9. Return to keyboard H[kbd] 0.400 0.400 0.000 Total times 4.591 6.024 5.224 The part structure separates out introductory and more advanced material, with each part opener giving a simple description of what its constituent chapters cover Bullet points at the start of each chapter highlight the core coverage Worked exercises within chapters provide step-by-step guidelines to demonstrate problem-solving techniques Boxed asides contain descriptions of particular tasks or technologies for additional interest, experimentation and discussion
- 20. Guided tour xv 732 Chapter 20 n Ubiquitous computing and augmented realities within these environments. Much of our understanding of work has developed from Fordist and Taylorist principles on the structuring of activities and tasks. Evaluation within HCI reflects these roots and is often predicated on notions of task and the measurement of performance and efficiency in meeting these goals and tasks. However, it is not clear that these measures can apply universally across activities when we move away from structured and paid work to other activities. For example, DESIGN FOCUS Shared experience You are in the Mackintosh Interpretation Centre in an arts center in Glasgow, Scotland. You notice a man wearing black wandering around looking at the exhibits and then occasionally at a small PDA he is holding. As you get closer he appears to be talking to himself, but then you realize he is simply talking into a head-mounted microphone. ‘Some people can never stop using their mobile phone’, you think. As you are looking at one exhibit, he comes across and suddenly cranes forward to look more closely, getting right in front of you. ‘How rude’, you think. The visitor is taking part in the City project – a mixed-reality experience. He is talking to two other people at remote sites, one who has a desktop VR view of the exhibition and the other just a website. However, they can all see representations of each other. The visitor is being tracked by ultrasound and he appears in the VR world. Also, the web user’s current page locates her in a particular part of the virtual exhibition. All of the users see a map of the exhibitiion showing where they all are. You might think that in such an experiment the person actually in the museum would take the lead, but in fact real groups using this system seemed to have equal roles and really had a sense of shared experi- ence despite their very different means of seeing the exhibition. See the book website for a full case study: /e3/casestudy/city/ City project: physical presence, VR interfaces and web interface. Source: Courtesy of Matthew Chalmers, note: City is an Equator project Recommended reading 509 RECOMMENDED READING J. Carroll, editor, HCI Models, Theories, and Frameworks: Toward an Interdisciplinary Science, Morgan Kaufmann, 2003. See chapters by Perry on distributed cognition, Monk on common ground and Kraut on social psychology. L. A. Suchman, Plans and Situated Actions: The Problem of Human–Machine Communication, Cambridge University Press, 1987. This book popularized ethnography within HCI. It puts forward the viewpoint that most actions are not pre-planned, but situated within the context in which they occur. The principal domain of the book is the design of help for a photo- copier. This is itself a single-user task, but the methodology applied is based on both ethnographic and conversational analysis. The book includes several chap- ters discussing the contextual nature of language and analysis of conversation transcripts. T. Winograd and F. Flores, Understanding Computers and Cognition: A New Foundation for Design, Addison-Wesley, 1986. Like Suchman, this book emphasizes the contextual nature of language and the weakness of traditional artificial intelligence research. It includes an account of speech act theory as applied to Coordinator. Many people disagree with the authors’ use of speech act theory, but, whether by application or reaction, this work has been highly influential. S. Greenberg, editor, Computer-supported Cooperative Work and Groupware, Academic Press, 1991. The contents of this collection originally made up two special issues of the International Journal of Man–Machine Studies. In addition, the book contains Greenberg’s extensive annotated bibliography of CSCW, a major entry point for any research into the field. Updated versions of the bibliography can be obtained from the Department of Computer Science, University of Calgary, Calgary, Alberta, Canada. Communications of the ACM, Vol. 34, No. 12, special issue on ‘collaborative com- puting’, December 1991. Several issues of the journal Interacting with Computers from late 1992 through early 1993 have a special emphasis on CSCW. Computer-Supported Cooperative Work is a journal dedicated to CSCW. See also back issues of the journal Collaborative Computing. This ran independently for a while, but has now merged with Computer-Supported Cooperative Work. See also the recommended reading list for Chapter 19, especially the conference proceedings. Exercises 393 SUMMARY Universal design is about designing systems that are accessible by all users in all circumstances, taking account of human diversity in disabilities, age and culture. Universal design helps everyone – for example, designing a system so that it can be used by someone who is deaf or hard of hearing will benefit other people working in noisy environments or without audio facilities. Designing to be accessible to screen- reading systems will make websites better for mobile users and older browsers. Multi-modal systems provide access to system information and functionality through a range of different input and output channels, exploiting redundancy. Such systems will enable users with sensory, physical or cognitive impairments to make use of the channels that they can use most effectively. But all users benefit from multi-modal systems that utilize more of our senses in an involving interactive experience. For any design choice we should ask ourselves whether our decision is excluding someone and whether there are any potential confusions or misunderstandings in our choice. 10.5 EXERCISES 10.1 Is multi-modality always a good thing? Justify your answer. 10.2 What are (i) auditory icons and (ii) earcons? How can they be used to benefit both visually impaired and sighted users? 10.3 Research your country’s legislation relating to accessibility of technology for disabled people. What are the implications of this to your future career in computing? 10.4 Take your university website or another site of your choice and assess it for accessibility using Bobby. How would you recommend improving the site? 10.5 How could systems be made more accessible to older users? 10.6 Interview either (i) a person you know over 65 or (ii) a child you know under 16 about their experience, attitude and expectations of computers. What factors would you take into account if you were designing a website aimed at this person? 10.7 Use the screen reader simulation available at www.webaim.org/simulations/screenreader to experience something of what it is like to access the web using a screen reader. Can you find the answers to the test questions on the site? Annotated further reading encourages readers to research topics in depth Design Focus mini case studies highlight practical applications of HCI concepts Frequent links to the book website for further information Chapter summaries reinforce student learning. Exercises at the end of chapters can be used by teachers or individuals to test understanding
- 21. FOREWORD Human–computer interaction is a difficult endeavor with glorious rewards. Designing interactive computer systems to be effective, efficient, easy, and enjoyable to use is important, so that people and society may realize the benefits of computation- based devices. The subtle weave of constraints and their trade-offs – human, machine, algorithmic, task, social, aesthetic, and economic – generates the difficulty. The reward is the creation of digital libraries where scholars can find and turn the pages of virtual medieval manuscripts thousands of miles away; medical instruments that allow a surgical team to conceptualize, locate, and monitor a complex neuro- surgical operation; virtual worlds for entertainment and social interaction, respon- sive and efficient government services, from online license renewal to the analysis of parliamentary testimony; or smart telephones that know where they are and under- stand limited speech. Interaction designers create interaction in virtual worlds and embed interaction in physical worlds. Human–computer interaction is a specialty in many fields, and is therefore multi- disciplinary, but it has an intrinsic relationship as a subfield to computer science. Most interactive computing systems are for some human purpose and interact with humans in human contexts. The notion that computer science is the study of algo- rithms has virtue as an attempt to bring foundational rigor, but can lead to ignoring constraints foundational to the design of successful interactive computer systems. A lesson repeatedly learned in engineering is that a major source of failure is the narrow optimization of a design that does not take sufficient account of contextual factors. Human users and their contexts are major components of the design problem that cannot be wished away simply because they are complex to address. In fact, that largest part of program code in most interactive systems deals with user interaction. Inadequate attention to users and task context not only leads to bad user interfaces, it puts entire systems at risk. The problem is how to take into account the human and contextual part of a sys- tem with anything like the rigor with which other parts of the system are understood and designed – how to go beyond fuzzy platitudes like ‘know the user’ that are true, but do not give a method for doing or a test for having done. This is difficult to do, but inescapable, and, in fact, capable of progress. Over the years, the need to take into account human aspects of technical systems has led to the creation of new fields of study: applied psychology, industrial engineering, ergonomics, human factors,
- 22. Foreword xvii man–machine systems. Human–computer interaction is the latest of these, more complex in some ways because of the breadth of user populations and applications, the reach into cognitive and social constraints, and the emphasis on interaction. The experiences with other human-technical disciplines lead to a set of conclusions about how a discipline of human–computer interaction should be organized if it is to be successful. First, design is where the action is. An effective discipline of human–computer interaction cannot be based largely on ‘usability analysis’, important though that may be. Usability analysis happens too late; there are too few degrees of freedom; and most importantly, it is not generative. Design thrives on understanding constraints, on insight into the design space, and on deep knowledge of the materials of the design, that is, the user, the task, and the machine. The classic landmark designs in human–computer interaction, such as the Xerox Star and the Apple Lisa/Macintosh, were not created from usability analysis (although usability analysis had important roles), but by generative principles for their designs by user interface designers who had control of the design and implementation. Second, although the notion of ‘user-centered design’ gets much press, we should really be emphasizing ‘task-centered design’. Understanding the purpose and con- text of a system is key to allocating functions between people and machines and to designing their interaction. It is only in deciding what a human–machine system should do and the constraints on this goal that the human and technical issues can be resolved. The need for task-centered design brings forward the need for methods of task analysis as a central part of system design. Third, human–computer interaction needs to be structured to include both analytic and implementation methods together in the same discipline and taught together as part of the core. Practitioners of the discipline who can only evaluate, but not design and build are under a handicap. Builders who cannot reason analytically about the systems they build or who do not understand the human information pro- cessing or social contexts of their designs are under a handicap. Of course, there will be specialists in one or another part of human–computer interaction, but for there to be a successful field, there must be a common core. Finally, what makes a discipline is a set of methods for doing something. A field must have results that can be taught and used by people other than their originators to do something. Historically, a field naturally evolves from a set of point results to a set of techniques to a set of facts, general abstractions, methods, and theories. In fact, for a field to be cumulative, there must be compaction of knowledge by crunch- ing the results down into methods and theories; otherwise the field becomes fad- driven and a collection of an almost unteachably large set of weak results. The most useful methods and theories are generative theories: from some task analysis it is possible to compute some insightful property that constrains the design space of a system. In a formula: task analysis, approximation, and calculation. For example, we can predict that if a graphics system cannot update the display faster than 10 times/second then the illusion of animation will begin to break down. This con- straint worked backwards has architectural implications for how to guarantee the needed display rate under variable computational load. It can be designed against.
- 23. xviii Foreword This textbook, by Alan Dix, Janet Finlay, Gregory Abowd, and Russell Beale, represents how far human–computer interaction has come in developing and organizing technical results for the design and understanding of interactive systems. Remarkably, by the light of their text, it is pretty far, satisfying all the just- enumerated conclusions. This book makes an argument that by now there are many teachable results in human–computer interaction by weight alone! It makes an argu- ment that these results form a cumulative discipline by its structure, with sections that organize the results systematically, characterizing human, machine, interaction, and the design process. There are analytic models, but also code implementation examples. It is no surprise that methods of task analysis play a prominent role in the text as do theories to help in the design of the interaction. Usability evaluation methods are integrated in their proper niche within the larger framework. In short, the codification of the field of human–computer interaction in this text is now starting to look like other subfields of computer science. Students by studying the text can learn how to understand and build interactive systems. Human–computer interaction as represented by the text fits together with other parts of computer science. Moreover, human–computer interaction as presented is a challenge problem for advancing theory in cognitive science, design, business, or social-technical systems. Given where the field was just a few short years ago, the creation of this text is a monumental achievement. The way is open to reap the glorious rewards of interactive systems through a markedly less difficult endeavor, both for designer and for user. Stuart K. Card Palo Alto Research Center, Palo Alto, California
- 24. PREFACE TO THE THIRD EDITION It is ten years since the first edition of this book was published and much has changed. Ubiquitous computing and rich sensor-filled environments are finding their way out of the laboratory, not just into films and fiction, but also into our workplaces and homes. Now the computer really has broken its bounds of plastic and glass: we live in networked societies where personal computing devices from mobile phones to smart cards fill our pockets, and electronic devices surround us at home and at work. The web too has grown from a largely academic network into the hub of business and everyday lives. As the distinctions between physical and digital, work and leisure start to break down, human–computer interaction is also radically changing. We have tried to capture some of the excitement of these changes in this revised edition, including issues of physical devices in Chapters 2 and 3, discussion of web interfaces in Chapter 21, ubiquitous computing in Chapters 4 and 20, and new models and paradigms for interaction in these new environments in Chapters 17 and 18. We have reflected aspects of the shift in use of technology from work to leisure in the analysis of user experience in Chapter 3, and in several of the boxed examples and case studies in the text. This new edition of Human–Computer Interaction is not just tracking these changes but looking ahead at emerging areas. However, it is also rooted in strong principles and models that are not dependent on the passing technologies of the day. We are excited both by the challenges of the new and by the established foundations, as it is these foundations that will be the means by which today’s students understand tomorrow’s technology. So we make no apology for continuing the focus of previous editions on the theoretical and con- ceptual models that underpin our discipline. As the use of technology has changed, these models have expanded. In particular, the insular individual focus of early work is increasingly giving way to include the social and physical context. This is reflected in the expanded treatment of social and organizational analysis, including ethnography, in Chapter 13, and the analysis of artifacts in the physical environment in Chapter 18.
- 25. xx Preface to the third edition STRUCTURE The structure of the new edition has been completely revised. This in part reflects the growth of the area: ten years ago HCI was as often as not a minority optional sub- ject, and the original edition was written to capture the core material for a standard course. Today HCI is much expanded: some areas (like CSCW) are fully fledged dis- ciplines in their own right, and HCI is studied from a range of perspectives and at different levels of detail. We have therefore separated basic material suitable for intro- ductory courses into the first two parts, including a new chapter on interaction design, which adds new material on scenarios and navigation design and provides an overview suitable for a first course. In addition, we have included a new chapter on universal design, to reflect the growing emphasis on design that is inclusive of all, regardless of ability, age or cultural background. More advanced material focussing on different HCI models and theories is presented in Part 3, with extended cover- age of social and contextual models and rich interaction. It is intended that these sections will be suitable for more advanced HCI courses at undergraduate and postgraduate level, as well as for researchers new to the field. Detailed coverage of the particular domains of web applications, ubiquitous computing and CSCW is given in Part 4. New to this edition is a full color plate section. Images flagged with a camera icon in the text can be found in color in the plate section. WEBSITE AND SUPPORT MATERIALS We have always believed that support materials are an essential part of a textbook of this kind. These are designed to supplement and enhance the printed book – phys- ical and digital integration in practice. Since the first edition we have had exercises, mini-case studies and presentation slides for all chapters available electronically. For the second edition these were incorporated into a website including links and an online search facility that acts as an exhaustive index to the book and mini- encyclopedia of HCI. For visually disabled readers, access to a full online electronic text has also been available. The website is continuing to develop, and for the third edition provides all these features plus more, including WAP search, multi-choice questions, and extended case study material (see also color plate section). We will use the book website to bring you new exercises, information and other things, so do visit us at www.hcibook.com (also available via www.booksites.net/dix). Throughout the book you will find shorthand web references of the form /e3/a-page-url/. Just prepend http://www.hcibook.com to find further information. To assist users of the second edition, a mapping between the structures of the old and new editions is available on the web at: http://www.hcibook.com/e3/contents/map2e/
- 26. Preface to the third edition xxi STYLISTIC CONVENTION As with all books, we have had to make some global decisions regarding style and terminology. Specifically, in a book in which the central characters are ‘the user’ and ‘the designer’, it is difficult to avoid the singular pronoun. We therefore use the pronoun ‘he’ when discussing the user and ‘she’ when referring to the designer. In other cases we use ‘she’ as a generic term. This should not be taken to imply anything about the composition of any actual population. Similarly, we have adopted the convention of referring to the field of ‘Human– Computer Interaction’ and the notion of ‘human–computer interaction’. In many cases we will also use the abbreviation HCI. ACKNOWLEDGEMENTS In a book of this size, written by multiple authors, there will always be myriad people behind the scenes who have aided, supported and abetted our efforts. We would like to thank all those who provided information, pictures and software that have enhanced the quality of the final product. In particular, we are indebted to Wendy Mackay for the photograph of EVA; Wendy Hall and her colleagues at the University of Southampton for the screen shot of Microcosm; Saul Greenberg for the reactive keyboard; Alistair Edwards for Soundtrack; Christina Engelbart for the photographs of the early chord keyset and mouse; Geoff Ellis for the screen shot of Devina and himself using CuSeeMe; Steve Benford for images of the Internet Foyer; and Tony Renshaw who provided photographs of the eye tracking equipment. Thanks too to Simon Shum for information on design rationale, Robert Ward who gave us material on psycho-physiology, and Elizabeth Mynatt and Tom Rodden who worked with Gregory on material adapted in Chapter 20. Several of the boxed case studies are based on the work of multi-institution projects, and we are grateful to all those from the project teams of CASCO, thePooch SMART-ITS, TOWER, AVATAR-Conference and TEAM-HOS for boxes and case studies based on their work; and also to the EQUATOR project from which we drew material for the boxes on cultural probes, ‘Ambient Wood’ and ‘City’. We would also like to thank all the reviewers and survey respondents whose feedback helped us to select our subject matter and improve our coverage; and our colleagues at our respective institutions and beyond who offered insight, encouragement and tolerance throughout the revi- sion. We are indebted to all those who have contributed to the production process at Pearson Education and elsewhere, especially Keith Mansfield, Anita Atkinson, Lynette Miller, Sheila Chatten and Robert Chaundy. Personal thanks must go to Fiona, Esther, Miriam, Rachel, Tina, Meghan, Aidan and Blaise, who have all endured ‘The Book’ well beyond the call of duty and over
- 27. xxii Preface to the third edition many years, and Bruno and ‘the girls’ who continue to make their own inimitable contribution. Finally we all owe huge thanks to Fiona for her continued deep personal support and for tireless proofreading, checking of figures, and keeping us all moving. We would never have got beyond the first edition without her. The efforts of all of these have meant that the book is better than it would other- wise have been. Where it could still be better, we take full responsibility.
- 28. PUBLISHER’S ACKNOWLEDGEMENTS We are grateful to the following for permission to reproduce copyright material: Figure p. 2, Figures 3.14, 3.15, 3.16 and 5.13 and Exercise 8.4 screen shots reprinted by permission from Apple Computer, Inc.; Figure 2.11 reprinted by permission of Keith Cheverst; Figure 3.13 from The WebBook and Web Forager: An information workspace for the world-wide web in CHI Conference Proceedings, © 1996 ACM, Inc., reprinted by permission (Card, S. K., Robertson, G. G. and York, W. 1996); Figures 3.9, 3.19, 5.5, Chapter 14, Design Focus: Looking real – Avatar Conference screen shots, Figures 21.3, 21.10, 21.11 screen shot frames reprinted by permission from Microsoft Corporation; Tables 6.2 and 6.3 adapted from Usability engineering: our experience and evolution in Handbook for Human–Computer Interaction edited by M. Helander, Copyright 1988, with permission from Elsevier (Whiteside, J., Bennett, J. and Hotzblatt, K. 1988); Figure 7.1 adapted from The alternate reality kit – an animated environment for creating interactive simulations in Proceedings of Workshop on Visual Languages, © 1986 IEEE, reprinted by permission of IEEE (Smith, R. B. 1986); Figure 7.2 from Guidelines for designing user interface software in MITRE Corporation Report MTR-9420, reprinted by permission of The MITRE Corporation (Smith, S. L. and Mosier, J. N. 1986); Figure 7.3 reprinted by permis- sion of Jenifer Tidwell; Figures 8.6 and 8.9 from Xview Programming Manual, Volume 7 of The X Window System, reprinted by permission of O’Reilly and Associates, Inc. (Heller, D. 1990); Figure 9.8 screen shot reprinted by permission of Dr. R. D. Ward; Figure 10.2 after Earcons and icons: their structure and common design principles in Human-Computer Interaction, 4(1), published and reprinted by permission of Lawrence Erlbaum Associates, Inc. (Blattner, M., Sumikawa, D. and Greenberg, R. 1989); Figure 10.5 reprinted by permission of Alistair D. N. Edwards; Figure 10.7 reprinted by permission of Saul Greenberg; Figure 11.2 screen shot reprinted by permission of Macromedia, Inc.; Table 12.1 adapted from The Psychology of Human Computer Interaction, published and reprinted by permission of Lawrence Erlbaum Associates, Inc. (Card, S. K., Moran, T. P. and Newell, A. 1983); Table 12.2 after Table in A comparison of input devices in elemental pointing and dragging tasks in Reaching through technology – CHI’91 Conference Proceedings, Human Factors in Computing Systems, April, edited by S. P. Robertson, G. M. Olson and J. S. Olson, © 1991 ACM, Inc., reprinted by permission (Mackenzie,
- 29. xxiv Publisher’s acknowledgements I. S., Sellen, A. and Buxton, W. 1991); Figure 14.1 from Understanding Computers and Cognition: A New Foundation for Design, published by Addison-Wesley, reprinted by permission of Pearson Education, Inc. (Winograd, T. and Flores, F. 1986); Figure 14.5 from Theories of multi-party interaction. Technical report, Social and Computer Sciences Research Group, University of Surrey and Queen Mary and Westfield Colleges, University of London, reprinted by permission of Nigel Gilbert (Hewitt, B., Gilbert, N., Jirotka, M. and Wilbur, S. 1990); Figure 14.6 from Dialogue processes in computer-mediated communication: a study of letters in the com system. Technical report, Linköping Studies in Arts and Sciences, reprinted by permission of Kerstin Severinson Eklundh (Eklundh, K. S. 1986); Chapter 14, Design Focus: Looking real – Avatar Conference, screen shots reprinted by permission of AVATAR-Conference project team; Figure 16.17 screen shot reprinted by permis- sion of Harold Thimbleby; Figure 17.5 based on Verifying the behaviour of virtual world objects in DSV-IS 2000 Interactive Systems: Design, Specification and Verification. LNCS 1946, edited by P. Palanque and F. Paternò, published and reprinted by permission of Spinger-Verlag GmbH & Co. KG (Willans, J. S. and Harrison, M. D. 2001); Figure 18.4 icons reprinted by permission of Fabio Paternò; Chapter 19, p.675 CuSeeMe screen shot reprinted by permission of Geoff Ellis; Chapter 19, Design Focus: TOWER – workspace awareness, screen shots reprinted by permission of Wolfgang Prinz; Figure 20.1 reprinted by permission of Mitsubishi Electric Research Laboratories, Inc.; Figure 20.4 (right) reprinted by permission of Sony Computer Science Laboratories, Inc; Figure 20.9 from Cone trees. Animated 3d visualisation of hierarchical information in Proceedings of the CH’91 Conference of Human Factors in Computing Systems, © 1991 ACM, Inc., reprinted by permission (Robertson, G. G., Card, S. K., and Mackinlay, J. D. 1991); Figure 20.10 from Lifelines: visualising personal histories in Proceedings of CH’96, © 1996 ACM, Inc., reprinted by permission (Plaisant, C., Milash, B., Rose, A., Widoff, S. and Shneiderman, B. 1996); Figure 20.11 from Browsing anatomical image databases: a case study of the Visible Human in CH’96 Conference Companion, © 1996 ACM, Inc., reprinted by permission (North, C. and Korn, F. 1996); Figure 20.12 from Externalising abstract mathematical models in Proceedings of CH’96, © 1996 ACM, Inc., reprinted by permission (Tweedie, L., Spence, R., Dawkes, H. and Su, H. 1996); Figure 21.2 from The impact of Utility and Time on Distributed Information Retrieval in People and Computers XII: Proceedings of HCI’97, edited by H. Thimbleby, B. O’Conaill and P. Thomas, published and reprinted by permission of Spinger-Verlag GmbH & Co. KG (Johnson, C. W. 1997); Figure 21.4 screen shot reprinted by permission of the Departments of Electronics and Computer Science and History at the University of Southampton; Figure 21.6 Netscape browser window © 2002 Netscape Communications Corporation. Used with permission. Netscape has not authorized, sponsored, endorsed, or approved this publication and is not responsible for its content. We are grateful to the following for permission to reproduce photographs: Chapter 1, p. 50, Popperfoto.com; Chapter 2, p. 65, PCD Maltron Ltd; Figure 2.2 Electrolux; Figures 2.6 and 19.6 photos courtesy of Douglas Engelbart and Bootstrap Institute; Figure 2.8 (left) British Sky Broadcasting Limited; Figure 2.13 (bottom
- 30. Publisher’s acknowledgements xxv right) Sony (UK) Ltd; Chapter 2, Design Focus: Feeling the Road, BMW AG; Chapter 2, Design Focus: Smart-Its – making using sensors easy, Hans Gellersen; Figures 4.1 (right) and 20.2 (left) Palo Alto Research Center; Figure 4.2 and 20.3 (left) François Guimbretière; Figure 4.3 (bottom left) Franklin Electronic Publishers; Figure 5.2 (top plate and middle plate) Kingston Museum and Heritage Service, (bottom plate) V&A Images, The Victoria and Albert Museum, London; Chapter 5, Design Focus: Cultural probes, William W. Gaver, Anthony Boucher, Sarah Pennington and Brendan Walker, Equator IRC, Royal College of Art; Chapter 6, p. 245, from The 1984 Olympic Message System: a text of behavioural principle of system design in Communications of the ACM, 30(9), © 1987 ACM, Inc., reprinted by permission (Gould, J. D., Boies, S. J., Levy, S., Richards, J. T. and Schoonard, J. 1987); Figures 9.5 and 9.6 J. A. Renshaw; Figure 9.7 Dr. R. D. Ward; Figure 10.3 SensAble Technologies; Chapter 13, Design Focus: Tomorrow’s hospital – using participatory design, Professor J. Artur Vale Serrano; Chapter 18, p. 650, Michael Beigl; Chapter 19, p. 678, Steve Benford, The Mixed Reality Laboratory, University of Nottingham; Chapter 19, Design Focus: SMS in action, Mark Rouncefield; Figure 20.2 (right) Ken Hinckley; Figure 20.3 (right) MIT Media Lab; Figure 20.4 (left) from Interacting with paper on the digital desk in Communications of the ACM, 36(7), © 1993 ACM, Inc., reprinted by permission (Wellner, P. 1993); Chapter 20, p. 726, Peter Phillips; Chapter 20, Design Focus: Ambient wood – augmenting the physical, Yvonne Rogers; Chapter 20, Design Focus: Shared experience, Matthew Chalmers. We are grateful to the following for permission to reproduce text extracts: Pearson Education, Inc. Publishing as Pearson Addison Wesley for an extract adapted from Designing the User Interface: Strategies for Effective Human–Computer Interaction 3/e by B. Shneiderman © 1998, Pearson Education, Inc; Perseus Books Group for an extract adapted from The Design of Everyday Things by D. Norman, 1998; and Wiley Publishing, Inc. for extracts adapted from ‘Heuristic Evaluation’ by Jakob Nielson and Robert L. Mack published in Usability Inspection Methods © 1994 Wiley Publishing, Inc.; IEEE for permission to base chapter 20 on ‘The human ex- perience’ by Gregory Abowd, Elizabeth Mynatt and Tom Rodden which appeared in IEEE Pervasive Computing Magazine, Special Inaugural Issue on Reaching for Weiser’s Vision, Vol. 1, Issue 1, pp. 48–58, Jan–March 2002. © 2002 IEEE. In some instances we have been unable to trace the owners of copyright material, and we would appreciate any information that would enable us to do so.
- 32. INTRODUCTION WHY HUMAN–COMPUTER INTERACTION? In the first edition of this book we wrote the following: This is the authors’ second attempt at writing this introduction. Our first attempt fell victim to a design quirk coupled with an innocent, though weary and less than attentive, user. The word-processing package we originally used to write this intro- duction is menu based. Menu items are grouped to reflect their function. The ‘save’ and ‘delete’ options, both of which are correctly classified as file-level operations, are consequently adjacent items in the menu. With a cursor controlled by a trackball it is all too easy for the hand to slip, inadvertently selecting delete instead of save. Of course, the delete option, being well thought out, pops up a confirmation box allow- ing the user to cancel a mistaken command. Unfortunately, the save option produces a very similar confirmation box – it was only as we hit the ‘Confirm’ button that we noticed the word ‘delete’ at the top . . . Happily this word processor no longer has a delete option in its menu, but unfortu- nately, similar problems to this are still an all too common occurrence. Errors such as these, resulting from poor design choices, happen every day. Perhaps they are not catastrophic: after all nobody’s life is endangered nor is there environmental damage (unless the designer happens to be nearby or you break something in frustration!). However, when you lose several hours’ work with no written notes or backup and a publisher’s deadline already a week past, ‘catastrophe’ is certainly the word that springs to mind. Why is it then that when computers are marketed as ‘user friendly’ and ‘easy to use’, simple mistakes like this can still occur? Did the designer of the word processor actually try to use it with the trackball, or was it just that she was so expert with the system that the mistake never arose? We hazard a guess that no one tried to use it when tired and under pressure. But these criticisms are not levied only on the design- ers of traditional computer software. More and more, our everyday lives involve pro- grammed devices that do not sit on our desk, and these devices are just as unusable. Exactly how many VCR designers understand the universal difficulty people have trying to set their machines to record a television program? Do car radio designers
- 33. 2 Introduction actually think it is safe to use so many knobs and displays that the driver has to divert attention away from the road completely in order to tune the radio or adjust the volume? Computers and related devices have to be designed with an understanding that people with specific tasks in mind will want to use them in a way that is seamless with respect to their everyday work. To do this, those who design these systems need to know how to think in terms of the eventual users’ tasks and how to translate that knowledge into an executable system. But there is a problem with trying to teach the notion of designing computers for people. All designers are people and, most prob- ably, they are users as well. Isn’t it therefore intuitive to design for the user? Why does it need to be taught when we all know what a good interface looks like? As a result, the study of human–computer interaction (HCI) tends to come late in the designer’s training, if at all. The scenario with which we started shows that this is a mistaken view; it is not at all intuitive or easy to design consistent, robust systems DESIGN FOCUS Things don’t change It would be nice to think that problems like those described at the start of the Introduction would never happen now. Think again! Look at the MacOS X ‘dock’ below. It is a fast launch point for applica- tions; folders and files can be dragged there for instant access; and also, at the right-hand side, there sits the trash can. Imagine what happens as you try to drag a file into one of the folders. If your finger accidentally slips whilst the icon is over the trash can – oops! Happily this is not quite as easy in reality as it looks in the screen shot, since the icons in the dock con- stantly move around as you try to drag a file into it. This is to make room for the file in case you want to place it in the dock. However, it means you have to concentrate very hard when dragging a file over the dock. We assume this is not a deliberate feature, but it does have the beneficial side effect that users are less likely to throw away a file by accident – whew! In fact it is quite fun to watch a new user trying to throw away a file. The trash can keeps moving as if it didn’t want the file in it. Experienced users evolve coping strategies. One user always drags files into the trash from the right-hand side as then the icons in the dock don’t move around. So two lessons: n designs don’t always get better n but at least users are clever. Screen shot reprinted by permission from Apple Computer, Inc.
- 34. that will cope with all manner of user carelessness. The interface is not something that can be plugged in at the last minute; its design should be developed integrally with the rest of the system. It should not just present a ‘pretty face’, but should sup- port the tasks that people actually want to do, and forgive the careless mistakes. We therefore need to consider how HCI fits into the design process. Designing usable systems is not simply a matter of altruism towards the eventual user, or even marketing; it is increasingly a matter of law. National health and safety standards constrain employers to provide their workforce with usable computer sys- tems: not just safe but usable. For example, EC Directive 90/270/EEC, which has been incorporated into member countries’ legislation, requires employers to ensure the following when designing, selecting, commissioning or modifying software: n that it is suitable for the task n that it is easy to use and, where appropriate, adaptable to the user’s knowledge and experience n that it provides feedback on performance n that it displays information in a format and at a pace that is adapted to the user n that it conforms to the ‘principles of software ergonomics’. Designers and employers can no longer afford to ignore the user. WHAT IS HCI? The term human–computer interaction has only been in widespread use since the early 1980s, but has its roots in more established disciplines. Systematic study of human performance began in earnest at the beginning of the last century in factories, with an emphasis on manual tasks. The Second World War provided the impetus for studying the interaction between humans and machines, as each side strove to pro- duce more effective weapons systems. This led to a wave of interest in the area among researchers, and the formation of the Ergonomics Research Society in 1949. Tradi- tionally, ergonomists have been concerned primarily with the physical characteristics of machines and systems, and how these affect user performance. Human Factors incorporates these issues, and more cognitive issues as well. The terms are often used interchangeably, with Ergonomics being the preferred term in the United Kingdom and Human Factors in the English-speaking parts of North America. Both of these disciplines are concerned with user performance in the context of any system, whether computer, mechanical or manual. As computer use became more widespread, an increasing number of researchers specialized in studying the interaction between people and computers, concerning themselves with the physical, psychological and theoretical aspects of this process. This research originally went under the name man– machine interaction, but this became human–computer interaction in recognition of the particular interest in computers and the composition of the user population! Another strand of research that has influenced the development of HCI is infor- mation science and technology. Again the former is an old discipline, pre-dating the introduction of technology, and is concerned with the management and manipulation What is HCI? 3
- 35. 4 Introduction of information within an organization. The introduction of technology has had a profound effect on the way that information can be stored, accessed and utilized and, consequently, a significant effect on the organization and work environment. Systems analysis has traditionally concerned itself with the influence of technology in the workplace, and fitting the technology to the requirements and constraints of the job. These issues are also the concern of HCI. HCI draws on many disciplines, as we shall see, but it is in computer science and systems design that it must be accepted as a central concern. For all the other discip- lines it can be a specialism, albeit one that provides crucial input; for systems design it is an essential part of the design process. From this perspective, HCI involves the design, implementation and evaluation of interactive systems in the context of the user’s task and work. However, when we talk about human–computer interaction, we do not necessarily envisage a single user with a desktop computer. By user we may mean an individual user, a group of users working together, or a sequence of users in an organization, each dealing with some part of the task or process. The user is whoever is trying to get the job done using the technology. By computer we mean any technology ranging from the general desktop computer to a large-scale computer system, a process control system or an embedded system. The system may include non-computerized parts, including other people. By interaction we mean any communication between a user and computer, be it direct or indirect. Direct interaction involves a dialog with feedback and control throughout performance of the task. Indirect interaction may involve batch processing or intelligent sensors controlling the environment. The important thing is that the user is interacting with the computer in order to accomplish something. WHO IS INVOLVED IN HCI? HCI is undoubtedly a multi-disciplinary subject. The ideal designer of an interactive system would have expertise in a range of topics: psychology and cognitive science to give her knowledge of the user’s perceptual, cognitive and problem-solving skills; ergonomics for the user’s physical capabilities; sociology to help her under- stand the wider context of the interaction; computer science and engineering to be able to build the necessary technology; business to be able to market it; graphic design to produce an effective interface presentation; technical writing to produce the manuals, and so it goes on. There is obviously too much expertise here to be held by one person (or indeed four!), perhaps even too much for the average design team. Indeed, although HCI is recognized as an interdisciplinary subject, in practice peo- ple tend to take a strong stance on one side or another. However, it is not possible to design effective interactive systems from one discipline in isolation. Input is needed from all sides. For example, a beautifully designed graphic display may be unusable if it ignores dialog constraints or the psychological limitations of the user.
- 36. Theory and HCI 5 In this book we want to encourage the multi-disciplinary view of HCI but we too have our ‘stance’, as computer scientists. We are interested in answering a particular question. How do principles and methods from each of these contributing dis- ciplines in HCI help us to design better systems? In this we must be pragmatists rather than theorists: we want to know how to apply the theory to the problem rather than just acquire a deep understanding of the theory. Our goal, then, is to be multi-disciplinary but practical. We concentrate particularly on computer science, psychology and cognitive science as core subjects, and on their application to design; other disciplines are consulted to provide input where relevant. THEORY AND HCI Unfortunately for us, there is no general and unified theory of HCI that we can present. Indeed, it may be impossible ever to derive one; it is certainly out of our reach today. However, there is an underlying principle that forms the basis of our own views on HCI, and it is captured in our claim that people use computers to accomplish work. This outlines the three major issues of concern: the people, the computers and the tasks that are performed. The system must support the user’s task, which gives us a fourth focus, usability: if the system forces the user to adopt an unacceptable mode of work then it is not usable. There are, however, those who would dismiss our concentration on the task, saying that we do not even know enough about a theory of human tasks to support them in design. There is a good argument here (to which we return in Chapter 15). However, we can live with this confusion about what real tasks are because our understanding of tasks at the moment is sufficient to give us direction in design. The user’s current tasks are studied and then supported by computers, which can in turn affect the nature of the original task and cause it to evolve. To illustrate, word processing has made it easy to manipulate paragraphs and reorder documents, allowing writers a completely new freedom that has affected writing styles. No longer is it vital to plan and construct text in an ordered fashion, since free-flowing prose can easily be restructured at a later date. This evolution of task in turn affects the design of the ideal system. However, we see this evolution as providing a motivating force behind the system development cycle, rather than a refutation of the whole idea of supportive design. This word ‘task’ or the focus on accomplishing ‘work’ is also problematic when we think of areas such as domestic appliances, consumer electronics and e-commerce. There are three ‘use’ words that must all be true for a product to be successful; it must be: useful – accomplish what is required: play music, cook dinner, format a document; usable – do it easily and naturally, without danger of error, etc.; used – make people want to use it, be attractive, engaging, fun, etc.
- 37. 6 Introduction The last of these has not been a major factor until recently in HCI, but issues of motivation, enjoyment and experience are increasingly important. We are certainly even further from having a unified theory of experience than of task. The question of whether HCI, or more importantly the design of interactive sys- tems and the user interface in particular, is a science or a craft discipline is an inter- esting one. Does it involve artistic skill and fortuitous insight or reasoned methodical science? Here we can draw an analogy with architecture. The most impressive struc- tures, the most beautiful buildings, the innovative and imaginative creations that provide aesthetic pleasure, all require inventive inspiration in design and a sense of artistry, and in this sense the discipline is a craft. However, these structures also have to be able to stand up to fulfill their purpose successfully, and to be able to do this the architect has to use science. So it is for HCI: beautiful and/or novel interfaces are artistically pleasing and capable of fulfilling the tasks required – a marriage of art and science into a successful whole. We want to reuse lessons learned from the past about how to achieve good results and avoid bad ones. For this we require both craft and science. Innovative ideas lead to more usable systems, but in order to maximize the potential benefit from the ideas, we need to understand not only that they work, but how and why they work. This scientific rationalization allows us to reuse related con- cepts in similar situations, in much the same way that architects can produce a bridge and know that it will stand, since it is based upon tried and tested principles. The craft–science tension becomes even more difficult when we consider novel systems. Their increasing complexity means that our personal ideas of good and bad are no longer enough; for a complex system to be well designed we need to rely on something more than simply our intuition. Designers may be able to think about how one user would want to act, but how about groups? And what about new media? Our ideas of how best to share workloads or present video information are open to debate and question even in non-computing situations, and the incorporation of one version of good design into a computer system is quite likely to be unlike anyone else’s version. Different people work in different ways, whilst different media color the nature of the interaction; both can dramatically change the very nature of the original task. In order to assist designers, it is unrealistic to assume that they can rely on artistic skill and perfect insight to develop usable systems. Instead we have to pro- vide them with an understanding of the concepts involved, a scientific view of the reasons why certain things are successful whilst others are not, and then allow their creative nature to feed off this information: creative flow, underpinned with science; or maybe scientific method, accelerated by artistic insight. The truth is that HCI is required to be both a craft and a science in order to be successful. HCI IN THE CURRICULUM If HCI involves both craft and science then it must, in part at least, be taught. Imagination and skill may be qualities innate in the designer or developed through experience, but the underlying theory must be learned. In the past, when computers
- 38. HCI in the curriculum 7 were used primarily by expert specialists, concentration on the interface was a lux- ury that was often relinquished. Now designers cannot afford to ignore the interface in favour of the functionality of their systems: the two are too closely intertwined. If the interface is poor, the functionality is obscured; if it is well designed, it will allow the system’s functionality to support the user’s task. Increasingly, therefore, computer science educators cannot afford to ignore HCI. We would go as far as to claim that HCI should be integrated into every computer science or software engineering course, either as a recurring feature of other modules or, preferably, as a module itself. It should not be viewed as an ‘optional extra’ (although, of course, more advanced HCI options can complement a basic core course). This view is shared by the ACM SIGCHI curriculum development group, who propose a curriculum for such a core course [9]. The topics included in this book, although developed without reference to this curriculum, cover the main emphases of it, and include enough detail and coverage to support specialized options as well. In courses other than computer science, HCI may well be an option specializing in a particular area, such as cognitive modeling or task analysis. Selected use of the relevant chapters of this book can also support such a course. HCI must be taken seriously by designers and educators if the requirement for additional complexity in the system is to be matched by increased clarity and usabil- ity in the interface. In this book we demonstrate how this can be done in practice. DESIGN FOCUS Quick fixes You should expect to spend both time and money on interface design, just as you would with other parts of a system. So in one sense there are no quick fixes. However, a few simple steps can make a dramatic improvement. Think ‘user’ Probably 90% of the value of any interface design technique is that it forces the designer to remember that someone (and in particular someone else) will use the system under construction. Try it out Of course, many designers will build a system that they find easy and pleasant to use, and they find it incomprehensible that anyone else could have trouble with it. Simply sitting someone down with an early version of an interface (without the designer prompting them at each step!) is enormously valuable. Professional usability laboratories will have video equipment, one-way mirrors and other sophisticated monitors, but a notebook and pencil and a home-video camera will suffice (more about evaluation in Chapter 9). Involve the users Where possible, the eventual users should be involved in the design process. They have vital know- ledge and will soon find flaws. A mechanical syringe was once being developed and a prototype was demonstrated to hospital staff. Happily they quickly noticed the potentially fatal flaw in its interface.
- 39. The doses were entered via a numeric keypad: an accidental keypress and the dose could be out by a factor of 10! The production version had individual increment/decrement buttons for each digit (more about participatory design in Chapter 13). Iterate People are complicated, so you won’t get it right first time. Programming an interface can be a very difficult and time-consuming business. So, the result becomes precious and the builder will want to defend it and minimize changes. Making early prototypes less precious and easier to throw away is crucial. Happily there are now many interface builder tools that aid this process. For example, mock- ups can be quickly constructed using HyperCard on the Apple Macintosh or Visual Basic on the PC. For visual and layout decisions, paper designs and simple models can be used (more about iterative design in Chapter 5). 8 Introduction Figure 0.1 Automatic syringe: setting the dose to 1372. The effect of one key slip before and after user involvement
- 40. P A R T 1 FOUNDATIONS In this part we introduce the fundamental components of an interactive system: the human user, the computer system itself and the nature of the interactive process. We then present a view of the history of interactive systems by look- ing at key interaction paradigms that have been significant. Chapter 1 discusses the psychological and physiological attributes of the user, providing us with a basic overview of the capabilities and limitations that affect our ability to use computer systems. It is only when we have an understand- ing of the user at this level that we can understand what makes for successful designs. Chapter 2 considers the computer in a similar way. Input and output devices are described and explained and the effect that their individual characteristics have on the interaction highlighted. The computational power and memory of the computer is another important component in determining what can be achieved in the interaction, whilst due attention is also paid to paper output since this forms one of the major uses of computers and users’ tasks today. Having approached interaction from both the human and the computer side, we then turn our attention to the dialog between them in Chapter 3, where we look at models of interaction. In Chapter 4 we take a historical perspective on the evolution of interactive systems and how they have increased the usability of computers in general.
- 42. THE HUMAN 1 OVERVIEW n Humans are limited in their capacity to process information. This has important implications for design. n Information is received and responses given via a number of input and output channels: – visual channel – auditory channel – haptic channel – movement. n Information is stored in memory: – sensory memory – short-term (working) memory – long-term memory. n Information is processed and applied: – reasoning – problem solving – skill acquisition – error. n Emotion influences human capabilities. n Users share common capabilities but are individuals with differences, which should not be ignored.
- 43. 12 Chapter 1 n The human INTRODUCTION This chapter is the first of four in which we introduce some of the ‘foundations’ of HCI. We start with the human, the central character in any discussion of interactive systems. The human, the user, is, after all, the one whom computer systems are de- signed to assist. The requirements of the user should therefore be our first priority. In this chapter we will look at areas of human psychology coming under the general banner of cognitive psychology. This may seem a far cry from designing and building interactive computer systems, but it is not. In order to design something for some- one, we need to understand their capabilities and limitations. We need to know if there are things that they will find difficult or, even, impossible. It will also help us to know what people find easy and how we can help them by encouraging these things. We will look at aspects of cognitive psychology which have a bearing on the use of com- puter systems: how humans perceive the world around them, how they store and process information and solve problems, and how they physically manipulate objects. We have already said that we will restrict our study to those things that are relev- ant to HCI. One way to structure this discussion is to think of the user in a way that highlights these aspects. In other words, to think of a simplified model of what is actually going on. Many models have been proposed and it useful to consider one of the most influential in passing, to understand the context of the discussion that is to follow. In 1983, Card, Moran and Newell [56] described the Model Human Processor, which is a simplified view of the human processing involved in interacting with computer systems. The model comprises three subsystems: the perceptual system, handling sensory stimulus from the outside world, the motor system, which controls actions, and the cognitive system, which provides the processing needed to connect the two. Each of these subsystems has its own processor and memory, although obviously the complexity of these varies depending on the complexity of the tasks the subsystem has to perform. The model also includes a number of principles of operation which dictate the behavior of the systems under certain conditions. We will use the analogy of the user as an information processing system, but in our model make the analogy closer to that of a conventional computer system. Information comes in, is stored and processed, and information is passed out. We will therefore discuss three components of this system: input–output, memory and processing. In the human, we are dealing with an intelligent information-processing system, and processing therefore includes problem solving, learning, and, con- sequently, making mistakes. This model is obviously a simplification of the real situation, since memory and processing are required at all levels, as we have seen in the Model Human Processor. However, it is convenient as a way of grasping how information is handled by the human system. The human, unlike the computer, is also influenced by external factors such as the social and organizational environ- ment, and we need to be aware of these influences as well. We will ignore such factors for now and concentrate on the human’s information processing capabilities only. We will return to social and organizational influences in Chapter 3 and, in more detail, in Chapter 13. 1.1
- 44. 1.2 Input–output channels 13 In this chapter, we will first look at the human’s input–output channels, the senses and responders or effectors. This will involve some low-level processing. Secondly, we will consider human memory and how it works. We will then think about how humans perform complex problem solving, how they learn and acquire skills, and why they make mistakes. Finally, we will discuss how these things can help us in the design of computer systems. INPUT–OUTPUT CHANNELS A person’s interaction with the outside world occurs through information being received and sent: input and output. In an interaction with a computer the user receives information that is output by the computer, and responds by providing input to the computer – the user’s output becomes the computer’s input and vice versa. Consequently the use of the terms input and output may lead to confusion so we shall blur the distinction somewhat and concentrate on the channels involved. This blurring is appropriate since, although a particular channel may have a primary role as input or output in the interaction, it is more than likely that it is also used in the other role. For example, sight may be used primarily in receiving information from the computer, but it can also be used to provide information to the computer, for example by fixating on a particular screen point when using an eyegaze system. Input in the human occurs mainly through the senses and output through the motor control of the effectors. There are five major senses: sight, hearing, touch, taste and smell. Of these, the first three are the most important to HCI. Taste and smell do not currently play a significant role in HCI, and it is not clear whether they could be exploited at all in general computer systems, although they could have a role to play in more specialized systems (smells to give warning of malfunction, for example) or in augmented reality systems. However, vision, hearing and touch are central. Similarly there are a number of effectors, including the limbs, fingers, eyes, head and vocal system. In the interaction with the computer, the fingers play the primary role, through typing or mouse control, with some use of voice, and eye, head and body position. Imagine using a personal computer (PC) with a mouse and a keyboard. The appli- cation you are using has a graphical interface, with menus, icons and windows. In your interaction with this system you receive information primarily by sight, from what appears on the screen. However, you may also receive information by ear: for example, the computer may ‘beep’ at you if you make a mistake or to draw attention to something, or there may be a voice commentary in a multimedia presentation. Touch plays a part too in that you will feel the keys moving (also hearing the ‘click’) or the orientation of the mouse, which provides vital feedback about what you have done. You yourself send information to the computer using your hands, either by hitting keys or moving the mouse. Sight and hearing do not play a direct role in sending information in this example, although they may be used to receive 1.2
- 45. 14 Chapter 1 n The human information from a third source (for example, a book, or the words of another per- son) which is then transmitted to the computer. In this section we will look at the main elements of such an interaction, first con- sidering the role and limitations of the three primary senses and going on to consider motor control. 1.2.1 Vision Human vision is a highly complex activity with a range of physical and perceptual limitations, yet it is the primary source of information for the average person. We can roughly divide visual perception into two stages: the physical reception of the stimulus from the outside world, and the processing and interpretation of that stimulus. On the one hand the physical properties of the eye and the visual system mean that there are certain things that cannot be seen by the human; on the other the interpretative capabilities of visual processing allow images to be constructed from incomplete information. We need to understand both stages as both influence what can and cannot be perceived visually by a human being, which in turn directly affects the way that we design computer systems. We will begin by looking at the eye as a physical receptor, and then go on to consider the processing involved in basic vision. The human eye Vision begins with light. The eye is a mechanism for receiving light and transform- ing it into electrical energy. Light is reflected from objects in the world and their image is focussed upside down on the back of the eye. The receptors in the eye transform it into electrical signals which are passed to the brain. The eye has a number of important components (see Figure 1.1) which we will look at in more detail. The cornea and lens at the front of the eye focus the light into a sharp image on the back of the eye, the retina. The retina is light sensitive and con- tains two types of photoreceptor: rods and cones. Rods are highly sensitive to light and therefore allow us to see under a low level of illumination. However, they are unable to resolve fine detail and are subject to light saturation. This is the reason for the temporary blindness we get when moving from a darkened room into sunlight: the rods have been active and are saturated by the sudden light. The cones do not operate either as they are suppressed by the rods. We are therefore temporarily unable to see at all. There are approximately 120 million rods per eye which are mainly situated towards the edges of the retina. Rods there- fore dominate peripheral vision. Cones are the second type of receptor in the eye. They are less sensitive to light than the rods and can therefore tolerate more light. There are three types of cone, each sensitive to a different wavelength of light. This allows color vision. The eye has approximately 6 million cones, mainly concentrated on the fovea, a small area of the retina on which images are fixated.
- 46. 1.2 Input–output channels 15 Although the retina is mainly covered with photoreceptors there is one blind spot where the optic nerve enters the eye. The blind spot has no rods or cones, yet our visual system compensates for this so that in normal circumstances we are unaware of it. The retina also has specialized nerve cells called ganglion cells. There are two types: X-cells, which are concentrated in the fovea and are responsible for the early detec- tion of pattern; and Y-cells which are more widely distributed in the retina and are responsible for the early detection of movement. The distribution of these cells means that, while we may not be able to detect changes in pattern in peripheral vision, we can perceive movement. Visual perception Understanding the basic construction of the eye goes some way to explaining the physical mechanisms of vision but visual perception is more than this. The informa- tion received by the visual apparatus must be filtered and passed to processing ele- ments which allow us to recognize coherent scenes, disambiguate relative distances and differentiate color. We will consider some of the capabilities and limitations of visual processing later, but first we will look a little more closely at how we perceive size and depth, brightness and color, each of which is crucial to the design of effective visual interfaces. Figure 1.1 The human eye
- 47. 16 Chapter 1 n The human Perceiving size and depth Imagine you are standing on a hilltop. Beside you on the summit you can see rocks, sheep and a small tree. On the hillside is a farmhouse with outbuildings and farm vehicles. Someone is on the track, walking toward the summit. Below in the valley is a small market town. Even in describing such a scene the notions of size and distance predominate. Our visual system is easily able to interpret the images which it receives to take account of these things. We can identify similar objects regardless of the fact that they appear to us to be of vastly different sizes. In fact, we can use this information to judge distances. So how does the eye perceive size, depth and relative distances? To understand this we must consider how the image appears on the retina. As we noted in the previous section, reflected light from the object forms an upside-down image on the retina. The size of that image is specified as a visual angle. Figure 1.2 illustrates how the visual angle is calculated. If we were to draw a line from the top of the object to a central point on the front of the eye and a second line from the bottom of the object to the same point, the visual angle of the object is the angle between these two lines. Visual angle is affected by both the size of the object and its distance from the eye. Therefore if two objects are at the same distance, the larger one will have the larger visual angle. Similarly, if two objects of the same size are placed at different distances from the eye, the DESIGN FOCUS Getting noticed The extensive knowledge about the human visual system can be brought to bear in practical design. For example, our ability to read or distinguish falls off inversely as the distance from our point of focus increases. This is due to the fact that the cones are packed more densely towards the center of our visual field. You can see this in the following image. Fixate on the dot in the center. The letters on the left should all be equally readable, those on the right all equally harder. This loss of discrimination sets limits on the amount that can be seen or read without moving one’s eyes. A user concentrating on the middle of the screen cannot be expected to read help text on the bottom line. However, although our ability to discriminate static text diminishes, the rods, which are concentrated more in the outer parts of our visual field, are very sensitive to changes; hence we see movement well at the edge of our vision. So if you want a user to see an error message at the bottom of the screen it had better be flashing! On the other hand clever moving icons, however impressive they are, will be distracting even when the user is not looking directly at them.
- 48. 1.2 Input–output channels 17 furthest one will have the smaller visual angle. The visual angle indicates how much of the field of view is taken by the object. The visual angle measurement is given in either degrees or minutes of arc, where 1 degree is equivalent to 60 minutes of arc, and 1 minute of arc to 60 seconds of arc. So how does an object’s visual angle affect our perception of its size? First, if the visual angle of an object is too small we will be unable to perceive it at all. Visual acuity is the ability of a person to perceive fine detail. A number of measurements have been established to test visual acuity, most of which are included in standard eye tests. For example, a person with normal vision can detect a single line if it has a visual angle of 0.5 seconds of arc. Spaces between lines can be detected at 30 seconds to 1 minute of visual arc. These represent the limits of human visual acuity. Assuming that we can perceive the object, does its visual angle affect our per- ception of its size? Given that the visual angle of an object is reduced as it gets further away, we might expect that we would perceive the object as smaller. In fact, our perception of an object’s size remains constant even if its visual angle changes. So a person’s height is perceived as constant even if they move further from you. This is the law of size constancy, and it indicates that our perception of size relies on factors other than the visual angle. One of these factors is our perception of depth. If we return to the hilltop scene there are a number of cues which we can use to determine the relative positions and distances of the objects which we see. If objects overlap, the object which is partially covered is perceived to be in the background, and therefore further away. Similarly, the size and height of the object in our field of view provides a cue to its distance. Figure 1.2 Visual angle
- 49. 18 Chapter 1 n The human A third cue is familiarity: if we expect an object to be of a certain size then we can judge its distance accordingly. This has been exploited for humour in advertising: one advertisement for beer shows a man walking away from a bottle in the fore- ground. As he walks, he bumps into the bottle, which is in fact a giant one in the background! Perceiving brightness A second aspect of visual perception is the perception of brightness. Brightness is in fact a subjective reaction to levels of light. It is affected by luminance which is the amount of light emitted by an object. The luminance of an object is dependent on the amount of light falling on the object’s surface and its reflective properties. Luminance is a physical characteristic and can be measured using a photometer. Contrast is related to luminance: it is a function of the luminance of an object and the luminance of its background. Although brightness is a subjective response, it can be described in terms of the amount of luminance that gives a just noticeable difference in brightness. However, the visual system itself also compensates for changes in brightness. In dim lighting, the rods predominate vision. Since there are fewer rods on the fovea, objects in low lighting can be seen less easily when fixated upon, and are more visible in peripheral vision. In normal lighting, the cones take over. Visual acuity increases with increased luminance. This may be an argument for using high display luminance. However, as luminance increases, flicker also increases. The eye will perceive a light switched on and off rapidly as constantly on. But if the speed of switching is less than 50 Hz then the light is perceived to flicker. In high luminance flicker can be perceived at over 50 Hz. Flicker is also more noticeable in peripheral vision. This means that the larger the display (and consequently the more peripheral vision that it occupies), the more it will appear to flicker. Perceiving color A third factor that we need to consider is perception of color. Color is usually regarded as being made up of three components: hue, intensity and saturation. Hue is determined by the spectral wavelength of the light. Blues have short wavelengths, greens medium and reds long. Approximately 150 different hues can be discriminated by the average person. Intensity is the brightness of the color, and saturation is the amount of whiteness in the color. By varying these two, we can perceive in the region of 7 million different colors. However, the number of colors that can be identified by an individual without training is far fewer (in the region of 10). The eye perceives color because the cones are sensitive to light of different wave- lengths. There are three different types of cone, each sensitive to a different color (blue, green and red). Color vision is best in the fovea, and worst at the periphery where rods predominate. It should also be noted that only 3–4% of the fovea is occupied by cones which are sensitive to blue light, making blue acuity lower. Finally, we should remember that around 8% of males and 1% of females suffer from color blindness, most commonly being unable to discriminate between red and green.
- 50. 1.2 Input–output channels 19 The capabilities and limitations of visual processing In considering the way in which we perceive images we have already encountered some of the capabilities and limitations of the human visual processing system. However, we have concentrated largely on low-level perception. Visual processing involves the transformation and interpretation of a complete image, from the light that is thrown onto the retina. As we have already noted, our expectations affect the way an image is perceived. For example, if we know that an object is a particular size, we will perceive it as that size no matter how far it is from us. Visual processing compensates for the movement of the image on the retina which occurs as we move around and as the object which we see moves. Although the retinal image is moving, the image that we perceive is stable. Similarly, color and brightness of objects are perceived as constant, in spite of changes in luminance. This ability to interpret and exploit our expectations can be used to resolve ambi- guity. For example, consider the image shown in Figure 1.3. What do you perceive? Now consider Figure 1.4 and Figure 1.5. The context in which the object appears Figure 1.3 An ambiguous shape? Figure 1.4 ABC
- 51. 20 Chapter 1 n The human allows our expectations to clearly disambiguate the interpretation of the object, as either a B or a 13. However, it can also create optical illusions. For example, consider Figure 1.6. Which line is longer? Most people when presented with this will say that the top line is longer than the bottom. In fact, the two lines are the same length. This may be due to a false application of the law of size constancy: the top line appears like a con- cave edge, the bottom like a convex edge. The former therefore seems further away than the latter and is therefore scaled to appear larger. A similar illusion is the Ponzo illusion (Figure 1.7). Here the top line appears longer, owing to the distance effect, although both lines are the same length. These illusions demonstrate that our per- ception of size is not completely reliable. Another illusion created by our expectations compensating an image is the proof- reading illusion. Read the text in Figure 1.8 quickly. What does it say? Most people reading this rapidly will read it correctly, although closer inspection shows that the word ‘the’ is repeated in the second and third line. These are just a few examples of how the visual system compensates, and some- times overcompensates, to allow us to perceive the world around us. Figure 1.5 12 13 14 Figure 1.6 The Muller–Lyer illusion – which line is longer?
- 52. 1.2 Input–output channels 21 Figure 1.7 The Ponzo illusion – are these the same size? Figure 1.8 Is this text correct?
- 53. 22 Chapter 1 n The human Reading So far we have concentrated on the perception of images in general. However, the perception and processing of text is a special case that is important to interface design, which invariably requires some textual display. We will therefore end this section by looking at reading. There are several stages in the reading process. First, the visual pattern of the word on the page is perceived. It is then decoded with reference to an internal representation of language. The final stages of lan- guage processing include syntactic and semantic analysis and operate on phrases or sentences. We are most concerned with the first two stages of this process and how they influence interface design. During reading, the eye makes jerky movements called saccades followed by fixations. Perception occurs during the fixation periods, which account for approximately 94% of the time elapsed. The eye moves backwards over the text as well as forwards, in what are known as regressions. If the text is complex there will be more regressions. Adults read approximately 250 words a minute. It is unlikely that words are scanned serially, character by character, since experiments have shown that words can be recognized as quickly as single characters. Instead, familiar words are recognized using word shape. This means that removing the word shape clues (for example, by capitalizing words) is detrimental to reading speed and accuracy. The speed at which text can be read is a measure of its legibility. Experiments have shown that standard font sizes of 9 to 12 points are equally legible, given pro- portional spacing between lines [346]. Similarly line lengths of between 2.3 and 5.2 inches (58 and 132 mm) are equally legible. However, there is evidence that reading from a computer screen is slower than from a book [244]. This is thought to be due to a number of factors including a longer line length, fewer words to a page, DESIGN FOCUS Where’s the middle? Optical illusions highlight the differences between the way things are and the way we perceive them – and in interface design we need to be aware that we will not always perceive things exactly as they are. The way that objects are composed together will affect the way we perceive them, and we do not per- ceive geometric shapes exactly as they are drawn. For example, we tend to magnify horizontal lines and reduce vertical. So a square needs to be slightly increased in height to appear square and lines will appear thicker if horizontal rather than vertical. Optical illusions also affect page symmetry. We tend to see the center of a page as being a little above the actual center – so if a page is arranged symmetrically around the actual center, we will see it as too low down. In graphic design this is known as the optical center – and bottom page margins tend to be increased by 50% to compensate.
- 54. 1.2 Input–output channels 23 orientation and the familiarity of the medium of the page. These factors can of course be reduced by careful design of textual interfaces. A final word about the use of contrast in visual display: a negative contrast (dark characters on a light screen) provides higher luminance and, therefore, increased acuity, than a positive contrast. This will in turn increase legibility. However, it will also be more prone to flicker. Experimental evidence suggests that in practice negat- ive contrast displays are preferred and result in more accurate performance [30]. 1.2.2 Hearing The sense of hearing is often considered secondary to sight, but we tend to under- estimate the amount of information that we receive through our ears. Close your eyes for a moment and listen. What sounds can you hear? Where are they coming from? What is making them? As I sit at my desk I can hear cars passing on the road outside, machinery working on a site nearby, the drone of a plane overhead and bird song. But I can also tell where the sounds are coming from, and estimate how far away they are. So from the sounds I hear I can tell that a car is passing on a particular road near my house, and which direction it is traveling in. I know that building work is in progress in a particular location, and that a certain type of bird is perched in the tree in my garden. The auditory system can convey a lot of information about our environment. But how does it work? The human ear Just as vision begins with light, hearing begins with vibrations in the air or sound waves. The ear receives these vibrations and transmits them, through various stages, to the auditory nerves. The ear comprises three sections, commonly known as the outer ear, middle ear and inner ear. The outer ear is the visible part of the ear. It has two parts: the pinna, which is the structure that is attached to the sides of the head, and the auditory canal, along which sound waves are passed to the middle ear. The outer ear serves two purposes. First, it protects the sensitive middle ear from damage. The auditory canal contains wax which prevents dust, dirt and over-inquisitive insects reaching the middle ear. It also maintains the middle ear at a constant temperature. Secondly, the pinna and auditory canal serve to amplify some sounds. The middle ear is a small cavity connected to the outer ear by the tympanic membrane, or ear drum, and to the inner ear by the cochlea. Within the cavity are the ossicles, the smallest bones in the body. Sound waves pass along the auditory canal and vibrate the ear drum which in turn vibrates the ossicles, which transmit the vibrations to the cochlea, and so into the inner ear. This ‘relay’ is required because, unlike the air-filled outer and middle ears, the inner ear is filled with a denser cochlean liquid. If passed directly from the air to the liquid, the transmission of the sound waves would be poor. By transmitting them via the ossicles the sound waves are concentrated and amplified.
- 55. Exploring the Variety of Random Documents with Different Content
- 56. Minerva is a very nice hen and it is so nice she has so many children at once. I so do like to pick out names for children. Now I have thinks there is needs for me to hurry to get those christening robes done for her children, being as they are hatching now. On the day of their christening I will carry them in a little basket to the cathedral. There is needs to carry little chickens in a basket, for they are delicate. To-day I did show Minerva the little cap with ruffles on it that I have just made for her to wear to the cathedral at their christening. I made it like Jenny Strong’s morning-cap with ruffles on it. After I did talk some more with Minerva, and she did chuckle some more chuckles, I did make a start to go to the cathedral to have a thank service for the borning of Sanzio Raphael in 1483. As I did go, I went aside to the pig-pen. Every time my way goes near to the way that goes to the pig-pen I do go that way. I so go to take a peep at Aphrodite. She does have such a motherly look with those dear baby-pigs about her. How nice it must be to be a mother-pig. It must be a big amount of satisfaction, having so many babies at one time.
- 57. CHAPTER XXII How Solomon Grundy Falls Sick and Grows Well again; and Minerva’s Chickens are Christened; and the Pensée Girl, with the Far-Away Look in her Eyes, Finds Thirty-and-Three Bunches of Flowers. To-day I went not to school. For a long time after breakfast the mamma did have me to cut potatoes into pieces. To-night and to- morrow night the grown-ups will plant the pieces of potatoes I cut to-day. Then by-and-by—after some long time—the pieces of potato with eyes on them will have baby potatoes under the ground. Up above the ground they will be growing leaves and flowers. One must leave an eye on every piece of potato one plants in the ground to grow. It won’t grow if you don’t. It can’t see how to grow without its eye. All day to-day I did be careful to leave an eye on every piece. And I did have meditations about what things the eyes of potatoes do see there in the ground. I have thinks they do have seeing of black velvet moles and large earthworms that do get short in a quick way. And potato flowers above the ground do see the doings of the field—and maybe they do look away and see the willows that grow by the singing creek. I do wonder if potato plants do have longings to dabble their toes. I have supposes they do just like I do. Being a potato must be interest—specially the having so many eyes. I have longings for more eyes. There is much to see in this world all about. Every day I do see beautiful things everywhere I do go.
- 58. To-day it was near eventime—the time I did have all those potatoes ready for plants. Then I did go to see Solomon Grundy in the pig-pen. I did take a sugar-lump in my apron pocket for his dear mother, Aphrodite. She had appreciations and well looks. But the looks of Solomon Grundy—they were not well looks. He did lay so still in a quiet way. I gave to him three looks. I felt a lump come in my throat. His looks they were so different. I made a run for the wood-box—the wood-box I did bring before for the getting-in of Brave Horatius to service in the pig-pen. I did step on it in getting Solomon Grundy out of the pig-pen. I did have fears if I did it in jumps, as I always do, the jumps might bother the feelings of Solomon Grundy. So I did have needs for that box. It is such a help. Every time I do get a place fixed in the pig-pen so some of the pigs can get out to go to walks and to go to the cathedral service, the grown-ups at the ranch-house do always fix the boards back again. So a box is helps to get the little pigs that are n’t too big over the top. When I did have Solomon Grundy over the top, I did cuddle him up in my gray calico apron. I have thinks he does like the blue one best. But to-day he had not seeings it was n’t the blue one I had on. He did not give his baby squeaks. He was only stillness. I did have fears that sickness was upon him. He has lost that piece of asfiditee I did tie around his neck the other day. That was the last piece I did have. It was the little piece that was left of the big piece that the mamma did tie around my neck, and I did make divides with my friends. But Solomon Grundy—he has lost his share both times. He does lose it in a quick way. And I did have no Castoria to give him, because the mamma has gone and put away the baby’s bottle of Castoria where I cannot find it.
- 59. I did not have knowings what to do for him. But I did have thinks the man that wears gray neckties and is kind to mice would have knowings what to do for the sickness of Solomon Grundy. I made starts to the mill by the far woods. Brave Horatius was waiting at the barn. He gave his tail two wags and followed after. We went by Michael Angelo Sanzio Raphael. I did tell him the baby in my arms was sick. I said a little prayer over his head. We went along the lane. When we were come to Good King Edward I and lovely Queen Eleanor, we made stops. I did tell them of the sickness of the baby. I said a little prayer for his getting well. And I did hold him up for their blessing. Then we went on, and Brave Horatius came a- following after. When we were come to the ending of the lane, I said another little prayer. Then we went on. When we were come near unto the altar of Good King Edward I, I said another little prayer. Then we went on. Elizabeth Barrett Browning was in the woods, and she went with us. She mostly does so. And we went on. By-and-by my arms was getting tired. Solomon Grundy, now that he is older grown, does get a little heavy when I carry him quite a long ways. When I was come to the far end of the near woods, I met the man that wears gray neckties and is kind to mice. He smiled the gentle smile he always does smile, and he took Solomon Grundy into his arms. I have thinks he did see the tiredness that was in my arms. When he sat down on a log with the dear pig, I said I had fears Solomon Grundy was sick. He said he did too. But he smoothed my curls back and he said, “Don’t you worry; he will get well.” Hearing him say that made me have better feels. Men are such a comfort—men that wear gray neckties and are kind to mice. One I know. He looks kind looks upon the forest and he does love the grand fir trees that do grow there. I have seen him stretch out his arms to them just like I do do in the cathedral. He
- 60. does have kindness for the little folks that do live about the grand trees. His ways are ways of gentleness. All my friends have likes for him, and so had Solomon Grundy. To-day he said he would take Solomon Grundy back to camp by the mill to his bunk-house. A warming he did need, so he said, and he said he would wrap him in his blanket and take care of him until morningtime was come. Then he did go the way that goes to the far woods and I did go the way that does go to the cathedral. I so went to have a little thank service for the getting well of Solomon Grundy. I do have knowings he will be well when morningtime is come. With me to the cathedral did go Elizabeth Barrett Browning and Brave Horatius. This morning before breakfast I did go to the cathedral to say thanks for the goodness of one William Wordsworth, for this is the day of his borning in 1770. With me did go Thomas Chatterton Jupiter Zeus. And Brave Horatius came a-following after. After the morning’s work was done, I took my little basket most full of christening robes to the pen-place near the hen-house where is Minerva and her fourteen baby chickens. One baby chicken did n’t hatch. I had most enough christening robes ready on yesterday afternoon but one. When I did go to sing her baby to sleeps, Elsie did help me to fix that one while I did carry in some wood for her. She put a little ruffle of lace on it and a little blue bow of ribbon. It looked very nice. I did have thinks how nice they would look if all of the christening robes for the baby chickens of Minerva did have little bows of ribbon on them. Elsie had asks what was my thoughts about, and I did tell her. And she did say she had thinks that way too. And she did make a go to her work-basket that was under the shelf where does set the bottle
- 61. of vaseline that her young husband does smooth back his pumpadoor with. That vaseline jar is most empty again. When Elsie did find some little ribbons in her work-basket, she did go and raise up the trunk-lid and she did find some more little ribbons in the tray of the trunk. She tied them all into little bows. And some were pink and some were lavande and some were blue and some were rose. There was enough for every baby chicken to have one on his christening robe. And I did sew them all on at night-time on yesterday when the mamma did put me under the bed. Light enough came from the lamp on the kitchen table so I could have sees to sew them all on. When we was come near unto the cathedral, I made a stop to put on their christening-robes. Nicholas Boileau and Jean Molière did have lavande ribbon bows on theirs. They waited waits in a corner of the basket while I did put on the others. Sir Walter Raleigh had a little pink bow on his. He would not keep still while I was getting him into his robes. He peeped three times. But Sir Francis Bacon was more fidgety than he was. It took quite a time to get his christening robe on. Ben Jonson did wear the christening robe with the ruffle of lace around it, and before I did get him put back in the basket there, he did catch his toe in that ruffle of lace. Then he peeped. I took his toe out of the ruffle, and put a christening robe with a rose ribbon bow on it on Francis Beaumont and one like it on John Fletcher, because their names was together in the book Angel Mother did write in. After I did get little brown Oliver Goldsmith and all the rest of the children of Minerva into their christening robes, then I did take out of my pocket her little white cap with the ruffles on it like the ruffles on the morning-cap of Jenny Strong. I tied it under Minerva’s bill. She was a sweet picture in it coming down the cathedral aisle by my
- 62. side. Minerva is a plump hen of gentle ways. It is not often she does talk, but she did chuckle all of the time while her baby chickens was getting christened. Brave Horatius stood by the altar and Lars Porsena of Clusium did perch upon his back. Lucian Horace Ovid Virgil did sit on a log close by. And Mathilde Plantagenet watched from the pasture-bars. Menander Euripides Theocritus Thucydides did walk by my side when we went goes to have asks for the blessing of Saint Louis on all Minerva’s baby chickens after they were christened. Then I did sing “Hosanna in Excelsis.” And Ben Jonson peeped and so did Francis Beaumont and Pius VII. He was wiggling so that his christening robe was most off him. I put it on again. Then I did stop to straighten up Minerva’s cap with the ruffles on it. It had had a slip-back. Then we had more prayers. Afterward we all did have goes back to the chicken-yard pen. I took off Minerva’s cap so it would be clean for cathedral service on Sundays. Then I put her and all her children back in their pen, after they did have their christening robes off. After I did give Minerva some good-bye pats and advices about bringing up her children, then I did go goes to the house of Sadie McKibben. Menander Euripides Theocritus Thucydides did walk by my side and Brave Horatius came a-following after. When I was come to the house of Sadie McKibben, there was Dear Love. They was glad we was come, and they had likes for Minerva’s little cap with the ruffles around it like the morning-cap of Jenny Strong. Dear Love did give Thomas Chatterton Jupiter Zeus some pats on his nice white paws. And they did talk on. I did have hears of them saying of the pensée girl with the far-away look in her eyes, that is come again to visit her aunt of the gray calico dress with the black bow at its neck. I was glad she is come again. I whispered to Thomas Chatterton
- 63. Jupiter Zeus about my glad feels in his left ear. He cuddled up more close. We listened more listens. Dear Love too did say to Sadie McKibben as how it is the man of the long step that whistles most all of the time has great love for the pensée girl with the far-away look in her eyes; and how it is he is afraid to speak to her about this great love he has for her. And more Dear Love did say of how it is he does pick bunches of flowers in the woods for her and then he does lay them by an old log because he has too shy feels to take them on to her. Thomas Chatterton Jupiter Zeus did stick out his right front foot. I gave it a pat, and I did give him some throat rubs,—that he had likes for,—and all of the time I was having thinks. I looked looks out the side window of the house of Sadie McKibben. A white cloud was sailing in the sky. A little wind was in the woods. It was calling, “Petite Françoise, come, petite Françoise.” I did tell Dear Love and Sadie McKibben there was needs for me to hurry away. They did have understanding, and Sadie McKibben did say it was not long I was staying to-day, and she would wait waits for my return coming on the morrow. Dear Love did tell me of the pieces she did find in the top of her trunk that were waiting waits to be made into christening robes for little folks that now do have their borning-time. I was glad, for there is needs of more. After I did say good-bye, I went goes on to the woods. I did not follow the trail that does go to the moss-box where I do leave letters on leaves for the fairies. The wind was calling. I followed after it. It was not adown the path that does lead to the nursery. It was calling over logs in the way that does lead to where is that old log with the bunches of flowers by it and under its edges. They was the flowers that the man of the long step that whistles most all of the time did gather for the pensée girl with the far-away look in her eyes. Some
- 64. of the bunches of flowers was all faded. It is days a long time since he did put them there, and it is only a little time since he did put the last ones there. I set down on the moss my basket that I did carry Minerva’s baby chickens to christening in. Then I made begins. First I put some moss in the basket, then I did put in some of the bunches of flowers. I put in the most faded ones because they had been waiting waits the longest. Then we all did go in a hurry to the house of her aunt of the gray calico dress with the black bow at its neck. The aunt was not there, and we were glad; but the pensée girl with the far-away look in her eyes was there. She came to the door when we did tap upon its handle. I did tell her all in one breath that we was making begins to bring the flowers that the man of the long step that whistles most all of the time did gather for her on many days. We gave her explanations how it was too shy feels he had to bring them to her himself, so he did lay them by the old log. I told her as how it was we did bring the most faded ones first because they was waiting waits the longest; and she did take them all up in her arms. And I told her my dog’s name was Brave Horatius and he was a fine dog, and that Thomas Chatterton Jupiter Zeus was a most lovely wood-rat, and I held out his white paw for her to have feels of; but he did pull it back and cuddle his nose up close to my curls. I told her how it was he was shy, too, and when he had knows of her better he would let her pat his nice white paws. Then I did take my basket and go goes in a hurry back to get the flowers. I did carry the next most old ones to her. And she was glad for them. She was waiting waits for me on the steps of the house of her aunt of the gray calico dress with the black bow at its neck. She was ready to go back with us to the log where the flowers was; and there was joy-lights in her eyes. While we did go along, I did tell her
- 65. more about the little animal and bird folks that do live in the woods and I did tell her about the great love the man of the long step that whistles most all of the time does have for her. Quietness was upon her, and we did walk on in a slow way. A beetle went across the path and a salal bush did nod itself to us. The wind made little soft whispers, and by-and-by we was come to the log. She did kneel down by it, and she looked looks for a long time at all the bunches of flowers. And I did say a little prayer and Thomas Chatterton Jupiter Zeus did squeak a little squeak. I made counts of the bunches of flowers, and they were thirty-and-three. I saw a chipmunk, and I followed him after to see how many stripes he did have on his back and where was his home; and on the way I saw other birds and I followed them after on tiptoes to have sees where they were having goes to. And in the bushes there was a little nest with four eggs in it with speckles on them. I did have thinks there was needs for me to pick out names for the little birds that will hatch out of those eggs. This is a very busy world to live in. There is much needs for picking out names for things. I am very happy. I have been to the cathedral to pray again that the angels will bring a baby to Dear Love soon.
- 66. CHAPTER XXIII How Opal and Brave Horatius Go on Explores and Visit the Hospital.—How the Mamma Dyes Clothes and Opal Dyes Clementine. My legs do feel some tired this eventime. I’ve been most everywhere to-day. I so have been going to tell the plant-folks and the flower-folks and the birds about this day being the going-away day of one William Shakespeare in 1616. Before yet breakfast-time was come, I did go to the cathedral to say prayers of thanks for all the writings he did write. With me did go Brave Horatius and Lars Porsena of Clusium and Thomas Chatterton Jupiter Zeus and Lucian Horace Ovid Virgil. When we were come again to the house, they did wait waits while I did go to do the morning works. After the morning works were done, I did put pieces of bread and butter in papers in my pockets for all of us. I put some milk in the bottle for Menander Euripides Theocritus Thucydides. He was waiting waits for me by the pasture- bars. He is a most woolly lamb. He was glad for his breakfast and he was glad to have knows about this day. While I was telling them all there what day this is, Plutarch Demosthenes made a little jump onto a little stump. He looked a look about and made a jump-off. Sophocles Diogenes came a-following after. They both did make some more jumps. Their ways are ways of playfulness. They are dear lambs.
- 67. While I was telling them all, Menander Euripides Theocritus Thucydides did in some way get the nipple off his bottle, and the rest of the milk did spill itself out the bottle. I hid the bottle away by a rock. Menander Euripides Theocritus Thucydides did follow me after. He does follow me many wheres I do go to. We went all on. We saw fleurs and I did stop moments to have talks with them. I looked for other fleurs that I had longs to see. Everywhere that we did go I did look looks for teverin and yellow éclaire and pink mahonille and mauve and morgeline. When Brave Horatius had askings in his eyes for what I was looking, I did give to him explanations. He looked looks back at me from his gentle eyes. In his looks he did say, they are not hereabout. We went on. We went to forêt d’Ermenonville and forêt de Chantilly. We went adown Lounette to where it flows into Nonette—and we went on. Everywhere there were little whisperings of earth-voices. They all did say of the writes of William Shakespeare. And there were more talkings. I lay my ear close to the earth where the grasses grew close together. I did listen. The wind made ripples on the grass as it went over. There were voices from out the earth. And the things of their saying were the things of gladness of growing. And there was music. And in the music there was sky-twinkles and earth-tinkles. That was come of the joy of living. I have thinks all the grasses growing there did feel glad feels from the tips of their green arms to their toe roots in the ground. And Brave Horatius and the rest of us did n’t get home until after supper-time. The folks was gone to the house of Elsie. I made a hunt for some supper for Brave Horatius. I found some and I put it in his special dish. Then I came again into the house to get some bread and milk. There was a jar of blackberry jam on the cook-table. It had interest looks. Just when I happened to be having all my
- 68. fingers in the jar of blackberry-jam, there was rumblings of distress come from the back yard. I climbed onto the flour barrel and looked a look out the window. There near unto my chum’s special supper- dish sat the pet crow with top-heavy appears. There was reasons for his forlorn looks, for Brave Horatius had advanced to the rear of Lars Porsena of Clusium and pulled out his tail-feathers. I have had no case like this before. I felt disturbs. I had not knowings what to do for it. I had some bandages and some mentholatum in my pocket. I took Lars Porsena of Clusium—all that was left of him with his tail-feathers gone—and I sat down on the steps. First I took some mentholatum and put it on a piece of bandage. I put the piece of bandage onto Lars Porsena of Clusium where his tail-feathers did come out. Then I did take the long white bandage in the middle, and I did wrap it about Lars Porsena of Clusium from back to front—in under his wings and twice on top, so the bandage would stay in place on the end of him where his tail- feathers came out. Then I did make a start to the hospital. I did have wonders how long the needs would be for Lars Porsena of Clusium to be there before his tail would grow well again. I only did have going a little way when I did meet with the man that wears gray neckties and is kind to mice. He looked a look at me and he looked a look at Lars Porsena of Clusium in my arms. Then he did have askings why was it Lars Porsena was in bandages. I told him explanations all about it. He pondered on the matter. Then he picked me and Lars Porsena up and set us down on a stump. He told me there was no needs for me to have wonders about how long the need would be for Lars Porsena of Clusium to be in the hospital with bandages on him. He did talk on in his gentle way of how it is birds that do lose their tail-feathers do grow them on again. He so said and I did have understanding.
- 69. Then he did take up Lars Porsena of Clusium in his arms. And he unwrapped him from front to back and back to front. When the bandage was all off him, Lars Porsena of Clusium did give himself a stretch and his wings a little shake. And I said a little prayer for his getting well and a new tail soon. And the man that wears gray neckties and is kind to mice said Amen. Then we came home. To-day was dyeing day. The mamma dyed. She dyed clothes—old ones. First she washed them in the tub. Then she put them in the boiler on the stove. In the boiler was beautiful blue water. I know because I climbed on the stove-hearth and peeked in. The mamma did n’t make this water blue with balls like she does the rench water for the clothes on wash-days. She made this water blue with stuff out of an envelope. I had sees of her tear its corner off, and the blue little specks came out of that envelope in a quick way. The specks so did come in a more hurry way when she did give the envelope some shakes. All the clothes the mamma did carry from the wash-tub to the boiler—all those clothes was blue when she took them out; and afterwards the blue was yet with them and they hung upon the line. I see them quiver blue quivers when the wind blows. After she did hang them there on the line, the mamma did leave the boiler of dye-blue water on the stove. And she is gone goes to the house of her mother by the meeting of the roads. She told me to watch the house and let the fire go out. It so is gone a long time ago, and I keep watch. The blue water in the boiler has cold feels now. I stood upon the stove and I put my arm way down in it, and it was coldness. First I did only touch touches on the water with my finger. It was warmness then. That was just when the mamma did go.
- 70. She is hours and hours gone now. I have been keeping watches of the house like she did say for me to do when she went away. And in- between times I have been reading reads in the books Angel Mother and Angel Father did write in. I have been screwtineyesing the spell of words. Now I am going to have dyeing day like the mamma did have on this morning. It is so much of fun to lift things up and down in blue water. On wash-days the mamma has me to do it much. She calls it renching the clothes. When it’s blue water in a boiler, it’s dyeing them. I have been dyeing like the mamma dyed this morning. First I did dye the mamma’s bag of blueing balls. That bag was getting pale looks. Next I did dip in the mamma’s clothes-pin bag. It was brownness before. I have not sure feels yet what color it is going to be since it has had its dye. I took all the clothes-pins out first. Then I did give them all a dip. They did bob about in a funny way. I made whirls in the dye-blue water with my fingers, so the clothes-pins would make some more bobs. It was very nice, standing there on top the cook-stove watching the bobs they made in the boiler. Then I made a start to dye handles. First I dipped in the butcher- knife handle. Then I did give the dipper-handle a dip. I had carefuls to make it go only half-way. Then I did give the handle of the potato-masher a dip. And I gave the hammer-handle a dip in the dye-blue water. Clementine came in a walk up step on the back porch. She looked a look in. She is such a friendly Plymouth Rock hen. She walked right into our house and came in a hop up by the dye-blue water. She so does like my blue calico apron. She hops up on my knee when I sit down to talk to the chickens in the chicken park. I had thinks being as she has likes for my blue calico apron she would have likes for blue feathers; so I did give her a gentle dip in the dye-blue water
- 71. and two more. She walked right out our front door without even a thank chuckle. I never had knows of her to do so before. The dye- blue water was waiting waits. Next I dipped the Plymouth Rock rooster in. He did object to being dyed blue. He was quite fidgety. I had decides not to coax any more folks from the chicken yard to get dyed blue feathers. I looked looks about the house we live in. I had seeing of a box of matches the mamma did leave on a chair in the bedroom. The mamma has said I must n’t touch a box of matches on the cupboard shelf. And I don’t. But she did n’t say I must n’t touch them when she leaves them on a chair. So I have took the box of matches and it has had its dip. It has a limp feel. I have put it on the back steps to get its form again. And all the matches that was in the box have had their dips in the dye-blue water. I have laid them in rows on the grass to have a dry. And now I do have thinks how nice it will be on next time when dyeing day is come if the mamma does have seeing as how I could be helps—being as I now do have so much knowing of the ways of dyeing. I have thinks a big amount of helps I could be. Now while the things I have dyed do dry, I am going goes to the cathedral to have a long service there, for this is the borning day of Saint Louis in 1215. And many wheres there is needs for me to go to tell the plant- folk all about this being the day of his borning. And too it is the borning day of Oliver Cromwell in 1599, and the borning day of Padre Martini in 1706, and it is the going-away day of Torquato Tasso in 1595. The winds sing of these. And the great pine tree is saying a poem about this day.
- 72. CHAPTER XXIV How the Mamma’s Wish Came True, and how Opal was Spanked for it; and of the Likes which Aphrodite Had for a Clean Place to Live in. In the morning of to-day, before I did eat my bowl of mush and milk for breakfast, I did go to the cathedral to say thank prayers for the good works of Leonardo da Vinci, for this is the day of his going away in 1519. When after-breakfast works was done, the mamma did have me to churn. While I did make the handle with the cross sticks on it go up and down in the churn, I did have hearing of the little glad songs all the fleurs were singing out in the field. When the butter was come, the mamma did take it out the churn. She put all the little yellow lumps in a wood bowl. Then she gave to them pats and more pats. When she got through patting the butter into its proper form, the mamma did throw the butter-paddle over on the cook-table. She said she hoped and wished that she would never see that butter-paddle again. She won’t. After I heard her say that, I floated it away in the creek. It made a nice boat. It did sail along in a bobby way. I took Solomon Grundy with me. I just let him dabble his toes. When he is an older pig, he can wade right out into the creek with me. His eyes did look bright to-day while I was telling him what we was going to do when he got to be a bigger pig. When I was come back to the house we live in, the mamma did spank me. Then she did send me to get that butter-paddle in a
- 73. hurry. It was making bobs by the reeds by the old rail fence where the singing creek goes under and on. I brought it back to her and then she did take and spank me again. Now I have wonders about things—the mamma did say she wished she would never see it again. After I did mind the baby and sleeps was come upon it, then I did walk into the garden. I went there to find out how much things had grown since last time I was there. First I pulled up a bean plant. It looked a little more big—the two peek-a-boo leaves did. After I looked close looks at it, I did plant it again. Then I pulled up a radish. It was doing nicely and I ate it. I forgot to give it close looks before I put it in my mouth to see how much it did grow since that last time. After I swallowed it, I pulled up another radish to find out. It was doing well. I put it back in the garden again and I went to the house and got it a drink of buttermilk. I carried it out to it in the papa’s shaving-mug. There was more drink than one radish needs, so I did give four onions and two more radishes sips of buttermilk. And I did give to the papa’s shaving-mug some washes in the brook, and I put it back in its place on the shelf again. Just then the mamma had comes into the house. And there was more spanks. The back part of me does feel sore feels. I have thinks I will go and give geology lectures to the folks in the nursery, and too I will sing them lullaby songs and the bird and fleur chant de fête de grandpère of niverolle and ortolan and verdier and étourneau and nenufar and éclaire and ulmaire and fraxinelle.
- 74. A PATH TO “EXPLORES” IN THE FAR WOODS I so have gone goes, and the folks in the nursery was glad for food and songs. And afterwards I went more on into the woods. There was little whispers among the leaves. And there was a song in
- 75. the tall fir tree-tops. And a pine tree was saying a poem. I listened listens. Then I went goes on. I saw a man coming. He did take long steps. When he was nearer come, I had seeing it was the man that wears gray neckties and is kind to mice. I did go adown the path in a more quick way. He did have seeing of my coming. Then I did hide behind a tree. He came on. When he was near the tree he did say, “I thought I saw someone coming. Guess I was mistaken. I think I’ll take these splints for the hospital back to the mill.” When I did hear him say that, I ran in a quick way back to the path. He did n’t see me. He was looking long looks away. Then I did give his coat-sleeve a gentle pull, and he did whistle, and he did ask me if there was needs for splints at the hospital. And I told him all in one breath how much needs there was. He had me to tell him all over again about the little chicken that did have its leg hurt. And I gave him explanations how it was Sir Francis Bacon did have his leg hurt in a real bad way, and the big folks was going to kill him, but they gave him to me for my very own because he was n’t any good any more. And the man that wears gray neckties and is kind to mice did have understanding, and he went goes with me to the hospital that I do have for little hurt folks, at Saint-Germain-en-Laye. While I did hold little Sir Francis Bacon, the man that wears gray neckties and is kind to mice did fix the splints on his hurt leg in a gentle way. Then I did pray prayers for his getting well soon. Brave Horatius did bark Amen —and one of the most tall pine trees was saying a poem. After morning’s works was done I was washing out clothes for the baby. I thought what a nice christening robe one of the baby’s dresses would make for one of the new baby pigs. The mamma had
- 76. not thoughts that way. When the dress was on the line, I did go by the chicken-yard to have sees how the children of Minerva are growing. Pius VII is getting some tail-feathers. He comes to feed from my hand every day, and he likes to go to school in my little basket. He has not been for a whole week now, because the last time I took him he peeped and teacher sent us home. Next day I took Francis Beaumont and John Fletcher, and they was quiet. Last time I took them to cathedral service, Ben Jonson pecked Sir Walter Raleigh on the head. I said prayers over them for peace between them. Then I put one in a little box on one log and I put the other one in a little box on the other log. The boxes was alike. To-day I had sees of these two drinking out of the water-pan together. Peace was between them. She is a nice mother-hen that has got all her children growed up. And little Edmund Spenser was scratching for a worm near his little brown brother Oliver Goldsmith. And all Minerva’s family was growing well. I felt satisfaction feels about it, and I sat down on a log to pick out names for the twins I am going to have when I grow up. I picked out a goodly number of names, but I could not have decides which ones. I had thinks I would wait a little time, and I had remembers it was time for me to be making another portrait of Solomon Grundy. So I went around by the pig-pen to get Solomon Grundy. I said comfort words to Aphrodite. I told her how it was I was just taking Solomon Grundy to make a portrait of him, and as how I was going to make it in the same way and in the same place as I did make her portrait quite a time ago. She grunted a short grunt and then a long grunt. Sometimes it is difficult to understand pig talk. But her next grunt—it was very plain. It was just an invitation to make Solomon Grundy’s portrait there by her side, and no needs of taking him out of the pig-pen.
- 77. I told her yes, I would make his portrait right there by her, and I did bring many brown bracken ferns after I did have the pig-pen cleaned out. Most every day I do give the pig-pen a rake-out, and bring some clean dirt from the garden. I have thinks pigs do have likes for clean places to live in. It brings more inspirations to their souls. And, too, every day Aphrodite does have likes for her feeding- trough to be scrubbed clean all over. And I have planted ferns and fleurs all around her pig-pen. It is a very nice place, with sweet smells of grass and fleurs. And Aphrodite was glad for the brushing I did give her to-day. I’ve got a brush—a nice new brush—a good new brush. It is for to brush my pig friends. They so do need brushings. This new brush the man that wears gray neckties and is kind to mice did get for me last time he did go to the mill town. The pigs do like the feels the new brush does make upon their backs. The clean feels it does give to them are pleasant to their souls. After I did give her the brushing, I did get moss and cover the clean feed-trough with it. That made a nice place to sit and draw Solomon Grundy’s portrait by his mother there. I drew him lying by her side. Then I had him to stand on his feet, and I drew one of him that way. I had it almost done. There was a little noise. It was the step of someone going by. I had not knows who it was. I went on drawing Solomon Grundy’s ears and his curly tail. Then I had knows what it was. It was that chore boy come to feed the pigs—and he poured all that bucket of swill on top the moss and Solomon Grundy’s portrait and me. The feels I did feel—they was drippy ones. And I did have decides to make that other portrait of Solomon Grundy another time. I said good-bye to Aphrodite. Then I went goes in a quick way to the singing creek where the willows grow, to get the swill-smells off.
- 78. First I did wade out a little way. Then I sat down. The water came in a nice way up to my neck, and it went singing on. I gave my curls wash-offs, and I did listen to the song the creek was singing as it did go by. It was a song of the hills. Being up to my neck made the water sounds very near to my ears. I had likes for that. By-and-by I did have feels that I was clean again and I did have thinks I better go get some dry clothes on, because sitting there in the singing creek did make my clothes some wet. When I was come to the house we live in, the mamma was gone to the house of Elsie, so I did go in. First I did give my clothes some wring-outs by the steps, so the water would not have drips on the kitchen floor, for the mamma has likes to keep her house very clean. When I did have dry clothes on me, I did go to hang the wet ones on bushes in the woods to dry. Thomas Chatterton Jupiter Zeus went with me. Lucian Horace Ovid Virgil rode in one of my apron pockets and Felix Mendelssohn rode in the other one. And Louis II, le Grand Condé, did have rides in my sleeve. We was all very glad. As we went along, I had seeings the strings I have put on the bushes for the birds was gone. We went on and on some more. I did have looks about. I did have seeing of little wood-folks going their ways. I watched their little moves and I had seeing of what color they was. I made stops to tell them about this being the borning day of Linnæus in 1707, and the going-away day of Georges Cuvier in 1832. We went on. All things was glad. The winds did sing. The leaves did sing. The grasses talked in whispers all along the way. I have thinks they were saying, “Petite Françoise, l’été approche—l’été approche.” I did have hearings to all they were so saying, as I did go along. And the little birdlings in their cradles were calling for more to eat. And I did make a stop to watch the mother-birds and father- birds in their comings and goings. Now are busy times.
- 80. Welcome to our website – the perfect destination for book lovers and knowledge seekers. We believe that every book holds a new world, offering opportunities for learning, discovery, and personal growth. That’s why we are dedicated to bringing you a diverse collection of books, ranging from classic literature and specialized publications to self-development guides and children's books. More than just a book-buying platform, we strive to be a bridge connecting you with timeless cultural and intellectual values. With an elegant, user-friendly interface and a smart search system, you can quickly find the books that best suit your interests. Additionally, our special promotions and home delivery services help you save time and fully enjoy the joy of reading. Join us on a journey of knowledge exploration, passion nurturing, and personal growth every day! ebookbell.com