HCI 1st and 2nd sessions
- 1. Human Computer Interaction ICT 2402
- 2. What is HCI? HCI is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major trends surrounding them. (The Association for Computing Machinery). is the study of interaction between people (users) and computers. often regarded as the intersection of computer science, behavioral sciences, design and several other fields of study. HCI focuses on the challenges in making computers and computations useful, usable, and universally accessible to people. A basic goal of HCI is to improve the interactions between users and computers by making computers more usable and receptive to the user's needs. HCI is a multi-disciplinary field.
- 3. Cont… Human User Single or a group of users Important: designers of the system should understand who is going to use the system. Computer Any interactive technology that a user might use to accomplish a task. Interaction Any communication between the user and the computer. Occurs at the user interface (Hardware & software) E.g. characters or objects displayed by software on a personal computer's monitor E.g. input received from users via hardware peripherals such as keyboards and mice Important: interaction design should aim at supporting user tasks.
- 4. Some Aspects of HCI HCI is concerned with all those aspects that relate to the interaction between users and computers: 1. Methodologies and processes for designing interfaces (i.e., given a task and a class of users, design the best possible interface within given constraints, optimizing for a desired property such as learning ability or efficiency of use) 2. Methods for implementing interfaces (e.g. software toolkits and libraries; efficient algorithms) 3. Techniques for evaluating and comparing interfaces 4. Developing new interfaces and interaction techniques 5. Developing descriptive and predictive models and theories of interaction
- 5. Aims of HCI HCI aims at producing systems that are: 1. Useful or functional the system should accomplish what it is intended for or what is required. 2. Usable the system must allow users to accomplish tasks easily and naturally. the system must support user’s tasks 3. Used The system must make people want to use it. It should be attractive, engaging, fun etc. 4. safe The system should not put the health of users at risk.
- 6. Goals of HCI The goals of HCI can be explained as follows: 1. Usability: a key concept in HCI is concerned with making systems easy to learn and easy to use. the system should be easy to remember how to use. The system should be effective(useful, helpful) The system should be efficient (good at accomplishing user task) The system should be enjoyable If the system forces the user to adopt unacceptable mode of work then it is not usable.
- 7. Factors that affect Usability Input format- the format of input should not be difficult. Feedback- the system should give feedback or result of the action. Visibility- the mapping between control and effect. A control should give proper effect immediately. Affordance- the operations and manipulations of the control (command) Perceived affordance: describes what can be done to a control just by looking at it. Users should be able to figure out what can be done to the control just by looking at it. User-centred designs aim at putting the system in line with the user needs and understand user needs. Tools and techniques are required in order to develop systems that are usable.
- 8. Cont… 2. Proper functionality: the program works as it is expected to, e.g. a word processor is for typing documents into not playing games on (the things it can do). 3. Consistency: a control works the same way every time it is encountered, it's function does not change inside the program. For example, a user always clicks a button, they do not click it sometimes and type text into at other times. 4. Standardization: seeks consistency across programs so that, for example, a user could learn one word processor and then be able to use any word processor available to them, i.e. learn Microsoft Word and then be able use LibreOffice with a minimum of effort. 5. Reliability: the program works without a flaw, it does not lock up or crash.
- 9. Cont… 6. Security and Data Integrity: the program protects the users' data from unwanted tampering and alteration. Hackers and viruses are two of the most common threats to security and data integrity however flaws in the programs code (bugs) can also alter and/or destroy users' data without warning. 7. Integration: seeks to use multiple programs in conjunction with one another. e.g. Microsoft Office. In Office, you can type a document in Word and then insert a spreadsheet into the document or insert the document into a Power Point presentation. This is integration. 8. Portability: Portability refers to the ability to use one program on multiple operating systems without recompiling it for every system, i.e. be able to install and use Microsoft Office off the same CD on Macintosh, Linux, and Windows 8 machines.
- 10. Cont… Availability: Availability is the principle that if users cannot find or access a program they will not use it but if it is readily available, especially if it is more available than its competition, a user is more likely to use the program.
- 11. Fields Contributing to HCI HCI incorporates a range of skills from different disciplines. Computer science provides the technology needed for building systems. Psychology and cognitive science provides knowledge of the user’s perceptual, cognitive and problem solving skills. Social psychology provides knowledge of how society affect the use of the system. Also how society will be affected by the system. Helps to understand the wider context of the interaction.
- 12. Cont… Graphics design To produce an effective interface presentation Ergonomics For understanding the user’s physical capabilities to use the system. Business To be able to market the technology Artificial Intelligence Technical writing To produce the manuals Note: all this is too much for one person. That is why people tend to specialise in one field.
- 13. Components of HCI 1.The human 2. Computer 3.Interaction NYIRENDA M.13
- 14. The Human Human aspects for designers Designers must understand the capabilities and limitations of the user. Designers must understand the requirements of the user since computers are designed to assist the users. Cognitive psychology Is concerned with: 1. Perceptual system how humans perceive the world around them. Also known as Human Perception. Designers should be concerned with how the user will acquire information. 2. Information storage and processing how humans store and process information and solve problems. 3. How humans physically manipulate objects(Motor system)
- 15. The human perceptual system The user, one whom computers are designed to assist. Information i/o … A person’s interaction with the outside world is through info being received & sent (input & output) visual, auditory, haptic/touch, movement In an interaction with a computer, user receives info that is output by the computer, and responds by providing input to the computer. The user’s output becomes computer’s input and vice versa. Input in human occurs mainly through the senses and output through the motor control of the effectors. Major senses Sight Hearing Touch Taste Smell
- 16. Cont… Information stored in memory sensory, short-term, long-term Information processed and applied reasoning, problem solving, skill, error Emotion influences human capabilities Each person is different
- 17. Vision Is the primary source of info for average person Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus
- 18. Cont… On 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 hand the interpretive capabilities of visual processing allow images to be constructed from incomplete info Both of the above stages influence what can and what cannot be perceived visually by a human being, which in turn directly affects the way that we design computer systems.
- 19. The Eye - physical reception mechanism for receiving light and transforming it into electrical energy light reflects from objects images are focused upside-down on retina retina contains rods for low light vision and cones for colour vision ganglion cells (brain!) detect pattern and movement NOTE: Students to study the eye as a physical receptor.
- 20. Interpreting the signal Size and depth Reflected light from the object forms an upside down image on the retina visual angle indicates how much of view object occupies (relates to size and distance from eye) The visual angle is affected by both the size of the object and its distance from the eye. If two objects of the same size are placed at different distances from the eye, the furthest one will have the smaller visual angle. Visual angle is measured in degrees or minutes arc where: 1 degree is equivalent to 60 minutes of arc. 1 minute of arc is equivalent to 60 seconds of arc. if visual angle of an object is too small we will not be able to perceive it at all.
- 21. Cont… Visual acuity is the ability of a person to perceive fine detail(limited) Assuming that we can perceive the object, does its visual angle affect our perception of its size? Given that the visual angle of an object is reduced as it gets further away, we might expect that would expect that we would perceive the object as smaller. Perception of size relies on other factors than the visual angle (The law of size constancy). These factors are: depth and familiarity familiar objects perceived as constant size (in spite of changes in visual angle when far away) If we expect an object to be of a certain size then we can judge its distance accordingly. The size and height of the object in our field of view provides a cue to its distance.
- 22. Visual angle and perception of objects Objects of the same size at different distances have different visual angles. Visual angle
- 23. Interpreting the signal (cont) Brightness is the subjective reaction to levels of light affected by luminance of object Luminance the amount of light emitted by an object Luminance of an object is dependent on the amount of light falling on the object’s surface and its reflective properties. Brightness can be described in terms of luminance that gives a just noticeable difference in brightness Visual system compensates for changes in brightness. In dim light 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 luminance as does flicker The eye will perceive a light switched on and off rapidly as constantly on.
- 24. Interpreting the signal (cont) Contrast Related to luminance Is the difference in luminance between the object and its background.
- 25. Interpreting the signal (cont) Perceiving Colour made up of hue, intensity and saturation Hue – determined by spectral wavelength of light Blues have shorter wavelength, greens medium and reds long Intensity – is the brightness of the colour(amount of light emitted from the colour) Saturation – the amount of whiteness in the colour cones sensitive to colour wavelengths blue acuity is lowest 8% males and 1% females colour blind Colour vision is best at the fovea and waste at the periphery where rods predominate.
- 26. Limitations of visual interfaces The image is not completely visible but the eye concentrates in making a complete image The visual system compensates for: movement of the image on the retina which occurs as we move around and as the object we see moves. changes in luminance. The ability to interpret and exploit our expectations can be used to resolve ambiguities Optical illusions sometimes occur due to over compensation Images are interpreted according to what you expect Leads to creation of wrong interpretations from what is seen. (Ponzo Illusion)
- 27. Optical Illusions the Ponzo illusion the Muller Lyer illusion These illusions demonstrate that our perception of size is not completely reliable. Similarly colour and brightness are perceived as constant in spite of changes in luminance.
- 28. Reading Several stages: visual pattern of the word is perceived decoded using internal representation of language interpreted using knowledge of syntax, semantics, pragmatics Reading involves saccades (jerky movements) and fixations Perception occurs during fixations 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 Word shape is important to recognition 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(how easy it is to read a particular text)
- 29. Reading- cont… Reading from a computer screen is slower than from a book. This is due to the following: longer line length, fewer words to a page Orientation the familiarity of the medium of the page Negative contrast improves reading from computer screen i.e. Dark characters on a light screen provides higher luminance and, therefore, increased acuity, than a positive contrast. This will in turn increase legibility.
- 30. Hearing Provides information about environment: distances, directions, objects etc. 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. Physical apparatus (Ear): outer ear – has two parts: 1. the pinna - attached to the sides of the head 2. the auditory canal – along which sound waves are passed to the middle ear. –protects middle ear and amplifies sound middle ear – transmits sound waves as vibrations to inner ear inner ear – chemical transmitters are released and cause impulses in auditory nerve
- 31. Hearing- Cont… Sound sound is changes or vibrations in air pressure. Characteristics of sound: pitch – sound frequency - A low frequency produces a low pitch, a high frequency, a high pitch. loudness – amplitude of the sound timbre – type or quality of the sound - sounds may have the same pitch and loudness but be made by different instruments and so vary in timbre
- 32. Hearing- cont… Humans can hear frequencies from 20Hz to 15kHz But less accurate at distinguishing high frequencies than low. Auditory system filters sounds allows us to ignore background noise and concentrate on important information. can attend to sounds over background noise. E.g. the cocktail party phenomenon. - where we can pick out our name spoken across a crowded noisy room. sound can convey a remarkable amount of information. It is rarely used to its potential in interface design confined to warning sounds and notifications in interactive systems. exception is multimedia, which may include music, voice commentary and sound effects. sound could be used more extensively in interface design, to convey information about the system state
- 33. Non-speech sound Uses of non-speech sounds include the following: Attention – to attract the user’s attention to a critical situation or to the end of a process, for example. Status information – continuous background sounds can be used to convey status information. For example, monitoring the progress of a process (without the need for visual attention). Confirmation – a sound associated with an action to confirm that the action has been carried out. For example, associating a sound with deleting a file. Navigation – using changing sound to indicate where the user is in a system. For example, what about sound to support navigation in hypertext?
- 34. Touch Provides important feedback about environment. Can tell us when we touch something hot or cold & warn us May be key sense for someone who is visually impaired. Important in computer systems Feeling buttons depress is an important part of the task of pressing the button. Stimulus received via receptors in the skin: thermoreceptors – heat and cold nociceptors – pain mechanoreceptors – pressure Rapidly adapting- respond to immediate pressure. The stop if continuous pressure is applied Slowly adapting- respond to continuous applied pressure. Some areas more sensitive than others e.g. fingers.
- 35. Touch cont… Kinethesis - awareness of body position and limbs Due to receptors in the joints. Affects both comfort and performance. Types of Kinethesis Rapidly adapting – respond when a limb is moved in a particular direction. Slowly adapting – respond to both movement and static position. Position receptors – respond only when a limb is in static position.
- 36. Movement Time taken to respond to stimulus: reaction time + movement time Movement time dependent on age, fitness etc. Reaction time - dependent on stimulus type: visual ~ 200ms auditory ~ 150 ms pain ~ 700ms Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator.
- 37. Movement (cont) Fitts' Law describes the time taken to hit a screen target: Mt = a + b log2(D/S + 1) where: a and b are empirically determined constants Mt is movement time D is Distance S is Size of target ⇒targets as large as possible distances as small as possible
- 38. Human Memory Its job is to store and retrieve information Keeps factual knowledge, procedures undertaken and actions This allows humans to be able to repeat things or actions in future, To use language To use new information received via the senses Gives people the sense of identity by preserving information from our past experiences.
- 39. Types of Human Memory There are three types of memory function: Sensory memories Short-term memory or working memory Long-term memory Selection of stimuli governed by level of arousal. Attention Rehearsal
- 40. Sensory memory Act as buffers for stimuli received through senses Eyes: iconic memory- respond to visual stimuli Ears: echoic memory- respond to aural stimuli Skin: haptic memory- respond to tactile stimuli Information on these memories is continuously overwritten by new information coming in on these channels.
- 41. Short-term memory (STM) Used as a Scratch-pad for temporary recall of information. Advantage rapid access ~ 70ms Disadvantages rapid decay ~ 200ms limited capacity - 7± 2 chunks
- 42. Measuring memory Two methods for measuring memory capacity: The first involves determining the length of a sequence which can be remembered in order The second allows items to be freely recalled in any order 212348278493202 0121 414 2626 Difficult to remember the sequence of chunks below HEC ATR ANU PTH ETR EET Move last character to the first position becomes “the cat ran up the tree”
- 43. Long-term memory (LTM) Repository for all our knowledge slow access ~ 1/10 second slow decay, if any huge or unlimited capacity Two types episodic – serial memory of events semantic – structured memory of facts,concepts, skills semantic LTM derived from episodic LTM
- 44. Long-term memory (cont.) Semantic memory structure provides access to information represents relationships between bits of information supports inference Model: semantic network inheritance – child nodes inherit properties of parent nodes relationships between bits of information explicit supports inference through inheritance
- 45. LTM - semantic network
- 46. Models of LTM - Frames Information organized in data structures Slots in structure instantiated with values for instance of data Type–subtype relationships DOG Fixed legs: 4 Default diet: carniverous sound: bark Variable size: colour COLLIE Fixed breed of: DOG type: sheepdog Default size: 65 cm Variable colour
- 47. Models of LTM - Scripts Model of stereotypical information required to interpret situation Script has elements that can be instantiated with values for context Script for a visit to the vet Entry conditions: dog ill vet open owner has money Result: dog better owner poorer vet richer Props: examination table medicine instruments Roles: vet examines diagnoses treats owner brings dog in pays takes dog out Scenes: arriving at reception waiting in room examination paying Tracks: dog needs medicine dog needs operation
- 48. Models of LTM - Production rules Representation of procedural knowledge. Condition/action rules if condition is matched then use rule to determine action. IF dog is wagging tail THEN pat dog IF dog is growling THEN run away
- 49. LTM - Storage of information rehearsal information moves from STM to LTM total time hypothesis amount retained proportional to rehearsal time distribution of practice effect optimized by spreading learning over time structure, meaning and familiarity information easier to remember
- 50. LTM - Forgetting decay information is lost gradually but very slowly interference new information replaces old: retroactive interference old may interfere with new: proactive inhibition so may not forget at all memory is selective … … affected by emotion – can subconsciously `choose' to forget
- 51. LTM - retrieval recall information reproduced from memory can be assisted by cues, e.g. categories, imagery recognition information gives knowledge that it has been seen before less complex than recall - information is cue