Human Computer Interaction Unit 1 Chapter 1 Presentation.ppt
- 1. Unit 1
- 2. Introduction • Human–computer interaction (HCI), alternatively man–machine interaction (MMI) or computer–human interaction (CHI) is the study of interaction between people (users) and computers. • HCI is undoubtedly a multi-disciplinary subject • HCI involves the design, implementation and evaluation of interactive systems
- 3. Introduction • 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. • 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
- 4. WHY HUMAN–COMPUTER INTERACTION? • this word processor no longer has a delete option in its menu • Errors such as these, resulting from poor design choices, happen every day. Perhaps they are not catastrophic: • when computers are marketed as ‘user friendly’ and ‘easy to use’, simple mistakes like this can still occur? • 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.
- 6. • Involve the users Where possible, the eventual users should be involved in the design process. • They have vital knowledge 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 • Automatic syringe: setting the dose to 1372 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
- 7. • 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. • A long term goal of HCI is – to design systems that minimize the barrier between the human's cognitive model of what they want – to accomplish and the computer's understanding of the user's task
- 8. Introduction • we introduce the fundamental components of an interactive system: the human user, the computer system itself and the nature of the interactive process • 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. • Chapter 2 - 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 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
- 9. the human • Information is received and responses given via a number of input and output channels – visual, auditory, haptic, movement • Information is stored in memory – sensory, short-term, long-term • Information is processed and applied – reasoning, problem solving, skill, error • Emotion influences human capabilities
- 10. Vision • It is the primary source of information for the average person • Two stages in vision – physical reception of stimulus from the outside world – processing and interpretation of stimulus • eye as a physical receptor
- 11. 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 detect pattern and movement
- 12. The human eye
- 13. • 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 contains two types of photoreceptor: – rods and cones • Rods are highly sensitive to light. they are unable to resolve fine detail • There are approximately 120 million rods per eye which are mainly situated towards the edges of the retina • Cones are the second type of receptor in the eye. They are less sensitive to 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
- 14. • 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 • 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 detection of pattern; – Y-cells which are more widely distributed in the retina and are responsible for the early detection of movement.
- 15. Interpreting the signal • Size and depth – The size of that image is specified as a visual angle – visual angle indicates how much of view object occupies (relates to size and distance from eye) – if two objects are at the same distance, the larger one will have the larger visual angle. – if two objects of the same size are placed at different distances from the eye, the furthest one will have the smaller visual angle • 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
- 16. • 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
- 17. • Visual acuity is the ability of a person to perceive fine detail • number of measurements have been established to test visual acuity, most of which are included in standard eye tests • 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
- 18. Interpreting the signal (cont) • A second aspect of visual perception is the perception of brightness. • Brightness – subjective reaction to levels of light – affected by luminance of 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
- 19. • Colour – made up of hue, intensity, saturation – Hue is determined by the spectral wavelength of the light. Blues have short wavelengths, greens medium and reds long – Intensity is the brightness of the color – saturation is the amount of whiteness in the color – The eye perceives color because the cones are sensitive to light of different wavelengths. – There are three different types of cone, each sensitive to a different color (blue, green and red).
- 20. limitations of visual processing • Visual processing involves the transformation and interpretation of a complete image, from the light that is thrown onto the retina. • 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 • The visual system compensates for: – movement – changes in luminance. • Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation allows our expectations to clearly disambiguate the interpretation of the object, as either a B or a 13.
- 21. Optical Illusions the Muller Lyer illusion 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. expectations compensating an image is the proofreading illusion 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.
- 22. The Ponzo illusion – are these the same size? Here the top line appears longer, owing to the distance effect, although both lines are the same length. These illusions demonstrate that our perception of size is not completely reliable.
- 23. Reading • Several stages: – 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 language processing include syntactic and semantic analysis and operate on phrases or sentences. • 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 • 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 • there is evidence that reading from a computer screen is slower than from a book
- 24. Hearing • Provides information about environment: distances, directions, objects etc. • 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. – tell where the sounds are coming from – 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
- 25. human ear • 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. • outer ear – 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. – 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
- 26. • The middle ear is a small cavity – connected to the outer ear by the tympanic membrane, or ear drum, – connected 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. – unlike the air-filled outer and middle ears, the inner ear is filled with a denser cochlean liquid. – By transmitting sound waves via the ossicles the sound waves are concentrated and amplified. • Physical apparatus: – outer ear – protects inner 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
- 27. Processing sound • sound is changes or vibrations in air pressure • Pitch is the frequency of the sound. • A low frequency produces a low pitch, a high frequency, a high pitch. • Loudness is proportional to the amplitude of the sound; the frequency remains constant. • Timbre relates to the type of the sound • sounds may have the same pitch and loudness but be made by different instruments and so vary in timbre. • The human ear can hear frequencies from about 20 Hz to 15 kHz • the ear can differentiate quite subtle sound changes and can recognize familiar sounds without concentrating attention on the sound source. • It is rarely used to its potential in interface design, usually being confined to warning sounds and notifications
- 28. Suggest ideas for an interface which uses the properties of sound effectively • Speech sounds can obviously be used to convey information. – This is useful not only for the visually impaired but also for any application where the user’s attention has to be divided • Attention – to attract the user’s attention to a critical situation or to the end of a process – Status information – continuous background sounds can be used to convey status information. • monitoring the progress of a process – Confirmation – a sound associated with an action to confirm that the action has been carried out. • associating a sound with deleting a file. – Navigation – using changing sound to indicate where the user is in a system. • what about sound to support navigation in hypertext?
- 29. Touch • touch or haptic perception. • Provides important feedback about environment. – It tells us when we touch something hot or cold, and can therefore act as a warning • May be key sense for someone who is visually impaired. • The skin contains three types of sensory receptor • Stimulus received via receptors in the skin: – thermoreceptors – heat and cold – nociceptors – pain – mechanoreceptors – pressure (some instant, some continuous) • Some areas more sensitive than others e.g. fingers.
- 30. • There are two kinds of mechanoreceptor, which respond to different types of pressure. • Rapidly adapting mechanoreceptors respond to immediate pressure as the skin is indented. – These receptors also react more quickly with increased pressure. – However, they stop responding if continuous pressure is applied. • Slowly adapting mechanoreceptors respond to continuously applied pressure • the whole of the body contains such receptors • some areas have greater sensitivity or acuity than others. • It is possible to measure the acuity of different areas of the body using the two-point threshold test
- 31. two-point threshold test • Take two pencils, held so their tips are about 12 mm apart. • Touch the points to your thumb and see if you can feel two points. • If you cannot, move the points a little further apart. • When you can feel two points, measure the distance between them. • The greater the distance, the lower the sensitivity
- 32. • haptic perception is kinesthesis • kinesthesia, is the perception of body movements. It involves being able to detect changes in body position and movements without relying on information from the five senses – awareness of the position of the body and limbs – This is due to receptors in the joints. – Again there are three types • rapidly adapting, which respond when a limb is moved in a particular direction • slowly adapting, which respond to both movement and static position; • positional receptors, which only respond when a limb is in a static position. • perception affects both comfort and performance. • For example, for a touch typist, awareness of the relative positions of the fingers and feedback from the keyboard are very important.
- 33. • E-commerce has become very successful in some areas of sales, such as travel services, books and CDs, and food. However, in some retail areas, such as clothes shopping, e-commerce has been less successful. Why? • With clothes, the experience of shopping is far more important • We need to be able to handle the goods, feel the texture of the material, check the weight to test quality. • demonstration environment called TouchCity allows people to walk around a virtual shopping mall, pick up products and feel their texture and weight. • haptic experience requires expensive hardware not yet available to the average e-shopper
- 34. Movement • A simple action such as hitting a button in response to a question involves a number of processing stages. The stimulus (of the question) is received through the sensory receptors and transmitted to the brain. The question is processed and a valid response generated. The brain then tells the appropriate muscles to respond. Each of these stages takes time, which can be roughly divided into reaction time and movement time. • Time taken to respond to stimulus: reaction time + movement time • Speed and accuracy of movement are important considerations in the design of interactive systems • Movement time dependent on age, fitness etc • Reaction time varies according to the sensory channel through which the stimulus is received – visual ~ 200ms – auditory ~ 150 ms – pain ~ 700ms • second measure of motor skill is accuracy. One question that we should ask is – whether speed of reaction results in reduced accuracy
- 35. 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 • The target may be a button, a menu item or an icon • The time taken to hit a target is a function of the size of the target and the distance that has to be moved. targets as large as possible distances as small as possible
- 36. 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.
- 37. • our memory contains our knowledge of actions or procedures. • It allows us to repeat actions, to use language, and to use new information received via our senses. • It also gives us our sense of identity, by preserving information from our past experiences • Memory is the second part of our model of the human as an information-processing system. • three types of memory or memory function: sensory buffers, short-term memory or working memory, and long-term memory
- 38. sensory memory • Buffers for stimuli received through senses • A sensory memory exists for each sensory channel: – iconic memory: visual stimuli – echoic memory: aural stimuli – haptic memory: tactile stimuli • These memories are constantly overwritten by new information coming in on these channels • Information is passed from sensory memory into short-term memory by attention, thereby filtering the stimuli to only those which are of interest at a given time • Attention is the concentration of the mind on one out of a number of competing stimuli or thoughts • Information received by sensory memories is quickly passed into a more permanent memory store, or overwritten and lost.
- 39. Short-term memory (STM) • Short-term memory or working memory acts as a ‘scratch-pad’ for temporary recall of information. • It is used to store information which is only required fleetingly • calculate the multiplication 35 * 6 in your head – To perform calculations such as this we need to store the intermediate stages for use later • Reading – In order to comprehend this sentence you need to hold in your mind the beginning of the sentence as you read the rest. • Short-term memory can be accessed rapidly, in the order of 70 ms. – decays rapidly • meaning that information can only be held there temporarily, in the order of 200 ms. • Short-term memory also has a limited capacity
- 40. • two basic 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.
- 41. Examples how many digits could you remember? 212348278493202 the average person can remember 7 + or - 2 digits Did you recall that more easily? Here the digits are grouped or chunked 0121 414 2626 chunking information can increase the short-term memory capacity HEC ATR ANU PTH ETR EET the cat ran up the tree moving the last character to the first position the sequence is easy to recall.
- 42. • recency effect – evidence shows that recall of the last words presented is better than recall of those in the middle – if the subject is asked to perform another task between presentation and recall (for example, counting backwards) the recency effect is eliminated. • The recall of the other words is unaffected. • that short-term memory recall is damaged by interference of other information
- 43. Long-term memory (LTM) • long-term memory is our main resource. • Here we store factual information, experiential knowledge, procedural rules of behavior • Repository for all our knowledge – slow access ~ 1/10 second – slow decay, if any – huge or unlimited capacity • It differs from short-term memory in a number of significant ways. – First, it has a huge, if not unlimited, capacity. – Secondly, it has a relatively slow access time of approximately a tenth of a second. – Thirdly, forgetting occurs more slowly in long-term memory
- 44. Long-term memory (cont.) • Long-term memory structure • two types of long-term memory – episodic memory and semantic memory • Episodic memory represents our memory of events and experiences in a serial form • Semantic memory structure – provides access to information – represents relationships between bits of information – supports inference • representation of knowledge – semantic network – Frames – script – Representation of procedural knowledge
- 45. LTM - semantic network
- 46. Models of LTM - Frames • A number of other memory structures have been proposed to explain how we represent and store different types of knowledge • Semantic networks represent the associations and relationships between single items in memory. • However, they do not allow us to model the representation of more complex objects or events – which are perhaps composed of a number of items or activities. • Structured representations such as frames and scripts organize information into data structures. • Slots in these structures allow attribute values to be added. 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 Scripts attempt to model the representation of stereotypical knowledge about situations John took his dog to the surgery. After seeing the vet, he left. 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. • A script comprises a number of elements, which, like slots, can be filled with appropriate information: • Entry conditions Conditions that must be satisfied for the script to be activated. • Result Conditions that will be true after the script is terminated. • Props Objects involved in the events described in the script. • Roles Actions performed by particular participants. • Scenes The sequences of events that occur. • Tracks A variation on the general pattern representing an alternative scenario.
- 49. Models of LTM - Production rules Representation of procedural knowledge. • Condition–action rules are stored in long-term memory. • Information coming into short-term memory can match a condition in one of these rules and result in the action being executed 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
- 50. LTM - Storage of information • There are three main activities related to long-term memory: – storage or remembering of information – forgetting – information retrieval • First, how does information get into long-term memory and how can we improve this process? • Information from short-term memory is stored in long-term memory by rehearsal. • The repeated exposure to a stimulus or the rehearsal of a piece of information transfers it into long-term memory
- 51. LTM - Forgetting • There are two main theories of forgetting: – decay and interference. decay – information is lost gradually but very slowly interference • If we acquire new information it causes the loss of old information. – This is termed retroactive interference. – you change telephone numbers, • Sometimes the old memory trace breaks through and interferes with new information. – This is called proactive inhibition. – find yourself driving to your old house rather than your new one
- 52. LTM - retrieval • two types of information retrieval, recall and recognition recall • In recall the information is reproduced from memory • recall can be assisted by the provision of retrieval cues, which enable the subject quickly to access the information in memory • For example, consider the following list of words: • child red plane dog friend blood cold tree big angry • Now make up a story that links the words using as vivid imagery as possible. Now try to recall as many of the words as you can recognition – information gives knowledge that it has been seen before – less complex than recall - information is cue
- 54. Deductive Reasoning • Deduction: – derive logically necessary conclusion from given premises. e.g. If it is Friday then she will go to work It is Friday Therefore she will go to work. • Logical conclusion not necessarily true: e.g. If it is raining then the ground is dry It is raining Therefore the ground is dry
- 55. Deduction (cont.) • When truth and logical validity clash … e.g. Some people are babies Some babies cry Inference - Some people cry Correct? • People bring world knowledge to bear
- 56. Inductive Reasoning • Induction: – generalize from cases seen to cases unseen e.g. all elephants we have seen have trunks therefore all elephants have trunks. • Unreliable: – can only prove false not true … but useful! • Humans not good at using negative evidence e.g. Wason's cards.
- 57. Wason's cards Is this true? How many cards do you need to turn over to find out? …. and which cards? If a card has a vowel on one side it has an even number on the other 7 E 4 K
- 58. Abductive reasoning • reasoning from event to cause e.g. Sam drives fast when drunk. If I see Sam driving fast, assume drunk. • Unreliable: – can lead to false explanations
- 59. Problem solving • Process of finding solution to unfamiliar task using knowledge. • Several theories. • Gestalt – problem solving both productive and reproductive – productive draws on insight and restructuring of problem – attractive but not enough evidence to explain `insight' etc. – move away from behaviourism and led towards information processing theories
- 60. Problem solving (cont.) Problem space theory – problem space comprises problem states – problem solving involves generating states using legal operators – heuristics may be employed to select operators e.g. means-ends analysis – operates within human information processing system e.g. STM limits etc. – largely applied to problem solving in well-defined areas e.g. puzzles rather than knowledge intensive areas
- 61. Problem solving (cont.) • Analogy – analogical mapping: • novel problems in new domain? • use knowledge of similar problem from similar domain – analogical mapping difficult if domains are semantically different • Skill acquisition – skilled activity characterized by chunking • lot of information is chunked to optimize STM – conceptual rather than superficial grouping of problems – information is structured more effectively
- 62. Errors and mental models Types of error • slips – right intention, but failed to do it right – causes: poor physical skill,inattention etc. – change to aspect of skilled behaviour can cause slip • mistakes – wrong intention – cause: incorrect understanding humans create mental models to explain behaviour. if wrong (different from actual system) errors can occur
- 63. Emotion • Various theories of how emotion works – James-Lange: emotion is our interpretation of a physiological response to a stimuli – Cannon: emotion is a psychological response to a stimuli – Schacter-Singer: emotion is the result of our evaluation of our physiological responses, in the light of the whole situation we are in • Emotion clearly involves both cognitive and physical responses to stimuli
- 64. Emotion (cont.) • The biological response to physical stimuli is called affect • Affect influences how we respond to situations – positive creative problem solving – negative narrow thinking “Negative affect can make it harder to do even easy tasks; positive affect can make it easier to do difficult tasks” (Donald Norman)
- 65. Emotion (cont.) • Implications for interface design – stress will increase the difficulty of problem solving – relaxed users will be more forgiving of shortcomings in design – aesthetically pleasing and rewarding interfaces will increase positive affect
- 66. Individual differences • long term – sex, physical and intellectual abilities • short term – effect of stress or fatigue • changing – age Ask yourself: will design decision exclude section of user population?
- 67. Psychology and the Design of Interactive System • Some direct applications – e.g. blue acuity is poor blue should not be used for important detail • However, correct application generally requires understanding of context in psychology, and an understanding of particular experimental conditions • A lot of knowledge has been distilled in – guidelines (chap 7) – cognitive models (chap 12) – experimental and analytic evaluation techniques (chap 9)