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CS422 - Human Computer Interaction

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  1. CS422 - Human Computer Interaction Instructor: Mehwish Aziz Spring: Fall 2010 Lecture 4-6


  3. Model Human Processor • Way back in 1983, Card, Moran and Newell gave a Model Human Processor - Simplified view of human processing involved on interaction with computer system. This view comprises of: • Perceptual System (Input-Output) – handling sensory stimulus from outside world • Motor system (Memory) – controlling actions • Cognitive system (Processing) – providing processing required for the two • Inspired from the above analogy, we consider today human user as information processing system • External factors like social and organizational environment • Moving ahead – let’s see what we will cover on ‘HUMAN’

  4. Outline • How Limited Capacity to process information is a major implication for design? • Limited Capacity as Human possess: • Limited numbers of receivable and reception channels • Limited Memory • Varying criteria to process and apply information • Emotions

  5. Outline • Limited numbers of receivable and reception channels • visual channel • auditory channel • movement • haptic channel • Limited Memory • sensory memory • short-term (working) memory • long-term memory

  6. Outline • Varying criteria to process and apply information: • reasoning • problem solving • skill acquisition • error • Emotion influences human capabilities • Users share common capabilities but are individuals with differences, which should not be ignored.

  7. Input-Output Channels • Input-Output Channels of Human: • Input Channels – Senses • Output Channels – Motor control of the effectors • Out of all senses – Vision, Hearing and Touch are major ones for HCI • Effectors – limbs, fingers, eyes, head and vocal system

  8. Input-Output Channels • Simplest Example – when you use PCs • Sight to view information • Touch to prompt input to PC through h/w interface • Hearing – when a system beeps on your mistake • Vocals – when giving a command through speech or say video presentation • Is computers Interaction today on a balance for both disabled and normal human?

  9. Human Vision • Vision has two stages • Physical reception of stimulus • Processing and interpretation of stimulus • Physical Reception of stimulus • Mechanisms 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 color vision • Ganglion cells (brain!) detect pattern and movement

  10. Processing and Interpretation of Stimulus • Identification of Size & Depth • Visual angle indicates how much of view object occupies (relates to size and distance from eye) • Visual Acuity is ability to perceive details (limited) • Familiar objectsperceived as constant size (in spite of changes in visual angle when far away) • Cues like overlapping help perception of size and depth

  11. Processing and Interpretation of Stimulus • Brightness • Subjective reactions to levels of light • Affected by luminance of objects • Measured by just noticeable differences • Visual Acuity increases with luminance as does flicker • Color • Composed of hew, intensity and saturation • Cones sensitive to color wavelengths • Blue Acuity is lowest • Color Blindness - 8% Males and 1% Females

  12. Processing and Interpretation of Stimulus • Visual Systems compensates for: • Movement • Changes in Luminance • Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation

  13. Optical Illusions the Muller Lyer illusion the Ponzo illusion

  14. Is this text Correct? the quick brown fox jumps over the the lazy dog

  15. Design Focus • Optical Illusion highlight the difference between way things are and way we perceive them • In interface design we need to be aware that we will not perceive things exactly as they are! • Optical Illusion also affects page symmetry • In graphic design there is a phenomena known as optical centersaying that • See the center of page a little above than actual center • Bottom page margins tend to be increased by 50% to compensate incase page is arranged by actual center

  16. Reading • Reading is performed with certain stages • Visual Patterns perceived • Decoded using internal representation of language • Interpretedusing knowledge of syntax, semantics, and pragmatics • Reading involves saccades and fixations • Perceptionsoccurs during fixations • Word shape is important to recognition • Negative contrast improves reading from computer screen • For negative contrasts - Lets review some web-pages

  17. The question persists and indeed grows whether the computer will make it easier or harder for human beings to know who they really are, to identify their real problems, to respond more fully to beauty, to place adequate value on life, and to make their world safer than it now is. Norman Cousins – The Poet and the Computer, 1966

  18. The question persists and indeed grows whether the computer will make it easier or harder for human beings to know who they really are, to identify their real problems, to respond more fully to beauty, to place adequate value on life, and to make their world safer than it now is. Norman Cousins – The Poet and the Computer, 1966

  19. Hearing • Provides information about environment • distances, directions, objects etc. • Physical apparatus: • outer ear – protects inner 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 • Sound • Pitch – sound frequency • loudness – amplitude • Timbre – type or quality

  20. Hearing • Humans can hear frequencies from 20Hz to 15kHz • less accurate distinguishing high frequencies than low • Auditory system filters sounds • can attend to sounds over background noise • for example, the cocktail party phenomenon • Different applications are using sound speech to • convey information or generate requests for user commands

  21. Hearing • Uses of non-speech sound include the following: • Attention – to attract user’s attention to an alarming state or end of the process • Status Information – continuous background sounds can be used to convey status information • especially where continuous visual attention is difficult • Confirmation – a sound with an action to confirm that the action has been carried out • Navigation – using changing sound to indicate where the user is in a system say • a sound to support navigation hypertext

  22. Touch • Provides important feedback about environment • Can be a key sense for one who is visually impaired • Stimulus received via the following receptors in the skin • Thermo-receptors – heat and cold • Nociceptors – pain • Mechanoreceptors – pressure (some instant or continuous) • Some areas are more sensitive than others e.g. fingers

  23. Touch • Kinaesthesia - awareness of body position • affects comfort and performance • E-Commerce seems to be very successful when it comes to shop for travel services, books and Computer accessories/ Softwares ….. • What about clothes shopping through e-commerce? Do you know about TouchCity?

  24. Movement • Time taken to respond to stimulus say hitting a button in response to a question • reaction time + movement time • Reaction time depends on information • Received by sensory receptors transmitted to brain • Brain’s processing to generate a response • Movement time is dependent on • age, fitness etc. • Reaction time - depends on stimulus type • Visual ~ 200ms • Auditory ~ 150 ms • Pain ~ 700ms

  25. Movement • Increasing reaction time decreases accuracy only in the unskilled operator • How pie chart-shaped menus are preferable to list since all options are equidistant? • Fitts' Law describes the time taken to hit a screen target • Mt = a + b log2(D/S + 1) Here; aand b are empirically determined constants • Mt -> movement time, D -> Distance , S -> Size of target => targets as large as possible distances as small as possible

  26. Touch + Movement • Haptics is the science of applying tactile sensation to human interaction with computers. • Haptic deviceis one that involves physical contact between the computer and the user • This enables human to feed information to computer & also receive information through felt sensation on some part of the body – Haptic Interface • Through an input/output device, such as a joystick or data gloves, that senses the body's movements • For example, in a virtual reality environment, a user can pick up a virtual tennis ball using a data glove

  27. Attention Rehearsal Memory • There are three types of memory function: Sensory memories (Iconic, Echoic, Haptic) Short-term memory or working memory Long-term memory

  28. Sensory Memory • Buffers for stimuli received through senses • iconic memory: visual stimuli • echoic memory: aural stimuli • haptic memory: tactile stimuli • Examples • “sparkler” trail / fireworks persistent image • stereo sound / ascertain the direction of sound origin • Continuously overwritten or lost

  29. Short Term Memory (STM) • Scratch-pad for temporary recall • rapid access ~ 70ms • rapid decay ~ 200ms • limited capacity - 7± 2 chunks • Examples • 212348278493202 • 0121 414 2626 • HEC ATR ANU PTH ETR EET (move last to one)

  30. 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 -> derived from episodic memory based experiences • semantic LTM derived from episodic LTM

  31. Long Term Memory (LTM) • Semantic memory structure • provides access to information • represents relationships between bits of information • supports inference (deductions) • Model: semantic network • inheritance – child nodes inherit properties of parent nodes • relationships between bits of information is explicit • supports inference through inheritance

  32. LTM – Semantic Network

  33. Models of LTM - Frames • Information organized in data structures using slots and frames • Slots in structure instantiated with values for instance of data • Frames slots may contain default, fixed or variable information • Type–subtype relationships COLLIE Fixed breed of: DOG type: sheepdog Default size: 65 cm Variable color DOG Fixed legs: 4 Default diet: carnivorous sound: bark Variable size: color:

  34. Script for a visit to the vet 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 Entry conditions: dog ill vet open owner has money Result: dog better owner poorer vet richer Props: examination table medicine instruments Models of LTM - Scripts • Model of stereotypical information required to interpret situation • Script has elements that can be instantiated with values for context • “John took his dog to the surgery. After seeing the web , he left.”

  35. 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

  36. 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

  37. 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

  38. 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

  39. Thinking - Reasoning • Reasoning deduction, induction, abduction • 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

  40. Thinking - Reasoning • Deduction: When truth and logical validity clash … e.g. Some people are babies Some babies cry • Inference - Some people cry • Correct? • 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.

  41. Thinking - Reasoning • 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

  42. Thinking – Problem Solving • Process of finding solution to unfamiliar task using knowledge. • Several theories exist. • Gestalt Theory: • 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

  43. Thinking – Problem Solving • 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

  44. Thinking – Problem Solving • 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

  45. Errors & Mental Models • 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

  46. 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

  47. Emotion • 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)

  48. Emotion + Individual Differences • Implications for interface design • Stress: increase difficulty of problem solving • Relaxed users: more forgiving of shortcomings in design • aesthetically pleasing and rewarding interfaces: increase positive affect • 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?

  49. Psychology & Designing Interactive Design • 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, • 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)