HCI Lecture 1
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This document provides an overview of human psychology and cognition, including: - The human senses of vision, hearing, touch, and movement and how we process sensory information. - Memory systems including sensory memory, short-term memory, and long-term memory. - Thinking processes such as reasoning, problem solving, and decision making. - How emotion influences human capabilities and performance. - Individual differences in human abilities and how they may impact design. - Implications for designing interactive systems based on principles of human psychology.
HCI Lecture 1
- 2. the human • Information i/o … – visual, auditory, haptic, movement • 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
- 3. Vision Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus
- 4. 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
- 5. Interpreting the signal • Size and depth – visual angle indicates how much of view object occupies (relates to size and distance from eye) – visual acuity is ability to perceive detail (limited) – familiar objects perceived as constant size (in spite of changes in visual angle when far away) – cues like overlapping help perception of size and depth
- 6. Interpreting the signal (cont) • Brightness – subjective reaction to levels of light – affected by luminance of object – measured by just noticeable difference – visual acuity increases with luminance as does flicker • Colour – made up of hue, intensity, saturation – cones sensitive to colour wavelengths – blue acuity is lowest – 8% males and 1% females colour blind
- 7. Interpreting the signal (cont) • The visual system compensates for: – movement – changes in luminance. • Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation
- 8. Optical Illusions the Ponzo illusion the Muller Lyer illusion
- 9. Reading • Several stages: – visual pattern perceived – decoded using internal representation of language – interpreted using knowledge of syntax, semantics, pragmatics • Reading involves saccades and fixations • Perception occurs during fixations • Word shape is important to recognition • Negative contrast improves reading from computer screen
- 10. Hearing • Provides information about environment: distances, directions, objects etc. • 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 • Sound – pitch – sound frequency – loudness – amplitude – timbre – type or quality
- 11. Hearing (cont) • 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.
- 12. Touch • Provides important feedback about environment. • May be key sense for someone who is visually impaired. • 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. • Kinethesis - awareness of body position – affects comfort and performance.
- 13. 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.
- 14. 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
- 15. 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.
- 16. sensory memory • Buffers for stimuli received through senses – iconic memory: visual stimuli – echoic memory: aural stimuli – haptic memory: tactile stimuli • Examples – “sparkler” trail – stereo sound • Continuously overwritten
- 17. Short-term memory (STM) • Scratch-pad for temporary recall – rapid access ~ 70ms – rapid decay ~ 200ms – limited capacity - 7± 2 chunks
- 18. Examples 212348278493202 0121 414 2626 HEC ATR ANU PTH ETR EET
- 19. 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
- 20. 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
- 21. LTM - semantic network
- 22. 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
- 23. 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
- 24. 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
- 25. 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
- 26. 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
- 27. 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
- 29. 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
- 30. 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
- 31. 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.
- 32. 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
- 33. 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
- 34. 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
- 35. 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
- 36. 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
- 37. 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
- 38. 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
- 39. 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)
- 40. 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
- 41. 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?
- 42. 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)