HUMAN

1. HUMAN

2. Roadmap • Information I/O channels • Responding to stimulus • Human memory • Thinking • Errors and mental models • Emotion vs. human capabilities • Users’ individual differences • Psychology and the design of interactive systems

3. The Human • User – Information Processing System • Information • Comes in (Input) • Is stored (Memory) • Is processed (Processing) • Is passed out (Output)

4. Information I/O Channels • Information Input / Output: • Human being’s interaction dependent on information being received and given: input and output. • Interaction with computer • User receives information that is output by the computer • Responds by providing input to the computer • i.e. user’s output (user gives) becomes computer’s input and the user’s input (user receives) becomes the computer’s output.

5. Human I/O Channels • Input : Senses Involved • Visual sense/vision (sight) • Auditory sense/hearing (sound) • Sense of touch (hap tic) • Sense of smell • Sense of taste • Vision, hearing and touch are currently the ones being significantly used in HCI. • Output: Motor control of effectors • Effectors are body parts that can respond to stimulation e.g. fingers, eyes, head, foot, vocal system, etc

6. Example • Computer with keyboard and mouse • Application: GUI, Menus & Icons • Information Received • Sight • Ears • Touch • Information Sent • Hands: Keyboard, mouse

7. Vision Vision is primary source of information for humans • Visual Perception --Two stages • Physical reception of Stimulus • Processing and Interpretation of Stimulus

8. Eye and Interfaces • Interpretation and/or Perception of size and depth, brightness and color, each of which is crucial to the design of effective visual interfaces

9. Eye

10. 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 Photoreceptors: • Rods: Highly sensitive to light for low light vision • Cones: For colour vision • Ganglion cells detect • Pattern • movement

11. Interpreting the Signal • Size and depth • Visual Angle indicates how much of view object occupies • relates to size and distance from eye • Visual Acuityis ability to perceive detail • 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

12. Interpreting the Signal (cont) • Brightness • Subjective reaction to levels of light • Affected by luminance of object • Visual acuity increases with luminance as does flicker • Colour • Made up of hue, intensity, saturation • Cones sensitive to colour wavelengths • Red, Green, Blue • 8% males and 1% females colour blind

13. Interpreting the Signal - Colour • Hue • Hue is what most people think of when we say color • Hue is the name of a distinct color of the spectrum, It is the particular wavelength frequency • Saturation • Saturation is the purity of a colour • Value (Intensity, Brightness, Lightness) • Refers to the intensity of light present. When light is at its fullest intensity, colors will become bright • Unlike saturation, there isn't necessarily less of the color – it is just not as intense

14. 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

15. Interpreting the Signal • Ambiguity B or 13 ??? • Context is used to resolve ambiguity • Interpret & exploit the expectation

16. Optical Illusions The Muller Lyer illusion The Ponzo illusion The Proof Reading Illusion

17. 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

18. Hearing • Sound • Pitch – sound frequency • Loudness – amplitude • Timbre – type or quality

19. 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.

20. 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 • Question: Ecommerce (CDs & Books vs. Clothes)

21. Movement • Fitt’s Law: • Describes the time taken to hit a screen target Movement Time = a + b log2(D/S + 1) • where: • a and b are empirically determined constants • D is Distance from target centre • S is Size of target • Important: D & S are calculated along the axis of motion

22. Movement • Fitt’s Law Movement Time = a + b log2(D/S + 1) Index of Difficulty => Targets as large as possible=> Distances as small as possible

23. Movement • Pie-chart shaped menus • All options are equidistant (As opposed to lists) • Increased used of screen estate

24. Responding to Stimulus • Time taken to respond to stimulus = Reaction time + Movement time • Movement time: dependent on age, fitness, etc. • Reaction time: dependent on stimulus type e.g. • visual ~ 200ms • auditory ~ 150 ms • pain ~ 700ms • Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator.

25. HUMAN MEMORY There are three types of memory function: 1. Sensory memory 2. Short-term memory or working memory 3. Long-term memory • Selection of stimuli is governed by Level of Interest.

26. Human Memory

27. Sensory memory • Buffers for stimuli received through senses • Iconic memory: visual stimuli • Echoic memory: aural stimuli • Haptic memory: tactile stimuli • Continuously overwritten • Transmitted from Sensory Memory to Working Memory

28. Examples • During firework displays, moving sparklers leave a persistent image • Concentration of mind on one out of a number of competing stimuli or thoughts • As in cocktail party • Have you ever had someone ask you a question when you are reading? • You ask them to repeat the question, only to realize that you know what was asked after all.

29. Short Term Memory (STM) • Temporary recall of information • Reading a sentence, Performing an arithmetic operation etc. • Rapid access: order of 70ms • Rapid decay: order of 200ms • Limited capacity: 7± 2 chunks Chunking Information can increase short term memory Pattern Abstraction

30. Short-term memory (STM) • Examples • 212348278493202 • 44 113 245 8920 (chunks with pattern, easier to remember) • HEC ATR ANU PTH ETR EET (chunks without pattern, not easy to remember)

31. Long-term memory (LTM) • Repository for all our knowledge • Slow access ~ 1/10 second • Slow decay, if any • Huge or unlimited capacity

32. Long Term Memory How to ….. Facts Events and Experiences

33. Long Term Memory 1.Episodic memory: • It represents our memory of events and experiences in a serial form. • It is from this memory that we can reconstruct the actual events that took place at a given point in our lives. 2. Semantic memory: • It is a structured record of facts, concepts, skills that we have acquired. • It is structured in some way to allow access to information, representation of relationships between pieces of information, and inference.

34. Long-term Memory (cont.) • Memory models used to explain how we represent and store knowledge 1. Semantic networks 2. Frames 3. Scripts 4. Production system

35. 1. Semantic Networks • Represent the associations and relationships between items in memory.

36. 2. Frames • Extend semantic nets to include structured, hierarchical information. • They represent knowledge items in a way which makes explicit the relative importance of each piece of information. • 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

37. 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 3. Scripts • Attempt to model the representation of stereotypical knowledge about situations. • Model of stereotypical information required to interpret situation. • Script has elements that can be instantiated with values for context.

38. 4. Production System • 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

39. Long Term Memory -- Processes • Storage • Forgetting • Retrieval

40. LTM - Storage of information 1. Rehearsal • Information moves from STM to LTM • Total Time hypothesis • Amount of information retained is proportional to rehearsal (or learning) time • Distribution of practice effect • Optimized by spreading learning over time 2. Structure, Meaning and Familiarity • If information is Structured, Meaningful or Familiar, it becomes easier to remember Past, Faith, Idea, Cold, Value, Courtesy, Logic, Quiet, Ambitious Boat, Tree, Cat, Child, Gun, Plate, Home, Table, Computer, Spoon

41. LTM - Forgetting 1. Decay • Information is lost gradually but very slowly 2. Interference • New information replaces old: Retroactive interference • e.g. if you change telephone numbers, learning your new number makes it more difficult to remember your old number. • However sometimes the old may interfere with new: proactive inhibition • e.g. when you find yourself driving to your old house rather than your new one. 3. Emotion • We tend to remember highly emotive events rather than mundane ones. Do we ever actually forget anything or does it just become increasingly difficult to access certain items from memory? (debatable)

42. LTM - Retrieval • Recall • Information reproduced from memory can be assisted by cues, e.g. Categories, imagery • Act of reproducing a specific incident, fact or other item (from LTM) • Recalling where you were last weekend, fill-in-the-blank on exams • Recognition • Information gives knowledge that it has been seen before • Less complex than recall • People are more likely to recognize a suspect in a police line-up than to provide an accurate description from recall memory • It is easier to answer multiple-choice questions than essay questions because the correct answer may be recognized

43. THINKING • Reasoning • Deduction • Induction • Abduction • Problem solving

44. Reasoning Use the knowledge we have to draw conclusion or infer something new about the domain of interest • Deductive Reasoning • Inductive Reasoning • Abductive Reasoning

45. Reasoning by Deduction • 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

46. Reasoning by Deduction (cont.) • When truth and logical validity clash … e.g. Some people are babies Some babies cry Inference - Some people cry • In this context, why do we infer incorrectly? We bring our world knowledge into the reasoning process i.e. we assume all babies are people [even when we are not explicitly told so].

47. Reasoning by Induction • 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.

48. 7E 4 K Reasoning by Induction Wason's cards Which cards would you need to pick up to test the truth of the statement ‘If a card has a vowel on one side it has an even number on the other’? A common response to this is to check the E and the 4. Wrong! This uses only positive evidence. In fact, to test the truth of the statement we need to check negative evidence: if we can find a card which has an odd number on one side and a vowel on the other we have disproved the statement. We must therefore check E and 7. (It does not matter what is on the other side of the other cards: the statement does not say thatall even numbers have vowels, just that all vowels have even numbers.) If a card has a vowel on one side it has an even number on the other

49. Reasoning by Abduction • Reasoning from Event to Cause • e.g. Sam drives fast when angry. • If I see Sam driving fast, assume angry. • Unreliable: • Can lead to false explanations

50. Problem Solving • Reasoning: Inferring new information from what is known • Problem Solving: Finding solution to unfamiliar task using knowledge • Several Theories: • Gestalt theory • Problem space theory • Analogy • Mapping: Using knowledge of similar problems/domains • Skill acquisition • Driver, Player, Surgeon