1. Human Abilities and Models Sensory and cognitive abilities and models, models of human performance

2. Outline Human capabilities and disabilities Senses Motor systems Memory Cognitive Processes Selective attention, learning, problem solving, language Contextual models

3. Typical Person Do we really have limited memory capacity?

4. Basic Human Capabilities Do not change very rapidly Not like Moore’s law! Have limits, which are important to understand Why do we care? Better design! Want to improve user performance Universal design – designing for all people, including those with disabilities

5. But… we’re all disabled sometimes Environment Fatigue Injury Aging Changing role of information technology

6. Usable Senses The 5 senses (sight, sound, touch, taste and smell) are used by us every day each is important on its own together, they provide a fuller interaction with the natural world Computers rarely offer such a rich interaction Can we use all the available senses? ideally, yes practically – no We can use sight sound touch (sometimes) We cannot (yet) use taste smell

7. Vision Fundamentals Retina has 6.5 M cones (color vision), mostly at fovea (1/3)˚ About 150,000 cones per square millimeter Fewer blue sensing cones than red and green at fovea 100 M rods (night vision), spread over retina, none at fovea Adaptation Switching between dark and light causes fatigue

8. Vision implications (more to come in visual design) Color Distinguishable hues optical illusions Acuity Determines smallest size we can see Less for blue and yellow than for red and green

9. Color/Intensity Discrimination The 9 hues most people can identify are: ColorWavelength Red629 Red-Orange596 Yellow-Orange582 Green-Yellow571 Yellow-Green538 Green510 Blue-Green491 Blue481 Violet-Blue460

10. Color Surround Effect Our perception of a color is affected by the surrounding color

11. Vision Difficulties Color blindness About 9 % of males are red-green colorblind! See http://colorlab.wickline.org/colorblind/colorlab/ Low-vision The vast majority of visually disabled people have some sight Blindness Rely on other senses to receive information Specialized hardware and software Screen readers Braille printers, etc.

12. Myopia and Hypermetropia Myopia Hypermetropia (short-sighted) (far-sighted)

13. Macular degeneration

14. Diabetic retinopathy

15. Cataracts

16. Tunnel vision

17. Accommodating Partial Sight Large monitor, high resolution, glare protection Control of color and contrast Control of font size everywhere Keyboard orientation aids

18. Accommodating Blind Users Screen Readers Full-featured Cursor-tracking, routing Dialogue focus View areas Auditory or tactile output http://www.freedomscientific.com/fs_products/software_jaws.asp http://www.webaim.org/simulations/screenreader

19. Audition (Hearing) Capabilities (best-case scenario) pitch - frequency (20 - 20,000 Hz) loudness - amplitude (30 - 100dB) location (5° source & stream separation) timbre - type of sound (lots of instruments) Often take for granted how good it is (disk whirring) Implications ?

20. Hearing uses Redundant output Email beep + icon, IM sound + popup message, etc. Output when screen not available Multimedia systems

21. Hearing problems or deafness An increasing problem? Population Phone interfaces Various technologies used: Communication aids Automated software (speech to text, etc.)

22. Touch Three main sensations handled by different types of receptors: Pressure (normal) Intense pressure (heat/pain) Temperature (hot/cold) Where important? Mouse, Other I/O, VR, surgery

23. Motor System Capabilities Range of movement, reach, speed, strength, dexterity, accuracy Workstation design, device design Often cause of errors Wrong button Double-click vs. single click Principles Feedback is important Minimize eye movement See Handbooks for data

24. Work Station Ergonomics – to Facilitate I/O

25. Large Range of Physical Impairments Complete lack of function absence of a limb paralysis – usually due to spinal injury, the higher the damage the greater the degree of paralysis Lack of strength Tremor/lack of accuracy Slowness

26. Implications Try to minimize movement and strain Alternative input devices Keyboard hardware and software Speech input Other input switches for more severe needs Eye gaze, sip and puff, etc. Acceleration techniques Word completion, macros, etc.

27. The Mind And now on to memory and cognition…

28. The “Model Human Processor” A true classic - see Card, Moran and Newell, The Psychology of Human-Computer Interaction, Erlbaum, 1983 Microprocessor-human analogue using results from experimental psychology Provides a view of the human that fits much experimental data But is a partial model Focus is on a single user interacting with some entity (computer, environment, tool) Neglects effect of other people

29. Memory Perceptual “buffers” Brief impressions Short-term (working) memory Conscious thought, calculations Long-term memory Permanent, remember everything that ever happened to us

30. LONG-TERM MEMORY SHORT-TERM (WORKING) MEMORY AUDITORY IMAGE STORE VISUAL IMAGE STORE R = Semantic D = Infinite S = Infinite R = Acoustic D = 1.5 [0.9-3.5] s S = 5 [4.4-6.2] letters R = Visual D = 200 [70-1000] ms S = 17 [7-17] letters R= Acoustic or Visual D (one chunk) = 73 [73-226] s D (3 chunks) = 7 [5-34] s S = 7 [5-9] chunks R = Representation D = Decay Time S = Size C = Cycle Time PERCEPTUAL PROCESSOR C = 100 [5-200] ms COGNITIVE PROCESSOR C = 70 [27-170] ms MOTOR PROCESSOR C = 70 [30-100] MS Eye movement (Saccade) = 230 [70-700] ms

31. Sensory Stores Very brief, but accurate representation of what was perceived Physically encoded Details decay quickly (70 - 1000 ms visual; 0.9 - 3.5 sec auditory) Limited capacity Iconic – visual 7 - 17 letters; 70 - 1000 ms decay Echoic – auditory 4 - 6 auditory; 0.9 - 3.5 sec auditory Haptic - touch Attention filters information into short term memory and beyond for more processing

32. Short Term Memory Symbolic, nonphysical acoustic or visual coding Decay 5-226 sec, rehearsal prevents decay Another task prevents rehearsal – interference Use “chunks”: 7 +- 2 units of information

33. About Chunks A chunk is a meaningful grouping of information – allows assistance from LTM 4793619049 vs. 704 687 8376 NSAFBICIANASA vs. NSA FBI CIA NASA My chunk may not be your chunk User and task dependent

34. Long-Term Memory Seemingly permanent & unlimited Access is harder, slower -> Activity helps (we have a cache) Retrieval depends on network of associations How information is perceived, understood and encoded determines likelihood of retrieval Effected by emotion, previous memory File system full

35. LT Memory Structure Episodic memory Events & experiences in serial form Helps us recall what occurred Semantic memory Structured record of facts, concepts & skills Semantic network theory Or theory of frames & scripts (like record structs)

36. Memory Characteristics Things move from STM to LTM by rehearsal & practice and by use in context Do we ever lose memory? Or just lose the link? What are effects of lack of use? We forget things due to decay and interference Similar gets in the way

37. Recognition over Recall We recognize information easier than we can recall information Examples? Implications?

38. Processes Four main processes of cognitive system: Selective Attention Learning Problem Solving Language

39. Selective Attention We can focus on one particular thing Cocktail party chit-chat Salient visual cues can facilitate selective attention Examples?

40. Learning Two types: Procedural – How to do something Declarative – Facts about something Involves Understanding concepts & rules Memorization Acquiring motor skills Automatization Tennis Driving to work  Even when don’t want to Swimming, Bike riding, Typing, Writing

41. Learning Facilitated By structure & organization By similar knowledge, as in consistency in UI design By analogy If presented in incremental units Repetition Hindered By previous knowledge Try moving from Mac to Windows => Consider user’s previous knowledge in your interface design

42. Observations Users focus on getting job done, not learning to effectively use system Users apply analogy even when it doesn’t apply Or extend it too far - which is a design problem Dragging floppy disk icon to Mac’s trash can does NOT erase the disk, it ejects disk!

43. Problem Solving Storage in LTM, then application Reasoning Deductive - Inductive - Abductive - Goal in UI design - facilitate problem solving! How?? If A, then B Generalizing from previous cases to learn about new ones Reasons from a fact to the action or state that caused it

44. Observations We are more heuristic than algorithmic We try a few quick shots rather than plan Resources simply not available We often choose suboptimal strategies for low priority problems We learn better strategies with practice

45. People Good 1. xxx 2. yyy 3. zzz Bad 1. aaa 2. bbb 3. ccc Fill in the columns - what are people good at and what are people bad at?

46. People Good Infinite capacity LTM LTM duration & complexity High-learning capability Powerful attention mechanism Powerful pattern recognition Bad Limited capacity STM Limited duration STM Unreliable access to LTM Error-prone processing Slow processing

47. Models Translating empirical evidence into theories and models that influence design. Performance measures Quantitative Time prediction Working memory constraints Competence measures Focus on certain details, others obscured More on predictive models in March

48. Context and Cognition Human information processor models all involve unaided individual In reality, people work with other people and other artifacts Other models of human cognition Situation action Activity theory Distributed cognition

49. How theories get used Descriptive power – conceptual framework for describing the world Rhetorical power – name important conceptual structures we can relate to the world Inferential power – help make inferences (maybe about new change or design…) Application – informing and guiding system design

50. Distributed Cognition (DCog) HCI Proponent: Ed Hutchins Distributed collection of interacting people and artifacts, and the communication and coordination between them

51. Distributed Cognition Cognitive System – the people, artifacts and environments Communicative pathways – the information channels Describes information flow in terms of propagation across representational state Information is transformed through different media (computers, displays, paper, heads)

52. What’s involved The distributed problem-solving that takes place The role of verbal and non-verbal behavior The various coordinating mechanisms that are used (e.g., rules, procedures) The communication that takes place as the collaborative activity progresses How knowledge is shared and accessed

53. Activity Theory Long history from cognitive science HCI proponent: Bonnie Nardi Explains human behavior in terms of our practical activity with the world Provides a framework that focuses analysis around the concept of an ‘activity’ and helps to identify tensions between the different elements of the system Two key models: one outlines what constitutes an ‘activity’; one models the mediating role of artifacts

54. Activity Theory Unit of analysis is an activity Components: subject, object, actions, operations NounHeld by subject, motivates activity “object of game” Goal-directed processes “tasks” How action is carried out

55. Individual model

56. A.T. Principles Key idea: Notion of mediation by artifacts Our work is a computer-mediated activity Starring role goes to activity In “regular” HCI, stars are person and machine Context is not “out there”. It is generated by people in activities

57. Example: call center DCog: Examine how information is transformed as it goes from caller, to employee, into the system for information, back to employee and then caller… Activity Theory Examine tensions between parts of the system such as community, tools, rules, etc.

58. Situated Action Noted proponent: Lucy Suchman Much of the theory that underlies ethnography Structuring of an activity grows out of immediacy of the situation People engage in opportunistic, flexible ways to solve problems

59. Situated Action Studies situated activity or practice Activity grows out of the particulars of a situation Improvisation is important Basic unit of analysis is “the activity of persons acting in a setting”

60. Example Need 3/4 of 2/3 of cup of cottage cheese Just has a simple measuring cup available Person solves problem by Measuring 2/3 cup Pouring out into a circle Divide into quadrants Take away one One time solution to one time problem

61. Other comments on S.A. Emergent property of moment-by-moment interactions Improvisation Detailed temporal accounts De-emphasizes rigid plans and rational problem solving

62. Comparing Models The role of goals or intentions S.A.: “retrospective reconstructions” A.T. & D.C: central Persistent structures S.A.: emphasize emergent/ contingent/ improvisatory over routine/predictable A.T.: our activity assimilates experience of humanity D.C.: much focus on transformation of artifacts over time

63. Comparing Models People and things MHP: model each as a “machine”, study the diad of H-C S.A.: qualitatively different, but mostly reactive A.T.: individual at center D.C.: both are agents, study multi-agent system

64. Some Commentary Take the reading with a grain of salt. How does this influence design?