1. Human Abilities Sensory, motor, and cognitive capabilities

2. Outline Human capabilities Senses Motor systems Information processing Memory Cognitive Processes Selective attention, learning, problem solving, language

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 Our understanding of human capabilities does change, ie Cognitive neuroscience Theories of color perception Effect of groups and situation on how we act and react

5. Human Capabilities Why do we care? Better design! Want to improve user performance Knowing the user informs the design Senses Information processing systems Physical responding

6. Senses (Our Input System) Sight, hearing, touch important for current HCI Smell, taste ??? Abilities and limitations affect design

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 About 9 % of males are red-green colorblind! 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. Color Surround

12. Effect of Colored Text on Colored Background Black text on white Gray text on white Yellow text on white Light yellow text on white Green text on white Light green text on white Blue text on white Pale blue text on white Dark red text on white Red text on white Rose text on white

13. Effect of Colored Text on Colored Background Black text on red Gray text on red Yellow text on red Light yellow text on red Green text on red Light green text on red Blue text on red Pale blue text on red Dark red text on red Red text on red Rose text on red

14. Effect of Colored Text on Colored Background Black text on dark blue Gray text on dark blue Yellow text on dark blue Light yellow text on dark blue Green text on dark blue Light green text on dark blue Blue text on dark blue Pale blue text on dark blue Dark red text on dark blue Red text on dark blue Rose text on dark blue

15. 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 ?

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

17. Smell Joseph Kaye, “Making scents: aromatic output for HCI” ACM Interactions Volume 10, Number 1 (2004), Pages 48-61 Solenoid-controlled scent bottles

18. Motor System (Our Output 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

19. Work Station Ergonomics – to Facilitate I/O

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

21. 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

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

23. 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

24. Perceptual or Sensory Memory 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 (7 - 17 letters visual; 4 - 6 auditory)

25. Sensory Stores 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 Processors – interpret signal into semantically meaningful Pattern recognition, language, etc.

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

27. 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

28. 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 File system full

29. LT Memory Structure Episodic memory Events & experiences in serial form Helps us recall what occurred Semantic memory Structured record of facts, concepts & skills One theory says it’s like a network Another uses frames & scripts (like record structs)

30. 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

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

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

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

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

35. 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

36. 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!

37. 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

38. 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

39. Implications Allow flexible shortcuts Forcing plans will bore user Have active rather than passive help Recognize waste

40. Language Rule-based How do you make plurals? Productive We make up sentences Key-word and positional Patterns Should systems have natural language interfaces? Stay tuned

41. Recap I. Senses A. Sight B. Sound C. Touch D. Smell II. Information processing A. Perceptual B. Cognitive 1. Memory a. Short term b. Medium term c. Long term 2. Processes a. Selective attention b. Learning c. Problem solving d. Language III. Motor system A. Hand movement B. Workstation Layout

42. 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?

43. 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

44. Class Discussion: Model Human Processor What are the three major subsystems and their functions? What does it mean to say that certain subprocessors have “variable rates?” What are some of the other assumptions underlying the MHP model? How good is the model?

45. Scenarios Make sure it is a story with Actors (at least one person) Actions (not just the context) Good focus on the negative Try to follow through with what the person does