Human Abilities and Models Sensory and cognitive abilities and models, models of human performance
Outline n Human capabilities and disabilities n Senses n Motor systems n Memory n Cognitive Processes n Selective attention, learning, problem solving, language n Contextual models
Typical Person n Do we really have limited memory capacity?
Basic Human Capabilities n Do not change very rapidly n Not like Moore’s law! n Have limits, which are important to understand n Why do we care? n Better design! n Want to improve user performance n Universal design – designing for all people, including those with disabilities
But… we’re all disabled sometimes n Environment n Fatigue n Injury n Aging n Changing role of information technology
Usable Senses The 5 senses (sight, sound, touch, taste and smell) are used by us every day n n 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? n ideally, yes n practically – no We can use • sight • sound • touch (sometimes) We cannot (yet) use • taste • smell
Vision Fundamentals n Retina has 6. 5 M cones (color vision), mostly at fovea (1/3)˚ n About 150, 000 cones per square millimeter n Fewer blue sensing cones than red and green at fovea n 100 M rods (night vision), spread over retina, none at fovea n Adaptation n Switching between dark and light causes fatigue n
Vision implications (more to come in visual design) n Color n Distinguishable hues n optical illusions n Acuity n Determines smallest size we can see n Less for blue and yellow than for red and green
Color/Intensity Discrimination n The 9 hues most people can identify are: Color Red-Orange Yellow-Orange Green-Yellow-Green Blue-Green Blue Violet-Blue Wavelength 629 596 582 571 538 510 491 481 460
Color Surround Effect n Our perception of a color is affected by the surrounding color
Vision Difficulties n Color blindness About 9 % of males are red-green colorblind! n See http: //colorlab. wickline. org/colorblind/colorlab/ n Low-vision n The vast majority of visually disabled people have some sight n Blindness n Rely on other senses to receive information n Specialized hardware and software n n n Screen readers Braille printers, etc.
Myopia and Hypermetropia n Myopia n (short-sighted) Hypermetropia (far-sighted)
Macular degeneration
Diabetic retinopathy
Cataracts
Tunnel vision
Accommodating Partial Sight n Large monitor, high resolution, glare protection n Control of color and contrast n Control of font size everywhere n Keyboard orientation aids
Accommodating Blind Users n Screen Readers n Full-featured n Cursor-tracking, routing n Dialogue focus n View areas n Auditory or tactile output http: //www. freedomscientific. com/fs_products/software_jaws. asp http: //www. webaim. org/simulations/screenreader
Audition (Hearing) n Capabilities (best-case scenario) n pitch - frequency (20 - 20, 000 Hz) n loudness - amplitude (30 - 100 d. B) n location (5° source & stream separation) n timbre - type of sound (lots of instruments) n Often take for granted how good it is (disk whirring) n Implications ?
Hearing uses n Redundant output n Email beep + icon, IM sound + popup message, etc. n Output when screen not available n Multimedia systems
Hearing problems or deafness n An increasing problem? n Population n Phone interfaces n Various technologies used: n Communication aids n Automated software (speech to text, etc. )
Touch n Three main sensations handled by different types of receptors: n n n Pressure (normal) Intense pressure (heat/pain) Temperature (hot/cold) n Where important? n Mouse, Other I/O, VR, surgery
Motor System n Capabilities n Range of movement, reach, speed, strength, dexterity, accuracy n Workstation design, device design n Often cause of errors n Wrong button n Double-click vs. single click n Principles n Feedback is important n Minimize eye movement n See Handbooks for data
Work Station Ergonomics – to Facilitate I/O
Large Range of Physical Impairments n. Complete lack of function n absence of a limb n paralysis – usually due to spinal injury, the higher the damage the greater the degree of paralysis n. Lack of strength n. Tremor/lack of accuracy n. Slowness
Implications n Try to minimize movement and strain n Alternative input devices n Keyboard hardware and software n Speech input n Other input switches for more severe needs n n Eye gaze, sip and puff, etc. Acceleration techniques n Word completion, macros, etc.
The Mind n And now on to memory and cognition…
The “Model Human Processor” n A true classic - see Card, Moran and Newell, The Psychology of Human-Computer Interaction, Erlbaum, 1983 n n n Microprocessor-human analogue using results from experimental psychology Provides a view of the human that fits much experimental data But is a partial model n Focus is on a single user interacting with some entity (computer, environment, tool) n Neglects effect of other people
Memory n Perceptual “buffers” n Brief impressions n Short-term (working) memory n Conscious thought, calculations n Long-term memory n Permanent, remember everything that ever happened to us
LONG-TERM MEMORY R = Semantic D = Infinite SHORT-TERM (WORKING) MEMORY VISUAL IMAGE STORE R = Visual D = 200 [70 -1000] ms S = 17 [7 -17] letters AUDITORY IMAGE STORE R = Acoustic D = 1. 5 [0. 9 -3. 5] s S = 5 [4. 4 -6. 2] letters R= Acoustic or Visual D (one chunk) = 73 [73 -226] s D (3 chunks) = 7 [5 -34] s S = 7 [5 -9] chunks PERCEPTUAL PROCESSOR COGNITIVE PROCESSOR MOTOR PROCESSOR C = 100 [5 -200] ms C = 70 [27 -170] ms C = 70 [30 -100] MS R = Representation D = Decay Time S = Size C = Cycle Time Eye movement (Saccade) = 230 [70 -700] ms
Sensory Stores n Very brief, but accurate representation of what was perceived n Physically encoded n Details decay quickly (70 - 1000 ms visual; 0. 9 - 3. 5 sec auditory) n Limited capacity n n n Iconic – visual n 7 - 17 letters; 70 - 1000 ms decay Echoic – auditory n 4 - 6 auditory; 0. 9 - 3. 5 sec auditory Haptic - touch n Attention filters information into short term memory and beyond for more processing
Short Term Memory n Symbolic, nonphysical acoustic or visual coding n Decay 5 -226 sec, rehearsal prevents decay n Another task prevents rehearsal – interference n Use “chunks”: 7 +- 2 units of information
About Chunks n A chunk is a meaningful grouping of information – allows assistance from LTM n 4793619049 vs. 704 687 8376 n NSAFBICIANASA vs. NSA FBI CIA NASA n My chunk may not be your chunk n User and task dependent
Long-Term Memory n Seemingly permanent & unlimited n Access is harder, slower n -> Activity helps (we have a cache) n Retrieval depends on network of associations n How information is perceived, understood and encoded determines likelihood of retrieval n Effected by emotion, previous memory File system full
LT Memory Structure n Episodic memory n Events & experiences in serial form n Helps us recall what occurred n Semantic memory n Structured record of facts, concepts & skills n n Semantic network theory Or theory of frames & scripts (like record structs)
Memory Characteristics n Things move from STM to LTM by rehearsal & practice and by use in context n n Do we ever lose memory? Or just lose the link? What are effects of lack of use? n We forget things due to decay and interference n Similar gets in the way
Recognition over Recall n We recognize information easier than we can recall information n Examples? n Implications?
Processes n Four main processes of cognitive system: n Selective Attention n Learning n Problem Solving n Language
Selective Attention n We can focus on one particular thing n Cocktail party chit-chat n Salient visual cues can facilitate selective attention n Examples?
Learning n Two types: n Procedural – How to do something n Declarative – Facts about something n Involves n Understanding concepts & rules n Memorization n Acquiring motor skills n Automatization n Tennis n Driving to work § Even when don’t want to n Swimming, Bike riding, Typing, Writing
Learning n Facilitated n By structure & organization n By similar knowledge, as in consistency in UI design n By analogy n If presented in incremental units n Repetition n Hindered n By previous knowledge n Try moving from Mac to Windows => Consider user’s previous knowledge in your interface design
Observations n Users focus on getting job done, not learning to effectively use system n Users apply analogy even when it doesn’t apply n Or extend it too far - which is a design problem n Dragging floppy disk icon to Mac’s trash can does NOT erase the disk, it ejects disk!
Problem Solving n Storage in LTM, then application n Reasoning n Deductive - If A, then B n Inductive - Generalizing from previous cases to learn about new ones n Abductive - Reasons from a fact to the action or state that caused it n Goal in UI design - facilitate problem solving! n How? ?
Observations n We are more heuristic than algorithmic n We try a few quick shots rather than plan n Resources simply not available n We often choose suboptimal strategies for low priority problems n We learn better strategies with practice
People n Good 1. 2. 3. xxx yyy zzz n Bad 1. 2. 3. aaa bbb ccc Fill in the columns what are people good at and what are people bad at?
People n Good n Infinite capacity LTM n LTM duration & complexity n High-learning capability n Powerful attention mechanism n Powerful pattern recognition n Bad n Limited capacity STM n Limited duration STM n Unreliable access to LTM n Error-prone processing n Slow processing
Models n Translating empirical evidence into theories and models that influence design. n Performance measures n n n Quantitative Time prediction Working memory constraints n Competence measures n Focus on certain details, others obscured n More on predictive models in March
Context and Cognition n Human information processor models all involve unaided individual n In reality, people work with other people and other artifacts n Other models of human cognition Situation action n Activity theory n Distributed cognition n
How theories get used n Descriptive power – conceptual framework for describing the world n Rhetorical power – name important conceptual structures we can relate to the world n Inferential power – help make inferences (maybe about new change or design…) n Application – informing and guiding system design
Distributed Cognition (DCog) n HCI Proponent: Ed Hutchins n Distributed collection of interacting people and artifacts, and the communication and coordination between them
Distributed Cognition n Cognitive System – the people, artifacts and environments n Communicative pathways – the information channels n Describes information flow in terms of propagation across representational state n Information is transformed through different media (computers, displays, paper, heads)
What’s involved n The distributed problem-solving that takes place n The role of verbal and non-verbal behavior n The various coordinating mechanisms that are used (e. g. , rules, procedures) n The communication that takes place as the collaborative activity progresses n How knowledge is shared and accessed
Activity Theory n Long history from cognitive science n HCI proponent: Bonnie Nardi n Explains human behavior in terms of our practical activity with the world n Provides a framework that focuses analysis around the concept of an ‘activity’ and helps to identify tensions between the different elements of the system n Two key models: one outlines what constitutes an ‘activity’; one models the mediating role of artifacts
Activity Theory n Unit of analysis is an activity n Components: subject, object, actions, operations Noun Held by subject, Goal-directed motivates activity processes “object of game” “tasks” How action is carried out
Individual model
A. T. Principles n Key idea: Notion of mediation by artifacts n Our work is a computer-mediated activity n Starring role goes to activity n In “regular” HCI, stars are person and machine n Context is not “out there”. It is generated by people in activities
Example: call center n DCog: n Examine how information is transformed as it goes from caller, to employee, into the system for information, back to employee and then caller… n Activity Theory n Examine tensions between parts of the system such as community, tools, rules, etc.
Situated Action n Noted proponent: Lucy Suchman n Much of theory that underlies ethnography n Structuring of an activity grows out of immediacy of the situation n People engage in opportunistic, flexible ways to solve problems
Situated Action n Studies situated activity or practice n Activity grows out of the particulars of a situation n Improvisation is important n Basic unit of analysis is “the activity of persons acting in a setting”
Example n Need 3/4 of 2/3 of cup of cottage cheese n Just has a simple measuring cup available n Person solves problem by n Measuring 2/3 cup n Pouring out into a circle n Divide into quadrants n Take away one n One time solution to one time problem
Other comments on S. A. n Emergent property of moment-by-moment interactions n Improvisation n Detailed temporal accounts n De-emphasizes rigid plans and rational problem solving
Comparing Models n The role of goals or intentions n S. A. : “retrospective reconstructions” n A. T. & D. C: central n Persistent structures n S. A. : emphasize emergent/ contingent/ improvisatory over routine/predictable n A. T. : our activity assimilates experience of humanity n D. C. : much focus on transformation of artifacts over time
Comparing Models n People and things n MHP: model each as a “machine”, study the diad of H-C n S. A. : qualitatively different, but mostly reactive n A. T. : individual at center n D. C. : both are agents, study multi-agent system
Some Commentary n Take the reading with a grain of salt. n How does this influence design?
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