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Human Abilities and Models. Sensory and cognitive abilities and models, models of human performance. Outline. Human capabilities and disabilities Senses Motor systems Memory Cognitive Processes Selective attention, learning, problem solving, language Contextual models. Typical Person.
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Human Abilities and Models Sensory and cognitive abilities and models, models of human performance
Outline • Human capabilities and disabilities • Senses • Motor systems • Memory • Cognitive Processes • Selective attention, learning, problem solving, language • Contextual models
Typical Person • Do we really have limited memory capacity?
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
But… we’re all disabled sometimes • Environment • Fatigue • Injury • Aging • Changing role of information technology
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
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
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
Color/Intensity Discrimination • The 9 hues most people can identify are: ColorWavelength Red 629 Red-Orange 596 Yellow-Orange 582 Green-Yellow 571 Yellow-Green 538 Green 510 Blue-Green 491 Blue 481 Violet-Blue 460
Color Surround Effect • Our perception of a color is affected by the surrounding color
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.
Myopia and Hypermetropia • Myopia Hypermetropia • (short-sighted) (far-sighted)
Accommodating Partial Sight • Large monitor, high resolution, glare protection • Control of color and contrast • Control of font size everywhere • Keyboard orientation aids
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
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 ?
Hearing uses • Redundant output • Email beep + icon, IM sound + popup message, etc. • Output when screen not available • Multimedia systems
Hearing problems or deafness • An increasing problem? • Population • Phone interfaces • Various technologies used: • Communication aids • Automated software (speech to text, etc.)
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
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
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
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.
The Mind • And now on to memory and cognition…
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
Memory • Perceptual “buffers” • Brief impressions • Short-term (working) memory • Conscious thought, calculations • Long-term memory • Permanent, remember everything that ever happened to us
LONG-TERM MEMORY R = Semantic D = Infinite S = Infinite SHORT-TERM (WORKING) MEMORY VISUAL IMAGE STORE AUDITORY IMAGE STORE R= Acoustic or Visual D (one chunk) = 73 [73-226] s D (3 chunks) = 7 [5-34] s S = 7 [5-9] chunks R = Visual D = 200 [70-1000] ms S = 17 [7-17] letters R = Acoustic D = 1.5 [0.9-3.5] s S = 5 [4.4-6.2] letters PERCEPTUAL PROCESSOR C = 100 [5-200] ms COGNITIVE PROCESSOR C = 70 [27-170] ms MOTOR PROCESSOR C = 70 [30-100] MS R = Representation D = Decay Time S = Size C = Cycle Time Eye movement (Saccade) = 230 [70-700] ms
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
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
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
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
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)
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
Recognition over Recall • We recognize information easier than we can recall information • Examples? • Implications?
Processes • Four main processes of cognitive system: • Selective Attention • Learning • Problem Solving • Language
Selective Attention • We can focus on one particular thing • Cocktail party chit-chat • Salient visual cues can facilitate selective attention • Examples?
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
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
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!
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 previouscases to learn about new ones Reasons from a fact to theaction or state that caused it
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
Good xxx yyy zzz People • Bad • aaa • bbb • ccc Fill in the columns - what are people good at and what are people bad at?
Good Infinite capacity LTM LTM duration & complexity High-learning capability Powerful attention mechanism Powerful pattern recognition People • Bad • Limited capacity STM • Limited duration STM • Unreliable access to LTM • Error-prone processing • Slow processing
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
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
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
Distributed Cognition (DCog) • HCI Proponent: Ed Hutchins • Distributed collection of interacting people and artifacts, and the communication and coordination between them