Human Abilities Sensory, motor, and cognitive capabilities
Outline • Human capabilities • Senses • Motor systems • Information processing • Memory • Cognitive Processes • Selective attention, learning, problem solving, language • Predictive Models -> next lecture
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 • Our abilities to not change, but our understanding of them does • Why do we care? • Better design! • Want to improve user performance • Universal design – design for everyone, including those with disabilities • We’ll come back to this later in the semester…
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 • About 9 % of males are red-green colorblind! • See http://colorlab.wickline.org/colorblind/colorlab/ • 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
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
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 ?
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 (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
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 • Physically encoded • Limited capacity • Iconic: 7-17 letters • Echoic: 4-6 • Haptic: ?? • Rapid Decay • Iconic: 70-1000 ms • Echoic: 0.9 – 3.5 sec • Attention filters information into short term memory and beyond for more processing • Perceptual Processor – interpret signal into semantically meaningful • Pattern recognition, language, etc.
Short Term Memory • Symbolic, nonphysical acoustic or visual coding • Somewhat limited capacity • 7 +- 2 “chunks” of information • Slower decay • 5-226 sec • rehearsal prevents decay • Another task prevents rehearsal - interference
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
Implications? • Which is an implication of 7 +- 2? • Use 5-9 items on a menu • Display 5-9 icons on a task bar • No more than 7 tabs on a window • 5-9 items in a list
Long-Term Memory • Semantic storage • 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
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)
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 • Automotization • 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 – If A then B • Inductive - Generalizing from previouscases to learn about new ones • Abductive - Reasons from a fact to theaction or state that caused it • Goal in UI design - facilitate problem solving! • How??
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
Implications • Allow flexible shortcuts • Forcing plans will bore user • Have active rather than passive help • Recognize waste
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
Recap II. Information processing A. Perceptual B. Cognitive 1. Memory a. Short term b. Long term 2. Processes a. Selective attention b. Learning c. Problem solving d. Language I. Senses A. Sight B. Sound C. Touch D. Smell
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
Class Discussion:Model Human Processor • How good is the model? • What kinds of assumptions are they making?
Assignment: 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
Next Assignment: HTA • Current activity that relates to your project topic • Either create diagram and upload the file to the Swiki • Or use the numbered outline approach • Don’t forget those plans!