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  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 Red629 Red-Orange596 Yellow-Orange582 Green-Yellow571 Yellow-Green538 Green510 Blue-Green491 Blue481 Violet-Blue460

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 ( ,000 Hz) loudness - amplitude ( dB) 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

Work Station Ergonomics – to Facilitate I/O

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 SHORT-TERM (WORKING) MEMORY AUDITORY IMAGE STORE VISUAL IMAGE STORE R = Semantic D = Infinite S = Infinite R = Acoustic D = 1.5 [ ] s S = 5 [ ] letters R = Visual D = 200 [ ] 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

Sensory Stores  Very brief, but accurate representation  Physically encoded  Limited capacity Iconic: 7-17 letters Echoic: 4-6 Haptic: ??  Rapid Decay Iconic: 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 “chunks” of information  Slower decay sec rehearsal prevents decay  Another task prevents rehearsal - interference

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

Implications?  Which is an implication of ? 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 previous cases to learn about new ones Abductive - Reasons from a fact to the action 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 I. Senses A. Sight B. Sound C. Touch D. Smell 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

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?

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

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!