Human Abilities: Cognition

Human Abilities: Cognition
James Landay John Kelleher

Plain English campaign!

Outline Human visual system Guidelines for design
Models of human performance (MHP) Memory

Models of the User Model Human Processor Our Model Cognitive System
Perceptual System Memory I/O Motor System CPU

Human I/O Channels Input via the senses Output via motor control Sight
Hearing Touch Taste Smell Output via motor control Limbs (feet?) Fingers Eyes Head Voice

Why Model Human Performance?
To test understanding To predict influence of new technology

The Model Human Processor
Developed by Card, Moran, & Newell (’83) based on empirical data Long-term Memory Working Memory Visual Image Store Auditory Image Cognitive Processor Motor Eyes Ears Fingers, etc. sensory buffers Perceptual Processor

Model Human Processor (Card, Moran & Newell)

Model Human Processor Components
Cycle times Decay Rates Storage Capacities Coding/Representation Schemes

Perceptual (Sensory) Memories
Area of memory that deals with information from the senses Perceptual memories are highly volatile information stores Information flows from perceptual (sensory) memories into Working Memory Perceptual memories decay almost immediately and are replaced by new, incoming information Selection of stimuli governed by level of arousal

What is This?

Parameters of Perceptual Memories
Visual (Iconic) Memory Coding Scheme – Physical analogs Capacity – ~17 letters Decay Rate – ~200ms Auditory (Echoic) Memory Capacity – ~5 letters Decay Rate – ~1500 ms Buffers for stimuli

Perceptual Processor The speed of the perceptual processor is about ~100ms per cycle Light blinks appearing within 100ms look like a single brighter light e.g. frames of a film seen as continuous fluid scene reflects some processing by sensory processor. Light blinks in two locations within 100ms look like motion of a single light Auditory clicks occurring within 100ms sound like one louder tone Also, sensory memory for hearing more durable than others Multiple taps occurring within 100ms feel like one tap of greater pressure

Working Memory (Short-term Memory)
Working Memory is a temporary information store. Working Memory receives information from Perceptual Memories and LTM Working Memory can influence LTM Information in Working Memory is often recoded e.g. Visual information is rehearsed as auditory Chunking is already happening People have some control over Working Memory Rehearsal Attention Sensory memory Attention Working Rehearsal Long-term

Memory Working memory (short term) Chunking
small capacity (7 ± 2 “chunks”) vs. (617) AIBIBMEMC vs. AIB IBM EMC Chunking Grouping together information into sections that make sense to the individual and seen as entities by that individual E.g. master chess players (but only for legal positions) rapid access (~ 70ms) & decay (~200 ms) pass to LTM after a few seconds

Chunking 1 chunk Recoded to image 3 chunks Recoded to words
B I G O L D M A N BIG OLD MAN x x x 1 chunk Recoded to image 3 chunks Recoded to words 9 chunks Recoded to letters Perceptual memory

Primacy and Recency Effects
List 1 List 2 List 3 Barrier Babies File Firearms Sofa Heart Scarf Lobby Scarecrow Newspaper Clock Stylus Sea-shell Polish Maggot Tomato Lintels Rug Apologies Dog Flea Table Dolls-house Ball-pen Plant Oasis Jamboree Chemist Festival Neptune Identity Gnat Magnum Percolator Curtains Paper-clip Saucer Income Typist Tiles Precinct Subway Directory Argument Accident

Primacy & Recency Effect
Free recall Recalling lists in any order Primacy effect Tendency for first words on list to be commonly recalled Recency effect Tendency for last words on list to be commonly recalled

Fun with Working Memory
HEC ATR ANU PTH ETR EET

Interference affects recency
List 1 List 2 Then do… Aubergine Rescue 1 Chickenpox Gravestone +6 Elephant Flower -4 Telephone Fountain +9 Pendant Statue -2 Egg Fool +8 Melancholy Aphid -9 Cheese Surprise -6 Mug Printer Nymph Cenotaph Dinghy Dog basket Tray Magnet Mole Lawn Tram Pram Macabre Sandwich

Memory Extent to which new material can be remembered depends on its meaningfulness Levels (Depth) of processing theory (Craik & Lockhart, 1972) Info processed at different levels e.g., processing physical features of a word such as its sound Deep, semantical analysis Depth of processing determines how well remembered Elaborative (effortful process) vs. maintenance rehearsal Closure Feeling of ‘relief’ when task successfully completed E.g. successful logon Important to permit processes to be chunked in memory E.g. avoid traversing between windows within an application

Depth of Processing (shallow)
flame patch sonic bless avarice pears spade bliss forth peels speed avoid freak pints rare blush slow pluck

Depth of Processing (deep)
spoon shares glass ports spray boots goose prize steam runner grass pint stink bride green queen story brown

Memory Factors that determine meaningfulness
Familiarity of an item, and the frequency with which a word occurs in everyday language Familiar: Door, read, stop Unfamiliar: compile, substitute, scan It’s associated imagery, the ability with which the word can elicit images in one’s mind Ride, sleep, eat Begin, increase, evaluate Information best recalled if in situ E.g. Diver education (Baddeley) The study compared the ability of novice divers to apply decompression tables having learnt how to use them in either the same or a different environment. Those subjects who had learnt to use the tables in a different environment (i.e. had learnt on dry land and were tested underwater or vice-versa) performed on average 64 per cent worse than those who had the same environment for both learning and test. This effect could not be ascribed to the disruption brought about by changing environments. The results show that contextual effects on memory extend beyond the recall of word lists (Godden and Baddeley, 1975) to the ability to implement potentially important instructions

Improving memory Method of Loci Peg-word method Creating a narrative
Visualising familiar route & associated items at particular locations long route Peg-word method Associate items with rhyming words & numbers Creating a narrative Create story or song linking concepts together Creating acronyms e.g. A.B.C. of First Aid

Implications for UI design
Items that need to be remembered at the interface should be as meaningful as possible Problems with command line interfaces e.g., command names and icons should be selected according to meaningfulness cp vs. copy Words that represent visible objects easiest to recall Memory best facilitated by relaxed user Ask only relevant material Or provide user with reason for action Asking for non-sensible information

Peg Word Memory Aid 1 bun 2 shoe 3 tree 4 door 5 hive 6 sticks
7 heaven 8 gate 9 wine 10 hen

Memory Factors Total time hypothesis Distribution of Practice Effect
Listen The engines roared above the noise of the crowd. Even in the blistering heat people rose to their feet and waved their hands in excitement. The flag fell and they were off. Within seconds the car had pulled away from the pack and was careering round the bend at a desperate pace. Its wheels momentarily left the ground as it cornered. Coming down the straight the sun glinted on its shimmering paint. The driver gripped the wheel with fierce concentration. Sweat lay in fine drops on its brow. People prone to embellishment and ‘localisation’ of facts.

Long-Term Memory (LTM)
Long-term memory stores everything that we “know” -- facts, experience, knowledge, procedural rules of behavior. LTM has huge capacity. LTM has a relatively slow access compared to short-term memory. ‘activation’ is process of recall to WM Only encode the important information Forgetting also occurs slowly. Causes for forgetting 1) Never stored; encoding failed 2) Gone from storage; storage failed (??) 3) Can’t get out of storage; retrieval failed Interference model of forgetting one item inhibits the retrieval of another proactive interference (3) retroactive interference (3 & 2)

Pennies Example

Long-term Memory Long-term memory works by semantics and by association. SHEEPDOG HOUND Is a ANIMAL DOG moves breathes barks Four legs has tail eats

Parameters of LTM Semantic network (encoded in terms of meaning and relationships). Related associations, images, and past experiences How knowledge is encoded makes a difference in how knowledge is recalled Recognition is much easier than recall (DOS prompt vs. Mac user interface) Coding Scheme – Semantic Capacity – Unlimited Decay Rate – None However, recall from LTM is affected by encoding specificity and retrieval cues

Encoding Specificity “Specific encoding operations performed on what is perceived determine what is stored, and what is stored determines what retrieval cues are effective in providing access to what is stored.” -- Card, Moran, & Newell (1983) This is a fancy way of saying that the encoding context matters

Discrimination Principle
“The difficulty of memory retrieval is determined by the candidates that exist in the memory relative to the retrieval cues.” -- Card, Moran, & Newell (1983)

Cognitive Processor “The recognize-act cycle…is the basic quantum of cognitive processing.” (CMN, 1983) In each cycle, the contents of Working Memory activate something in LTM which in turn modifies the contents of Working Memory Cycle time is ~70ms

Motor Processor Draw parallel lines (approx. 4cm apart)
For a duration of 5 seconds… Draw a zig-zag line back and forth between the lines working left to right The basic motor cycle time is ~70ms Move pen back and forth between two lines ~71 reversals in 5 sec, or ~70ms/reversal forgetting anything?

Putting It All Together
True reaction time 1 perceptual cycle + 1 cognitive cycle + 1 motor cycle 100ms+70ms+70ms = 240ms Some studies include additional cognitive step Raises total by 70ms to 340ms

Principles of Operation (cont.)
Fitts’ Law moving hand is a series of microcorrections correction takes Tp + Tc + Tm = 240 msec time Tpos to move the hand to target size S which is distance D away is given by: Tpos = a + b log2 (D/S + 1) summary time to move the hand depends only on the relative precision required

Fitts’ Law Example Which will be faster on average? Pop-up Linear Menu
Today Sunday Monday Tuesday Wednesday Thursday Friday Saturday Pop-up Linear Menu Pop-up Pie Menu Which will be faster on average? pie menu (bigger targets & less distance)

Perception Stimuli that occur within one PP cycle fuse into a single concept frame rate needed for movies to look real? time for 1 frame < Tp (100 msec) -> 10 frame/sec. Perceptual causality two distinct stimuli can fuse if the first event appears to cause the other events must occur in the same cycle

Perceptual Causality How soon must red ball move after cue ball collides with it? must move in < Tp (100 msec)

What is missing from MHP?
Haptic memory for touch Moving from sensory memory to WM attention filters stimuli & passes to WM Moving from WM to LTM elaboration

Cognitive Processes Controlled Automatic
limited capacity; require attention and conscious control easier to change Automatic Activities we carry out that have become automated Reading, writing, speaking in native language… (others?) We don’t have to attend to (think about) what we are doing.

Automatic Processing Characteristics
The more we practice, the more our performance improves to the point that we become skilled, and performance is automatic Characteristics fast, demanding minimal attention, therefore doesn’t interfere with other activities unavailable to consciousness hard to change once learned

Effect on UI design decisions
Interactions that have become automatic are difficult to unlearn Microsoft’s approach to WordPerfect domination Consistency across versions, tools can help avoid this problem Microsoft Office critical mass of usage stiffles StarOffice

Stroop Effect Example of automatic behaviour Volunteer
Start saying colors you see in list of words when slide comes up as fast as you can Say “done” when finished Everyone else time it…

Say the colour of these words
Paper Home Back Schedule Page Change

Simple Experiment Do it again Say “done” when finished

Now do it again… Blue Red Black White Green Yellow

Importance of Context Bottom-up perception uses features of stimulus
Top-down perception uses context (and prior knowledge) Temporal (for hearing) – what we heard before or after stimulus Spatial (for visual) – what’s around the stimulus (as below) draws on long-term memory

Gestalt Laws of Grouping
German Psychologists Primary purpose of visual system is recognition of objects from basic visual elements Objects seen as more than a sum of the parts When elements are arranged in groups that define an object, we tend to see the object and not the elements. e.g. ascii art

Gestalt Principles Similarity Proximity Similarity Closure Continuity
Organizing principles which enable us to perceive the patterns of stimuli as meaningful wholes: Proximity: dots appear as groups rather than as a random cluster of elements Similarity: tendency for elements of the same shape or design or color to be seen as belonging together. Closure: missing parts of the figure are filled in to complete it, so it appears as a whole circle Continuity: stimulus appears to be made of two lines of dots, traversing each other, rather than a random set of dots Symmetry: regions bounded by symmetrical borders tend to be perceived as coherent figures. Continuity Symmetry

Law of Proximity Things that are relatively close to one another tend to be grouped together.

Laws of Similarity Items that look similar will be seen as parts of the same form

Law of good continuation
Objects arranged in either a straight line or a smooth curve tend to be seen as a unit.

Law of Closure Innate tendency to perceive incomplete objects as complete and to close or fill gaps and to perceive asymmetric stimuli as symmetric

Law of common fate The law of common fate leads us to group together objects that move in the same direction. In the following illustration, imagine that three of the balls are moving in one direction, and two of the balls are moving in the opposite direction. If you saw these in actual motion, you would mentally group the balls that moved in the same direction. Because of this principle, we often see flocks of birds or schools of fish as one unit.

Attention “Everyone knows what attention is. It is the taking possession of mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought … It requires withdrawal from some things in order to deal effectively with others.” W. James, 1890

“cocktail party phenomenon”
Ability to focus on one activity, while tuning out others can be distracted from one task if attention called to another

Attention Can design interfaces to help users find information they need Can structure interface so it is easy to navigate Not too much information, nor too little Rather than arbitrarily presenting information: use groupings order in meaningful way See Gestalt laws of perceptual grouping

Attention Manner in which we deploy our attention has a tremendous bearing on how effectively we can interact with a system Focused attention Ability to attend to one event from what amounts to a mass of competing stimuli in the environment Divided attention Ability to attend to more than one stimuli at a time Cocktail party phenomenon Voluntary or involuntary

Implications for Design
Users are prone to distraction On returning to suspended activity: May forget where they left off May forget whether they completed the task or not Forgetting to put salt French fries, or doing it twice Answer: cognitive aids Reminders or external representations intended to gain attention at a time relevant to the task that needs to be performed. E.g., status area indicating task status, coffee cup on flaps

Attention Other techniques for presenting information to guide attention Spatial and temporal cues Example Color Alerting techniques Flashing and reverse video Audio warnings

Attention Windows are a useful way to partition the screen into discrete or overlapping sections enable different types of information to be separated, provides meaningful groupings e.g., word processor Text area Footnote area Command area

Info which needs immediate attention should always be displayed in a prominent place (error and warning messages)

Less urgent info should be allocated to a less prominent but specific areas of the screen so that the user will know where to look when this information is required.

Information that is not needed very often should not be displayed but should be made available on request.

Goals of Representation Aiding
Turn a cognitive task into a perceptual task. Offload human working memory onto an external representation. Map relevant constraints in the domain onto relevant representational properties. Encourage people to develop a “correct” mental model

You have to understand the person’s task!! You have to understand the domain! People have cognitive constraints and abilities The domain imposes constraints Map those together into a design that represents domain constraints in a way that people can best perceive/understand.

Ventilator Management Example
Practitioners: Intensive Care Unit specialists Task: To evaluate whether a patient is recovering his/her own breathing over time Ventilator vs. Patient: Rate of breathing, depth of breathing

Today’s displays Typical process control displays with tables and tables of “Label:Value” parameters Every variable that’s measured by the patient is displayed on the screen, (single sensor single indicator) e.g.: Ventilator Patient Rate of breathing: 10 Rate of breathing: 2 Depth of breathing: 5 Depth of breathing: 6 Difficult to get “status at a glance”, to judge whether patient is improving or not.

Novel Display (Volume Rectangles)
Ventilator Patient rate volume (Cole and Stewart, 1994)

A series of volume rectangles
Ventilator Patient at time t1 Ventilator Patient at time t21 The patient is clearly doing more of his/her own breathing over time.

Evaluation of Novel Display
Physicians had perfect performance in judging whether patients were getting better or worse over time. Furthermore, the physicians’ judgments were significantly faster using the novel volume rectangle display than using the familiar table of numbers currently used in practice.

Recognition over Recall
info reproduced from memory e.g., command name & semantics Recognition presentation of info provides knowledge that info has been seen before e.g., command in menu reminds you of semantics easier because of cues to retrieval cue can be anything related to item or situation where it was learned example: giving hints other examples in software? icons, labels, menu names, etc.

Knowledge in the Head and in the World
Knowledge in the world is the information in the environment Knowledge in the head is the information that is stored in memory Most of the time we need to combine the two types knowledge to operate things.

Knowledge in the World/Head

Because ... Not all of the knowledge required for precise behavior has to be in the head partly in the head partly in the world partly in the constraints E.g. clipboard and ‘spike’

We can recognize material far more easily than we can recall it.
Also because ... We can recognize material far more easily than we can recall it. Knowledge in the world lets people recognize facts or things. E.g. road signs Knowledge in the head requires recall.

AIB 24-Hour Online Banking
User logs on to: Check balances Move funds Cancel cheques AIB offers TransactOnline to: Provide one-time credit card numbers tied to user’s account

Opening Logon Screen

Further Validation Screen

TransactOnline SignOn

Further Reading Vision and Cognition
Books The Psychology Of Human-Computer Interaction, by Card, Moran, & Newell, Erlbaum, 1983 Human-Computer Interaction, by Dix, Finlay, Abowd, and Beale, 1998. Perception, Irvin Rock, 1995. Articles “Using Color Effectively (or Peacocks Can't Fly)” by Lawrence J. Najjar, IBM TR , January, 1990,

Extra Slides

Vision (1/3) Two aspects: physical receptor & subsequent perception processing Photoreceptors: Rods (120 m., light sensitive, can be saturated, concentrated on edges of retina, poor visual acuity). Cones (6 m., less light sensitive, colour perceptors, concentrated on fovea, blind spot). Ganglion cells specialised nerve cells X-cells (fovea centred, pattern detection) Y-cells (distributed on retina, movement detection) Size & Depth Perception Visual angle (larger angle at same distance implies larger object) Visual acuity (fine detail perception) Law of size constancy relies on cues - overlapping objects, size and height of object, familiarity with object.

Vision (2/3) Brightness Colour Visual Processing
Subjective quantity; affected by luminance; contrast visual system adjusts to perceive in differing lighting; rods/cones visual acuity increases with luminance as does ‘flicker’ Colour 3 components (hue, intensity, saturation) Hue determined by wavelength Blues short, greens medium and reds long wavelength. Intensity is brightness of colour Saturation is amount of whiteness in the colour (‘washed-out’ affect) 3 types of cones sensitive to RGB (fewest cones for blue) colour blindness Visual Processing Movement of retina & changes in luminance are perceived as constant Ability to interpret and anticipate images is vital - easily fooled, however. Muller-Lyer illusion, Ponzo illusion.

Touch Secondary source of information
Crucial to people with disabilities Touch is not localised 3 Types of sensory receptor Thermoreceptors - heat and cold Nociceptors - intense pressure, heat and pain Mechanoreceptors - pressure rapidly adapting slowly adapting two-point threshold test Kinesthesis awareness of position of body and limbs three types rapidly adapting (moving of limb) slowly adapting (movement and static position) positional receptors (static position only)

Engineering Models of Human Performance
Predictive Quantitative time to perform time to learn number and type of errors time to recover from errors Learnable and usable by systems designers Usefully approximate

LTM Processes Remembering or Storing Forgetting (2 Theories) Retrieval
Repeat rehearsal or exposure to information aids remembering Ebbinghaus’s Total time hypothesis Baddeley’s Distribution of practice effect. Factors boosting memorability: familiarity, concrete images, meaningfulness, structure. Forgetting (2 Theories) Decay Ebbinghaus - information decays logarithmically Jost’s Law - Older memories more durable Interference Losses Retroactive interference (newer knowledge inhibits older) Proactive inhibition (older knowledge reappears) Non-emotive words more durable than emotive words (exhibited in nostalgia of ‘good old days’) Difficulty in proving forgetfulness. Associations need to be exercised. Retrieval Recall and Recognition Categorisation, vivid imagery and familiarity aid retrieval.

Reasoning Deductive Reasoning Inductive Reasoning Abductive Reasoning
Derives the logically necessary conclusion from the given premises. Some people are babies, some babies cry. Some people cry? Truth and validity clash. Bring world knowledge into reasoning process to facilitate shortcuts. Inductive Reasoning Generalising from cases we have seen to infer information about cases we have not seen Every elephant we have seen has a trunk; therefore we infer all elephants have trunks Unreliable inference Cannot be proved; only disproved by producing a ‘trunkless’ elephant. Wason’s Cards. Need to disprove statement not add more proof. Abductive Reasoning Reasoning from a fact to the action or state that caused it. Used to derive explanations from the events we observe. Often unreliable; though we hold such explanations until they can be disproven.

More Slides from… Washington State University School of EECS
CptS Human Computer Interaction

Long Term Memory The Human World-Wide Web Two types Representations
episodic - events, organized temporally semantic - facts, organized associatively Representations semantic nets frames scripts

Semantic Network university is a is a UI is a UW WSU vandal husky
cougar animal is a is a

Frames Extends semantic nets to include structured hierarchical information University Fixed: type of school Default: has colleges Variable: public/private WSU Fixed: type of University Default: public Variable: campus

Scripts Stereotypical information
Entry conditions: need job, have money Result: educated, less money Props: books, schedule, new car Roles: instructor talks, students listen Scenes: classroom, dorm Tracks: internships, apprenticeships

Processes How does information get from short term memory into long term memory? Total time hypothesis - hit the books Distribution of practice effect - don’t cram Meaning - concrete better than abstract faith age cold tenet quiet logic idea value past boat tree cat child rug plate gun flame head Structure, familiarity and concreteness

How We Forget Decay Interference Logarithmically - forget most early
Jost’s Law - if two equally strong memories at a given time, then the older is more durable. Interference retroactive interference - old phone number proactive inhibition - driving to the old house emotion - good old days, forget the mundane

Information Retrieval
How do we recall details? Categorization Visualization 1 bun 2 shoe 3 tree 4 door 5 hive 6 sticks 7 heaven 8 gate 9 wine 10 hen

Real Intelligence How is information processed and manipulated?
Animals - receive and store info, but do not process it as well as humans Computers - receive and store info better then humans, but do not process it as well as humans

Human Intelligence Humans use information to Human thought is
Reason & solve problems Even if the info is partially missing or completely absent! Human thought is conscious & self-aware capable of imagination

Reasoning Inferring missing information Deductive - conclusions
Inductive - generalizations Abductive - suppositions

Deductive Reasoning If A then B The phone rings when I’m in the shower
A. Therefore B not B, therefore not A. The phone rings when I’m in the shower If I’m in the shower, then the phone rings When the phone rings, take a shower No shower? Phone doesn’t ring.

Inductive Reasoning Specific A has property B then all A is B
Elephants have trunks Computers are slow Classes are exciting Students hand homework in on time WHETS is fun Geeks are rich

Wason Cards If a card has a vowel on one side it has an even number on the other. True or False? 4 E 7 K

Abductive Reasoning From fact to the action that caused it
Totalled car Black eye 4.0 GPA Smile/frown Core dump Phone ring

Problem Solving Using knowledge to find a solution Gestalt theory
Problem space theory Analogy

Gestalt Theory Finding new solutions Reproductive problem solving
Learned behavior, trial and error Behavioralist Fixation Productive problem solving Invention, innovation, insight Pendulum problem

Problem Space Theory Mapping out a solution step by step
Problem states, goal state, current state Legal state transition operators Heuristics, e.g. means-ends analysis Examples Games: 15 puzzle, chess Tasks: Setting the VCR clock Life (emphasis on “legal”)

Analogy Applying one solution to a different problem
Analogical mapping Purely productive reasoning is hard (10%) Drawing analogies is easier (80%) Existing solution “semantically close” to problem domain

Skill Acquisition Solving problems that are not completely new
e.g. Chess Same goal (different goal states) Same transitions Different “skills” Problem groups novices group problems superficially experts group problems conceptually

ACT Skill Acquisition Model
How is skill acquired? General rules Proceduralization Specific rules Generalization Tuned rules

Errors How do we make mistakes? Slips - change in context of skill
Mental models - incorrect interpretation of the evidence

Design How do we use what we know about humans to make better user interfaces? Guidelines Models Evaluation

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