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:Color WavelengthRed 629Red-Orange 596Yellow-Orange 582Green-Yellow 571Yellow-Green 538Green 510Blue-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)

Macular degeneration

Diabetic retinopathy

Cataracts

Tunnel vision

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.asphttp://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

Work Station Ergonomics – to Facilitate I/O

Large Range of Physical ImpairmentsComplete 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 strengthTremor/lack of accuracySlowness

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

SHORT-TERM (WORKING) MEMORY

AUDITORY IMAGESTORE

VISUAL IMAGESTORE

R = SemanticD = InfiniteS = Infinite

R = AcousticD = 1.5 [0.9-3.5] sS = 5 [4.4-6.2] letters

R = VisualD = 200 [70-1000] msS = 17 [7-17] letters

R= Acoustic or VisualD (one chunk) = 73 [73-226] sD (3 chunks) = 7 [5-34] sS = 7 [5-9] chunks

R = RepresentationD = Decay TimeS = SizeC = Cycle Time

PERCEPTUALPROCESSOR

C = 100 [5-200] ms

COGNITIVEPROCESSOR

C = 70 [27-170] ms

MOTORPROCESSOR

C = 70 [30-100] MS

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

People

Good1. xxx

2. yyy

3. zzz

Bad1. 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

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

Distributed Cognition

Cognitive System – the people, artifacts and environments

Communicative pathways – the information channels

Describes information flow in terms of propagation across representational state Information is transformed through different

media (computers, displays, paper, heads)

What’s involved

The distributed problem-solving that takes place

The role of verbal and non-verbal behavior The various coordinating mechanisms that

are used (e.g., rules, procedures) The communication that takes place as the

collaborative activity progresses How knowledge is shared and accessed

Activity Theory

Long history from cognitive science HCI proponent: Bonnie Nardi

Explains human behavior in terms of our practical activity with the world

Provides a framework that focuses analysis around the concept of an ‘activity’ and helps to identify tensions between the different elements of the system

Two key models: one outlines what constitutes an ‘activity’; one models the mediating role of artifacts

Activity Theory

Unit of analysis is an activity Components:

subject, object, actions, operations

Noun Held by subject,motivates activity“object of game”

Goal-directedprocesses“tasks”

How actionis carried out

Individual model

A.T. Principles

Key idea: Notion of mediation by artifacts Our work is a computer-mediated activity

Starring role goes to activity In “regular” HCI, stars are person and machine

Context is not “out there”. It is generated by people in activities

Example: call center

DCog: Examine how information is transformed as it

goes from caller, to employee, into the system for information, back to employee and then caller…

Activity Theory Examine tensions between parts of the system

such as community, tools, rules, etc.

Situated Action

Noted proponent: Lucy Suchman

Much of the theory that underlies ethnography

Structuring of an activity grows out of immediacy of the situation

People engage in opportunistic, flexible ways to solve problems

Situated Action

Studies situated activity or practice Activity grows out of the particulars of a

situation Improvisation is important

Basic unit of analysis is “the activity of persons acting in a setting”

Example

Need 3/4 of 2/3 of cup of cottage cheese Just has a simple measuring cup available

Person solves problem by Measuring 2/3 cup Pouring out into a circle Divide into quadrants Take away one

One time solution to one time problem

Other comments on S.A.

Emergent property of moment-by-moment interactions

Improvisation Detailed temporal accounts De-emphasizes rigid plans and rational

problem solving

Comparing Models

The role of goals or intentions S.A.: “retrospective reconstructions” A.T. & D.C: central

Persistent structures S.A.: emphasize emergent/ contingent/ improvisatory

over routine/predictable A.T.: our activity assimilates experience of humanity D.C.: much focus on transformation of artifacts over

time

Comparing Models

People and things MHP: model each as a “machine”, study the

diad of H-C S.A.: qualitatively different, but mostly reactive A.T.: individual at center D.C.: both are agents, study multi-agent

system

Some Commentary

Take the reading with a grain of salt.

How does this influence design?