Human AbilitiesSensory, motor, and cognitive capabilities

Outline

Human capabilities Senses Motor systems Information processing

Memory Cognitive Processes

Selective attention, learning, problem solving, language

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 understanding of human capabilities does change, ie Cognitive neuroscience Theories of color perception Effect of groups and situation on how we act

and react

Human Capabilities

Why do we care? Better design! Want to improve user performance

Knowing the user informs the design Senses Information processing systems Physical responding

Senses (Our Input System)

Sight, hearing, touch important for current HCISmell, taste ???

Abilities and limitations affect design

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)

ColorDistinguishable hues, optical illusionsAbout 9 % of males are red-green

colorblind! Acuity

Determines smallest size we can seeLess 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

Color Surround

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

Effect of Colored Text on Colored Background

Black text on red

Gray text on red

Yellow text on red

Light yellow text on red

Green text on red

Light green text on red

Blue text on red

Pale blue text on red

Dark red text on red

Red text on red

Rose text on red

Effect of Colored Text on Colored Background

Black text on dark blue

Gray text on dark blue

Yellow text on dark blue

Light yellow text on dark blue

Green text on dark blue

Light green text on dark blue

Blue text on dark blue

Pale blue text on dark blue

Dark red text on dark blue

Red text on dark blue

Rose text on dark blue

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)

Sensitivity, Dexterity, Flexibility, Speed

Where important? Mouse, Other I/O, VR, surgery

Smell

Joseph Kaye, “Making scents: aromatic output for HCI” ACM Interactions Volume 10, Number 1 (2004), Pages 48-61

Solenoid-controlled scent bottles

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) memoryConscious thought, calculations

Long-term memoryPermanent, 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

Perceptual or Sensory Memory

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 (7 - 17 letters visual;

4 - 6 auditory)

Sensory Stores

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 Processors – interpret signal into semantically

meaningful Pattern recognition, language, etc.

Short Term Memory

Use “chunks”: 7 +- 2 units of information

Symbolic, nonphysical acoustic or visual coding

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

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

File system full

LT Memory Structure

Episodic memoryEvents & experiences in serial form

• Helps us recall what occurred

Semantic memoryStructured 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 AttentionLearningProblem SolvingLanguage

Selective Attention

We can focus on one particular thingCocktail party chit-chat

Salient visual cues can facilitate selective attentionExamples?

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 applyOr 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 onesReasons from a fact to theaction or state that caused it

Observations

We are more heuristic than algorithmicWe 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 shortcutsForcing plans will bore user

Have active rather than passive helpRecognize 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. Medium term c. Long term 2. Processes a. Selective attention b. Learning c. Problem solving d. Language

III. Motor system A. Hand movement B. Workstation Layout

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

Class Discussion:Model Human Processor

What are the three major subsystems and their functions? What does it mean to say that certain subprocessors have

“variable rates?” What are some of the other assumptions underlying the

MHP model? How good is the model?

Scenarios

Make sure it is a story withActors (at least one person)Actions (not just the context)

Good focus on the negativeTry to follow through with what the

person does