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Human CognitionHuman Cognition

Fang ChenChalmers University of Technology

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Human cogitionHuman cogition• Perception and recognition• Memory• Attention, emotion• Learning• Reading, speaking, and listening• Problem solving, planning, reasoning, decision

making• Individual difference

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Human cognitionHuman cognition

• Why?– Understand human cognitive capacity and limitation– One importent part in HCI

• How?– own experience?– the common sense?– Individual difference

Optical IllusionsOptical Illusions

the Ponzo illusion the Muller Lyer illusion

Optical IllusionsOptical Illusions Optical IllusionsOptical Illusions

2

Information processingInformation processing

Long-TermMemory

ResponseExecution

Response Activation

Feedback

Attention and emotion

Out

put

Environment

SensoryStore:

visual auditoryhaptic

movement

PerceptionWorking memory

RecognitionReasoningProblem solvingDecision making

The sensors on human bodyThe sensors on human body-- Sensory modalitiesSensory modalities

On the head•Vision•Hearing•Balance•Taste•Smell

On the skin:•Head-cold•Pain•Touch-Pressure

On muscles:• Muscle and tendon receptors

On joints:•Changes in joint position•Speed of movement•Position of the joint•Pain sensation

The human brainThe human brain

cortexcortexsomatic sensory somatic sensory cortexcortex

Optical IllusionsOptical Illusions 3/53/5

Human Visual SystemHuman Visual System

• Light passes through lens• Focussed on retina

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Interpreting the visual signal Interpreting the visual signal

• Visual processing involves the transformation and interpretation of a complete image

• Expectations affects the way an image is perceived• The visual system compensates for:

– Movement and changes in luminance.

• Context is used to resolve ambiguity

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ReadingReading

• Several stages:– visual pattern perceived– decoded using internal representation of language– interpreted using knowledge of syntax, semantics, pragmatics

• Reading involves saccades and fixations• Perception occurs during fixations• Word shape and color is important to recognition• Negative contrast improves reading from computer screen

The earThe ear

Physical apparatus:outer ear – protects inner and amplifies soundmiddle ear – transmits sound waves as vibrations to inner earinner ear – chemical transmitters are released

and cause impulses in auditory nerve

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HearingHearing

• Provides information about environment:distances, directions, objects etc.

• Sound– pitch – sound frequency– loudness – amplitude– timbre – type or quality

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Writting and speakingWritting and speaking

• Written language is grammatical• Speaking has redundant information

The cognitive differences between speech perception and reading text

Can take input from any directionBe accessible only in the focus visual area

Contain numerous hints, such as pitch, intonation, stress, timing, to sentence structure and meaning.

There is no so many redundant information behind the word itself

Higher memory demand, the information is transient, a word is heard and then it ends.

The text can be continuously available

More ambiguous and unclear signalLess ambiguous

Spoken word is spread out in timeEach word can be seen as a whole

Listening to speechReading the test

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Interaural time difference, ITD

Interaural intensity difference, IID

3D 3D -- audioaudio

4

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?”Cone of confusion”Sound source

ConfusionConfusion

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TouchTouch

• Provides important feedback about environment.

• May be key sense for someone who is visually impaired.

• Stimulus received via receptors in the skin:– thermoreceptors – heat and cold– nociceptors – pain– mechanoreceptors – pressure

(some instant, some continuous)

• Some areas more sensitive than others e.g. fingers.

• Kinethesis - awareness of body position – affects comfort and performance.

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MovementMovement

• Time taken to respond to stimulus:reaction time + movement time

• Movement time dependent on age, fitness etc.• Reaction time - dependent on stimulus type:

– visual ~ 200ms– auditory ~ 150 ms– pain ~ 700ms

• Fits law:– The time taken to hit a target is a function of the size of the target

and the distance that has to be moved

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MemoryMemory

There are three types of memory function:

Sensory memories

Working memory (or short-term memory)

Long-term memory

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MemoryMemory

• Sensory memory– Buffers from stimuli received through senses

• Working memory (short term)– small capacity– rapid access (~ 70ms) & decay (~200 ms)

• pass to LTM after a few seconds

• Long-term memory– huge (if not “unlimited”)– slower access time (~100 ms) w/ little decay

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3126209401198971384

45, 12, 60, 25, 91, 42, 06,14, 19, 85, 97, 13, 84

cat, house, paper, laugh, people, red, yes, number, shadow, broom, rain, plant, lamp, chocolate, radio, one, coin, jet

5

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3126209401198971384

45, 12, 60, 25, 91, 42, 06,14, 19, 85, 97, 13, 84

cat, house, paper, laugh, people, red, yes, number, shadow, broom, rain, plant, lamp, chocolate, radio, one, coin, jet

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The magical number The magical number 7 7 ±± 2 2

• Geoger Miller 1956.• Peopel’s immediate memory capacity is very limited• Only remember 7 ± 2 chunks (number or words)

Stage TheoryStage Theory

Working Memory

Sensory Image Store

Long Term Memory

decay decay,displacement

chunking / elaboration

decay?interference?

maintenancerehearsal

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LongLong--term memory (LTM)term memory (LTM)

• Repository for all our knowledge– slow access ~ 1/10 second– slow decay, if any– huge or unlimited capacity

• Two types– episodic – serial memory of events– semantic – structured memory of facts,concepts, skills

semantic LTM derived from episodic LTM

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Semantic memory structureSemantic memory structure

• provides access to information• represents relationships between bits of information• supports inference

How do you know that animal is a dog, not a cat?

6

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LTM LTM -- Storage of informationStorage of information

• rehearsal– information moves from STM to LTM

• total time hypothesis– amount retained proportional to rehearsal time

• distribution of practice effect– optimized by spreading learning over time

• structure, meaning and familiarity– information easier to remember

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LTM LTM -- retrievalretrieval

recall – information reproduced from memory can be assisted by cues, e.g.

categories, imagery

recognition– information gives knowledge that it has been seen before– less complex than recall - information is cue

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LTM LTM -- ForgettingForgetting

decay– information is lost gradually but very slowly

interference– new information replaces old: retroactive interference– old may interfere with new: proactive inhibition

so may not forget at all memory is selective …

… affected by emotion – can subconsciously `choose' to forget

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ThinkingThinking

• Reasoning: inferring new information from what is already known

• Problem solving: the process of finding a solution to an unfamiliar task, using the knowledge we have

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ReasoningReasoning

• Deduction: derive logically necessary conclusion from given premises

• Induction: generalize from cases seen to cases unseen• Abduction: reasoning from event to cause

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Wason'sWason's cardscards

Is this true?

How many cards do you need to turn over to find out?

…. and which cards?

If a card has a vowel on one side it has an even number on the other

7 E 4 K

7

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Problem solving theoriesProblem solving theories

• Gestalt• Problem space theory• Analogy• Skill acquisition

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Mental modelsMental models• inferences about how to carry out tasks.• fathom what to do, when

– something unexpected happens – encountering unfamiliar systems.

• Engineers mental model ≠ users mental model.

Cognitive models describe and predict users’ problems solvingbehaviour with interactive systems. Cognitive models are used todesign and improve interactive systems.

---------------More in Chapter 12

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ErrorsErrors

Types of error

• slips– right intention, but failed to do it right– causes: poor physical skill,inattention etc.– change to aspect of skilled behaviour can cause slip

• mistakes– wrong intention– cause: incorrect understanding

humans create mental models to explain behaviour.if wrong (different from actual system) errors can occur

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EmotionEmotion

• Various theories• cognitive and physical responses to stimuli• The biological response - affect• Affect influences information process• Affect computing

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How emotions are manifested/measured How emotions are manifested/measured

• Physiological response– Heart rate– Respiration– Skin response– Blood pressure

• Questionnaire• Facial expression• Voice• Brain activity• Gestures and actions

Scott Brave and Cliff Nass: Emotion in Human-Computer Interactionhttp://www.research.umbc.edu/~asears/HCIHandbook/nass.html

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Attention in perception and display space (1)Attention in perception and display space (1)

• Selective attention– Visual sampling

• Pursuit – eye follows a target moving at a constant speed across the visual field

• Saccadic – jumped view• Location• Supervisory• Target search

– Optimality of selective attention• Select the relevant stimuli to attend at the appropriate times

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Attention in perception and display space (2)Attention in perception and display space (2)

• Paralle processing and divided attention– Several items within the view field might be processed

together

• Focus attention

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Goal and information presentationGoal and information presentation

• If we know exactly what we want to find out, we try to match this with the information that is available

• The way information is displayed can also greatly influence how easy or difficult it is to attend to appropriate piece of information

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Individual differencesIndividual differences

• long term– sex, physical and intellectual abilities

• short term– effect of stress or fatigue

• changing– age

• attentionAsk yourself:

will design decision exclude section of user population?