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Page 1: Chapter 1 Introduction to Cognitive Psychology

Chapter 1Introduction to Cognitive Psychology

Page 2: Chapter 1 Introduction to Cognitive Psychology

The Complexity of Cognition

•Cognition involves– Perception– Attention– Memory– Problem solving– Reasoning– Decision making

– All include “hidden” processes of which we may not be aware

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The First Cognitive Psychologists

•Donders (1868)– Mental chronometry

•Measuring how long a cognitive process takes

– Reaction-time (RT) Experiment

•Measures interval between stimulus presentation and person’s response to stimulus

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The First Cognitive Psychologists

•Donders (1868)

– Simple RT task: participant pushes a button quickly after a light appears

– Choice RT task: participant pushes one button if light is on right side, another if light is on left side

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Simple RT Choice RT

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The First Cognitive Psychologists

•Donders (1868)

– Choice RT – Simple RT = Time to make a decision

•Choice RT = 2.1 sec

•Simple RT = 2 sec

•1/10th sec to make decision

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The First Cognitive Psychologists

•Donders (1868)

– Mental responses cannot be measured directly but can be inferred from the participant’s behavior.

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The First Cognitive Psychologists

•Helmholtz (~1860s)

– Unconscious inference

•Some of our perceptions are the result of unconscious assumptions we make about the environment

– We infer much of what we know about the world

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Caption: The display in (a) looks like (b) a gray rectangle in front of a light rectangle; but it could be (c) a gray rectangle and a six-sided figure that are lined up appropriately or (d) a gray rectangle and a strange-looking figure that are lined up appropriately.

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The First Cognitive Psychologists

•Ebbinghaus (1885)

– Read list of nonsense syllables aloud many times to determine number of repetitions necessary to repeat list without errors

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The First Cognitive Psychologists

•Ebbinghaus (1885)

– After some time, he relearned the list

•Short intervals = fewer repetitions to relearn

– Learned many different lists at many different retention intervals

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The First Cognitive Psychologists

•Ebbinghaus (1885)– Savings = [(initial repetitions) – (relearning repetitions)]

/(initial repetitions)

– S = (Ri-Rr)/Ri

– Forgetting curve shows savings as a function of retention interval

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Ebbinghaus’s retention curve, determined by the method of savings. (Based on data from Ebbinghaus, 1885.)

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The First Cognitive Psychologists

•Wundt (1897)

– First psychology laboratory

– University of Leipzig, Germany

– RT experiments

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The First Cognitive Psychologists

•Wundt (1897)

– Structuralism: experience is determined by combining elements of experience called sensations

visual auditory

gustatory

olfactory

haptic

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The First Cognitive Psychologists

•Wundt (1897)

– Analytic introspection: participants trained to describe experiences and thought processes in response to stimuli

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The First Cognitive Psychologists

•John Watson noted two problems with this:

– Extremely variable results from person to person

– Results difficult to verify

•Invisible inner mental processes

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The Rise of Behaviorism

•John Watson proposed a new approach called behaviorism

– Eliminate the mind as a topic of study

– Instead, study directly observable behavior

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The Rise of Behaviorism

•Watson (1920) – “Little Albert” experiment

– 9 month old became frightened by a rat by pairing a loud noise with every presentation of the rat

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The Rise of Behaviorism

•Watson (1920) – “Little Albert” experiment

– Behavior can be analyzed without any reference to the mind

– Examined how pairing one stimulus with another affected behavior

In summary: cognitivism was in crisis…

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9am

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Skinner:

S R

Operant conditioning: reinforcers [e.g. food]

“Verbal behavior” (1957): language learned via imitation and reward.

Chomsky: kids use untrained sentences; make errors given reward.

COGNITIVE REVOLUTION

MIND = COMPUTER-information-processing device-several stages

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computer I OInput processor

Memory

unit

Arithmetic unit

human I Filter Detector To memory

Cherry (1953) experiment

Attend Left

attended sentences remembered

physiological R

mental R

behavioral R

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RT

Angle difference

Mental rotation: Shepard & Metzler (1971)

Davachi et al (2003): Measure brain activity during learning

read 200 words: create an image“dirty” = “garbage dump”

20 hrs later: same 200 words“did you see this word?” Y/NResult: 54% from the 1st group remembered

Bra

in a

ctiv

ity

remembered forgottenRESULT OF MEMORY TEST

Same or different?

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10am

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sound to electricity

Auditoryarea

Motorarea

to arm and hand

+ Knowledge:1. Alarm will go off

again in 10 min2. Still time to get to

class

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Neurons: building blocks of nervous system

Golgi first to prove how a neuron looks like

S

receptordendrites

axon

TRANSDUCTION: energy to energy conversion (just like ATM)

Why study single neurons?

axon

minielectrode

oscilloscope1/1000 sec

volt

ag

e

1/10 sec

spikes = action potentials

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Stimulus intensity represented by firing rate, not spike magnitude

axonSIGNAL PROPAGATION without decrease in size

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HOW NEURONS COMMUNICATE?

Direct contact? (touch?) NO!

SYNAPSE (space between axon and next neuron)

Early 1900s: action potentials DO NOT travel across synapses -they TRIGGER a chemical process -synaptic VESICLES open and release chemicals

(NEUROTRANSMITTERS)

I

E

electrodes

increased firing

decreased firing

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1 2 3 4 5 6 7

A

B

C

EXCITATORYNEURALCIRCUIT

Firi

ng

rate

(B

)

4 3-5 2-6 1-7

Receptors

Properties:CONVERGENCEINTERACTION OF E & I

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1 2 3 4 5 6 7

A

B

C

INHIBITORYNEURALCIRCUIT

Firi

ng

rate

(B

)

4 3-5 2-6 1-7

Receptors

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time timetimetime

Optic nerve brain areas: neurons ever more specialized

Hubel & Wiesel (1965): feature detectors

simple cells complex cells End-stopped cells

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convergence

+ excitation

+ inhibition

…but how to recognize a specific face?

NEURAL CODES

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SPECIFICITY CODING: representation of a specific stimulus

GRANDMOTHER CELL: responds to only one stimulus

firi

ng r

ate

neurons

firi

ng r

ate

neurons

DISTRIBUTED CODING: the pattern matters, not cells

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FRONTAL

OCCIPITAL

PARIETAL

TEMPORAL

BRAIN LOBES: outer covering = cerebral cortex

Motor functionLanguageThoughtMemory

VisionAttentionTouch

Vision

LanguageMemoryHearingForm perception

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THALAMUSVisionHearingTouch

CEREBELLUMSensory integrationMotor control

AMYGDALAEmotionsEmotional memory

HIPPOCAMPUSMemory

SUBCORTICAL AREAS (INSIDE THE BRAIN)

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NEUROPSYCHOLOGY: behavior after brain damage

Behavioral breakdowns specific to brain damage.

SINGLE DISSOCIATION: STM intact, LTM lost

DOUBLE DISSOCIATION:

Person 1: STM intact, LTM lostPerson 2: STM lost, LTM intact

Proof that1) STM & LTM have different mechanisms2) STM & LTM independent of one another

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COGNITION: how to measure it in the brain?

BRAIN IMAGING

PET (positron emission tomography):-blood flow indicates cognitive process-radioactive stuff injected into blood-machine measures radioactivity levels

SUBTRACTION TECHNIQUE:

control differencestimulation _ =

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fMRI: functional magnetic resonance imaging

-no radioactive material involved-hemoglobin carries oxygen-contains iron molecules-have magnetic properties

Active area less oxygen, more iron

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BRAIN IS ADAPTIVE, FLEXIBLE

EXPERIENCE-DEPENDENT PLASTICITY

firi

ng

rate

beforetraining

aftertraining

“greebles”

teachingneurons new tricks

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“perception is simple and easy”

1960s: “will build robot within 10 years that can see, feel and act like human”

Stimulus energy & [knowledge, context, experience]

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Related 83% correct

Misleading 40% correct

Unrelated 50% correctPalmer (1975):Context influences perception

Follow the lead of early cognitive psychologists…TASK: perceive lettersTHEORY: TEMPLATE MATCHING (perception based on features)

K K K K

need template for every orientation

How would a machine do it?

briefly flash stimulus

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INTERACTIVE ACTIVATION MODEL (McClelland & Rumelhart, 1981)

strongest activation wins

Word FORK ROOF

Letter F K O R

Feature

Stimulus K

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WORD RECOGNITION

Word FORK ROOF

Letter-position F F F F K K K K O O O O R R R R

Feature

Stimulus FORK

strongest activation wins

F,R,K K R, K O O, R F

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WORD SUPERIORITY EFFECT (Reicher, 1969)

stimulus mask present Which appeared?flashed

Ka) FORK XXXX XXXX QUICK & ACCURATE

M

Kb) K XXXX XXXX SLOW & INACCURATE

M

Kc) RFOK XXXX XXXX SLOW & INACCURATE

M

-LETTERS IN WORDS AFFECTED BY CONTEXT

-LETTERS IN WORDS NOT PROCESSED LETTER BY LETTER

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FEEDBACK ACTIVATION explains this result:

FORK ROOF

F1 K4 O2 R3

-no feedback when standalone letter presented-word level sends FB to letter level as reinforcement

TOP-DOWNFB

WORDS

LETTERS

FEATURES

BOTTOM-UPPROCESSING

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FEATURE INTEGRATION THEORY (TREISMAN, 1986)

object preattentivestage

focusedattention

stageperception

-analyze into features

-not conscious

combinefeatures

Do we really break objects into features? Do features exist independently of objects?

1 8Treisman & Schmidt (1982)

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1 8Task: ID the numbers, then the rest

Interesting errors… RED CIRCLE, GREEN TRIANGLE, etc.

ILLUSORY CONJUNCTIONS (18% of responses)

“redness”“curvature”“tilted line”…

not yet associated with a specific object

Attention part of conscious perception: no errors if asked to focus on figures

“VISUAL ALPHABET”

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Skeptic: “Hey, but I still don’t buy it! I SEE objects, not features!”

Answer: BALINT’S SYNDROME (case of R.M.)

parietal lobe damagecan’t focus attention on individual objects

TASK: identify colored letters

T O23% of RESPONSES = illusory conjunctions (“red T”, “blue O”)

Watched it for

10 seconds!

CONCLUSION: you need attention, otherwise ONLY features perceived

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TOP-DOWN influence HELPS to reduce errors:

Control condition (objects not labeled):illusory conjunctions occur

Experimental condition:

CARROTLAKE

TIRE

Illusory conjunctions LESS LIKELY

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Features = lines, curves, colorsWhat about 3D object perception?

We have a theory for that, too!

RECOGNITION-BY-COMPONENTS THEORY (Biedermann, 1987)

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GEONS ARE (MOSTLY) VIEW INVARIANT: ?

But…

3 parallel edges seen from many angles

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Strength of Biederman’s theory:

9 geons 3 geons

GEONS ARE (MOSTLY) DISCRIMINABLE: each geon can be distinguished from the others

GEONS ARE (MOSTLY) RESISTANT TO VISUAL NOISE: low light, fog, occlusion

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Perceptual organization Gestalt psychology

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Structuralism: image consists of dots (sensations)

Sensations combined to result in perception of the glasses

Overall PATTERN matters. But how do you combine sensations?

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XX

ONESTIMULUS

THREEPERCEPTIONS

BOTTOM-UP

ONESTIMULUS

ONEPERCEPTION

TOP-DOWN

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF PREGNANZ (LAW OF SIMPLICITY):simplest configuration perceived

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF SIMILARITY:similar things grouped together

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF GOOD CONTINUATION:smoothest path determines sameness

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF PROXIMITY (NEARNESS):closely spaced things grouped together

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF COMMON FATE:same direction of movement groups things together

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GESTALT LAWS OF PERCEPTUAL ORGANIZATION

LAW OF FAMILIARITY: if the collection of parts is meaningful, it forms a group

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GESTALT LAWS describe our everyday world

…really, they’re HEURISTICS (rules of thumb):work most of the time, not always

contrast with ALGORITHMS: always correct

Slow, analytic process

Fast, perceptual process

Perception is INTELLIGENT, although naively considered easy and trivial

[we see patterns, where there were none][irreversible]

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1960s: perception is simple; will build robot that sees within 10 years1997: computer beats human in chess2005: computer-driven cars navigate 130+ miles of desert road

Navigation

Cognition & computation

Object recognition ???

RETINAL IMAGE IS AMBIGUOUS

-inverse projection problem

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DISTINGUISH OBJECT-BACKGROUND

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SEGMENTATION IN SPEECH PERCEPTION

BLURRY IMAGE: what is the threshold for perception? How do we do it?

-voice identification devices

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Change in LIGHTNESS due to object properties or illumination:Computer can’t tell whether (a) and (b) are part of the same object

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“I scream, you scream, we all scream for ice cream.”

Same sound, different context for meaning

TRANSITIONAL PROBABILITIES: whether two neighboring syllables are part of the same or different word

Saffran et al (1996): infants sensitive to things that occur together regularly in the environment

Stimulus: …bidakupadotigolabutupiro… …golabutupirobidakupadoti… …

Within-word transition probability =100% (da-ku)Between-word transition probability = 33% (ku-pa)

When head turns to light sound starts

When head turns away sound stops

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Saffran et al (1996) results:

LEARNING STAGE

TEST STAGE

2 minutes listening

“tibida” (part)“padoti” (word)

Wholeword

Partword

List

enin

g t

ime (

sec)

-never heard these words before-no pauses between words-only 2 minutes to learn

Inborn capacity or learned? This is the knowledge that computers need?