chapter 1 introduction to cognitive psychology. the complexity of cognition cognition involves...

Chapter 1Introduction 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

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


•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

Simple RT Choice RT


•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


•Donders (1868)

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


•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

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.


•Ebbinghaus (1885)

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


•Ebbinghaus (1885)

– After some time, he relearned the list

•Short intervals = fewer repetitions to relearn

– Learned many different lists at many different retention intervals


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

/(initial repetitions)

– S = (Ri-Rr)/Ri

– Forgetting curve shows savings as a function of retention interval

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


•Wundt (1897)

– First psychology laboratory

– University of Leipzig, Germany

– RT experiments


•Wundt (1897)

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

visual auditory

gustatory

olfactory

haptic


•Wundt (1897)

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


•John Watson noted two problems with this:

– Extremely variable results from person to person

– Results difficult to verify

•Invisible inner mental processes

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


•Watson (1920) – “Little Albert” experiment

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


•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…

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

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

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?

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

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

Stimulus intensity represented by firing rate, not spike magnitude

axonSIGNAL PROPAGATION without decrease in size

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

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

1 2 3 4 5 6 7

A

B

C

INHIBITORYNEURALCIRCUIT

Firi

ng

rate

(B

)

4 3-5 2-6 1-7

Receptors

time timetimetime

Optic nerve brain areas: neurons ever more specialized

Hubel & Wiesel (1965): feature detectors

simple cells complex cells End-stopped cells

convergence

+ excitation

+ inhibition

…but how to recognize a specific face?

NEURAL CODES

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

FRONTAL

OCCIPITAL

PARIETAL

TEMPORAL

BRAIN LOBES: outer covering = cerebral cortex

Motor functionLanguageThoughtMemory

VisionAttentionTouch

Vision

LanguageMemoryHearingForm perception

THALAMUSVisionHearingTouch

CEREBELLUMSensory integrationMotor control

AMYGDALAEmotionsEmotional memory

HIPPOCAMPUSMemory

SUBCORTICAL AREAS (INSIDE THE BRAIN)

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

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 _ =

fMRI: functional magnetic resonance imaging

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

Active area less oxygen, more iron

BRAIN IS ADAPTIVE, FLEXIBLE

EXPERIENCE-DEPENDENT PLASTICITY

firi

ng

rate

beforetraining

aftertraining

“greebles”

teachingneurons new tricks

“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]

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

INTERACTIVE ACTIVATION MODEL (McClelland & Rumelhart, 1981)

strongest activation wins

Word FORK ROOF

Letter F K O R

Feature

Stimulus K

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

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

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

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)

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”

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

TOP-DOWN influence HELPS to reduce errors:

Control condition (objects not labeled):illusory conjunctions occur

Experimental condition:

CARROTLAKE

TIRE

Illusory conjunctions LESS LIKELY

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

We have a theory for that, too!

RECOGNITION-BY-COMPONENTS THEORY (Biedermann, 1987)

GEONS ARE (MOSTLY) VIEW INVARIANT: ?

But…

3 parallel edges seen from many angles

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

Perceptual organization Gestalt psychology

Structuralism: image consists of dots (sensations)

Sensations combined to result in perception of the glasses

Overall PATTERN matters. But how do you combine sensations?

XX

ONESTIMULUS

THREEPERCEPTIONS

BOTTOM-UP

ONESTIMULUS

ONEPERCEPTION

TOP-DOWN

GESTALT LAWS OF PERCEPTUAL ORGANIZATION

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


LAW OF SIMILARITY:similar things grouped together


LAW OF GOOD CONTINUATION:smoothest path determines sameness


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


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


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

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]

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

http://www.youtube.com/watch?v=FLi_IQgCxbo&feature=related

DISTINGUISH OBJECT-BACKGROUND

SEGMENTATION IN SPEECH PERCEPTION

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

-voice identification devices

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

“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

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?

chapter 1 introduction to cognitive psychology. the complexity of cognition cognition involves...

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