Chapter 1 Introduction to Cognitive Psychology
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Transcript of Chapter 1 Introduction to Cognitive Psychology
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
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
Simple RT Choice RT
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
The First Cognitive Psychologists
•Donders (1868)
– Mental responses cannot be measured directly but can be inferred from the participant’s behavior.
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
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.
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
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
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
Ebbinghaus’s retention curve, determined by the method of savings. (Based on data from Ebbinghaus, 1885.)
The First Cognitive Psychologists
•Wundt (1897)
– First psychology laboratory
– University of Leipzig, Germany
– RT experiments
The First Cognitive Psychologists
•Wundt (1897)
– Structuralism: experience is determined by combining elements of experience called sensations
visual auditory
gustatory
olfactory
haptic
The First Cognitive Psychologists
•Wundt (1897)
– Analytic introspection: participants trained to describe experiences and thought processes in response to stimuli
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
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
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
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…
9am
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?
10am
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
11am
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
1pm
“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
2pm
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
3pm
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
GESTALT LAWS OF PERCEPTUAL ORGANIZATION
LAW OF SIMILARITY:similar things grouped together
GESTALT LAWS OF PERCEPTUAL ORGANIZATION
LAW OF GOOD CONTINUATION:smoothest path determines sameness
GESTALT LAWS OF PERCEPTUAL ORGANIZATION
LAW OF PROXIMITY (NEARNESS):closely spaced things grouped together
GESTALT LAWS OF PERCEPTUAL ORGANIZATION
LAW OF COMMON FATE:same direction of movement groups things together
GESTALT LAWS OF PERCEPTUAL ORGANIZATION
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]
4pm
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
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?