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8/14/2019 Learning Chapter 3
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Chapter 3
Pavlovian Conditioning
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Pavlovian Responses: Its not just aboutsalivation..
salivation, eye blinks, startle,nausea, tears-
but also.
pain attraction
anxiety arousal
fear happiness
disgust amusementsadness relaxed state
repulsion love (the kind you fall into)
anger
Classical conditioning applies to responses that we do not experience
as voluntary, purposeful, or under our willful control.
They involve passive responses---responses that happen to us, or that we undergo.
We salivate, but we dont do salivation like we do our chores.
A neurological view of Pavlovian responses has also been proposed---
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The Nervous System
Classical
Conditioning
Operant
Conditioning
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Autonomic Nervous System (ANS)
Sympathetic NSArouses
(fight-or-flight)
Parasympathetic NSCalms
(rest and digest)
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The basic form of classicalcond.
A new stimulus gets paired withanother stimulus that produces apredictable, automatic response (reflexor autonomic activity).
The new stimulus can then come toelicit the original automatic response.
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The basic form of classicalcond.
+
Loud thunder automatically causes startle/fear
After repeated pairing of lightning with thunder, lightning itself produces the response
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Fears/PhobiasBeing stuck with a needle causes pain/fear
Pain/Fear/Stress+
Fear/Stress
Now the sight of a syringe cause fear/stress
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Attraction
Arousal/Attraction+
Arousal/Attraction
Closeness/Caress produces attraction
Security blankets, fetishes, inappropriate attractions (pedophilia)
http://www.mysweetaromas.com/images/Ck%20Be%20Perfume%20by%20Calvin%20Klein%20for%20Women.jpghttp://www.mysweetaromas.com/images/Ck%20Be%20Perfume%20by%20Calvin%20Klein%20for%20Women.jpg8/14/2019 Learning Chapter 3
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Food/Taste Aversions
Nausea/Vomiting
Alcohol causes nausea, dizziness, vomiting
+
Sight, taste, smell
Sight, taste, smell
Revulsion/Disgust
Same with foods. The illness might
even be due to other conditions,
such as viruses, flu, etc
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Musical Responses
Fear
Fear
Theme from Jaws
Tubular Bells
+
+
HappyOur Song +
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Unpopular Mustache
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Ivan Pavlov (1849-1936)
Russian Physiologist
Specialty: Digestion
Nobel Prize, 1904, for his work
on the digestive system
b. Ryazan, Russia
Poor: Father a priest
Started as seminarian. Left to study physical sciences, U. St. Petersburg
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Pavlov in his lab with hisfavorite experimental subject
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Pavlovs accidental discovery
Wanted to measure quantity andcomposition of saliva in response tofood in mouth.
Problem: dogs began to salivate before
food was administered, to everyonesannoyance.
Salivated to sight of researchers, door opening,footsteps, bowl
Pavlov called this phenomenon PsychicSecretions
He realized he had discoveredsomething psychological, and, aftermuch debate, directed his research to
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Pavlovs Experiments
Before conditioning, food produces salivation.However, a tone (neutral stimulus) does not.
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Pavlovs Experiments
During conditioning, the neutral stimulus (tone)and the food are paired, resulting in salivation.After conditioning, the neutral stimulus (tone)
elicits salivation.
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Formal Definitions
An unconditioned stimulus (US) A stimulus that triggers an unconditioned
response.
Examples: food, loud noises, painful stimuli
An unconditioned response (UR) An unlearned response to an
unconditioned stimulus. Examples: salivation to food, jumping when
hearing a loud noise, moving away fromsomething painful
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Formal Definitions
A conditioned stimulus (CS) A neutral stimulus (an event) that comes
to evoke a classically conditioned
(learned) response due to beingpresented shortly before the US. In Pavlovs experiments, the CS was the tone.
A conditioned response (CR) A learned response to a classically
conditioned stimulus. In Pavlovs experiments, salivation to the bell was
the CR.
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Learning the 4 Key Terms
US
UR
CS
CR
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First, identify the existingreflex pairThis reflex pair is always the USUR
The rest is easy.
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Nice Notation.
US UR (identify the reflex pair)
CS : US UR (pair a neutral stim. with theUS)
CS CR (CS elicits response; nowcalled CR)
Food Salivation
Tone : Food Salivation Tone Salivation
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What use?
Based on our experiences, classicalcondition builds a set of signals orpredictive cues for potentially important
things to come. Builds an early warning system: even
warning us of good things to come.
We become physiologically prepared forwhat might be coming next.
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Factors that affectconditioning Pairing CS and US (4 ways)
Contiguity (closeness in time)
Contingency (predictive value of CS)
Stimulus Features
Overshadowing: Salience, intensity, Sensory preconditioning
Prior Experience Latent Inhibition
Blocking Number of Pairings
Intertrial Interval
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Contemporary human eyeblink preparation
Just relax
Puff Blink
Bell : Puff Blink
Bell Blink
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Pairing: Trace Conditioning
The CS begins and ends before the US is presented.
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Delayed Conditioning
The CS and US overlapi.e., the US is presented while the CS is still being presented
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Simultaneous Conditioning
The CS and US coincide exactly in time.
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Backward Conditioning
The CS comes after the US
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Which pairing procedure works best forcreating learning?
Given our notion that classicalconditioning establishes signals or cuesfor important future events, which
procedures might be best? Whichworst?
Think of the rattle snake.
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Which pairing works best?
All things being equal, delayed
conditioning is most effective.
Followed very closely by traceconditioning.
Simultaneous conditioning is weak. Backward conditioning is the weakest,
almost impossible.
Why are the last two so ineffective?
They do not signal what is coming up.
One of Pavlovs students found that when the smell of vanilla (CS) came
before the US (acid in the mouth), conditioning of salivation occurred in 20
trials. But when the smell came after the US, conditioning did not occur evenafter 427 pairings (after which he gave up).
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Another Factor: CS-USContiguity Contiguitycloseness in time between
two events.
In classical conditioning, CS-US
contiguity refers to the interval of timebetween the CS and US.
This time is called the InterstimulusInterval (ISI) Defined differently for trace and delayed
conditioning.
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CS-US Contiguity
Interstimulus Interval (ISI)
Interstimulus Interval (ISI)
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Delay ConditioningShort-Delay
US begins shortly (a second or less) after the CS begins.
Long-Delay
US begins several seconds or minutes after the CSbegins.
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CS-US Contiguity
In general, the shorter the ISI, thequicker the learning.
With simultaneous conditioning, in
which there is no interval at all, learningis very slow.
Rule of Thumb: Make the interval as
short as possible, just short ofsimultaneous presentations. NB: This rule of thumb has many
exceptions, depending on the species of
organism, the kind of response being
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Another Factor: Contingency Contingency is related to prediction
does one event, A, predict anotherevent, B If A, then B
In classical conditioning, it has to dowith the consistency of pairing CS andUS. If CS, then US (follows)
If the CS is always followed by US, youhave perfect contingency.
But what if the CS is followed by the US
inconsistently?
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Contingency: Rescorla (1968) Rats
Shock (US) Fear (UR)
CS = Tone
Three conditions CS presented without US 10% of time 20% of time
40% of time
Results:
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Contingency: Rescorla (1968)
Greater contingency,
More learning
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Stimulus Features
Almost any stimulus that can be detectedcan become a CS, but some are moreconditionable than others.
Compound Stimuli Studies of Pavlov
Two or more CSs presented at the same time justbefore the US is presented. [Tone & Light] : Food Salivation
Each CS then tested individually
Often, only one of the stumuli shows strongconditioning
Overshadowing if one CS is more intense orsalient, the other CS may be ignored Strong light better than weak tone
Loud tone better than weak light
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Sensory Preconditioning Sensory preconditioning is another
example of stimuli influenced bycompound events.
Sensory Preconditioning- two stimulisuch as light and tone are repeatedly
presented together without the occurrenceof a US (preconditioning).
Later, only one of these stimuli(e.g., tone) is paired with a US
(e.g., a shock).Then other stimulus (light) is
tested for conditioning.
Even though the second stimulus (light)
was never directly associated with the US
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Prior Experience with CS & US
Suppose you present a CS (e.g., a tone)repeatedly all by itself (never with a US likefood or shock).
You then start pairing the CS with a US,
trying to establish conditioning. How will the conditioning compare to
standard procedures (where the CS isnt atfirst repeatedly presented alone)?
In general, learning is slower. Latent Inhibition: The repeated appearance
of the CS without the US seems to inhibitthe ability of the CS to elicit the conditioned
response.
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Latent Inhibition: the more pre-exposures of the CS without the US,
the slower the learning.
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Why does latent inhibitionoccur? Remember contingency effects: learning is
stronger when the CS predicts the UCS (IfCS, then US) a greater proportion of thetime.
In latent inhibition, there is no contingencyduring the initial pre-exposure period.
Basically, since the CS seems unrelated tothe US for a while, it takes more contingent
presentations (CS
US) before theorganism believes there is really arelationship.
A completely new stimulus is a better CS
than an older stimulus that didnt seem to
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Prior Experience:Blocking in Compound Stimulus Studies
Leon Kamin discovered that sometimesa new CS cannot be establishedeffectively.
This occurs when the new CS is part ofa compound stimulus study with apreviously established CS.
A picture is worth a thousand words.
K i
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KaminBlocking
1. Light is established as a CS for eliciting
salivation.
2. Now the light and a new CS (tone)
are presented together before the US, andthe compound stimulus elicits salivation.
3. Now test the original CS (light): it still
elicits salivation.
4. Now try the tone by itself: conditioning
does not occur.
The tone was blocked by the previous
conditioning of the light
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Blocking Blocking resembles overshadowing, in
which one CS in a compound stimulus getsovershadowed by another stronger or moresalient CS.
In overshadowing, both stimuli (CSs) in the
compound are new stimuli. But in blocking, one of the CSs is previously
established and is known to elicit the CR.
In blocking, the new CS often doesnt addanything more to the established CS inpredicting the US.
If an employee can predict the stock market
with 100% accuracy, would you hire
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Number of Pairings
Acquisition (learning) curve
Non-linear
Asymptote
Conditioning Trials
CRS
trength
asymptote
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Intertrial Interval The intertrial interval (ITI) is the time
between each CS-US pairing (i.e., betweentrials).
Recall that the shorter the interstimulusinterval (ISI), i.e., when the CS is closer tothe US in time, the better the learning.
But what about the interval between trials(ITI)? Is learning stronger when the time
between trials is brief or longer? Counter-intuitively, more time between
trials often produces better learning.
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Other Variables AffectingConditioning
Age: Older people do not condition as readily
as younger people.
Stress: People and other organisms condition
more readily when under stress.
Note: Stress hormones consolidate memories.
(e.g., flashbulb memories)
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Learning, then losing it:Extinction Continued pairing of CS (tone) with US
(food) maintains the CR (salivation),i.e., the learning is maintained.
Repeated presentation of the CS
without US leads to a weakening andstopping of the CR: this is calledExtinction of the CR.
Pavlovs data: After repeated trials of showing dogs food then
giving it to them, the mere sight of food eventually elicitssalivation.
But when food was shown to dogs repeatedly without giving
the food to them, then, over time, the sight of food no longer
produced salivation---the response was extinguished.
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Spontaneous Recovery After extinction, let time pass
Present CS again by itself
Temporary, small return of CR
i i i
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Reacquisition
Establish a CSCR connection.
Extinguish CR by presenting CS alone.
Try to establish the CSCR connectionagain.
Conditioning the second time around is
much quicker. Fewer trials requiredthan the original learning prior toextinction.
ll h
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All Together Now.
Trials/Time
Strength
of
CR
Acquisition ExtinctionSpontaneousRecovery Reacquisition
CS&US CS alone CS alone CS&US
Hi h O d C di i i
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Higher Order Conditioning Association of CS and US is First-Order
Conditioning However, CSs can be associated with other,
established CSs
Second-order conditioning
salivation (CR)
first-order CS
tone (CS1) food (US)
second-order CS
Light (CS2)
Hi h O d C diti i
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Higher Order Conditioning Among humans, language is saturated with
higher order conditioning.
Staats & Staats (1957) Students observe non-sense syllables on a screen
(e.g., Laj, Qug, Yof, etc).
At the same time, Ss also repeat words spoken bythe experimenter. Sometimes repeated positive words (joy, peace,
love).
Sometimes repeated negative words (sad, thief,
foe) No natural US involved, just words
Students then rated nonsense syllables on a scalefrom pleasant to unpleasant.
Students rated the nonsense according to the
words with which they had been paired.Politics and Advertising
Th i f Cl i l
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Theories of ClassicalConditioning Substitution Theory (Pavlov)
The conditioned stimulus becomes a substitutefor the unconditioned stimulus
Learning depends only the number ofconditioned/unconditioned stimulus pairings
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Pavlov believed that conditioningdepended only on temporal contiguity:
(c)At the start of conditioning, activity in
the UCS center automatically causesactivation of the UCR center. At this timeactivity of the CS center does not affectthe UCS center.
(d)(b) After sufficient pairings of the CSand UCS, their simultaneous activitycauses the growth of a connectionbetween the CS and UCS centers.
Afterward, activity in the CS center willflow to the UCS center and thereforeexcite the UCR center.
Pavlovs Substitution Theory
P bl ith S b tit ti
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Problems with SubstitutionTheory If substitution of CS for US is what is
really happening, then UR should bevery similar to CR
A lot of time, this does happen, but not
always Sometimes, UR and CR look different
Also, stimulus substitution theoryassumes that simple contiguity(repeated pairing of CS and US)
establishes conditioning.
Sit ti h Sti l
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Situation where Stimulus-Substitution does not explain
events
Jump (UR) Freeze (CR)
Shock (US) Jump, freeze, +heart rate (UR)
Tone: Shock (US) Jump, freeze, +heart rate (UR)
Tone (CS) Freeze only, -heart rate (CR)If the CR differs from the UR,
simple substitution does not
seem to be the full story.
Rescorla Wagner Model: A
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Rescorla-Wagner Model: AMathematical Model of Classical
Conditioning Proposes that there is a limit to how muchlearning can occur through the pairing of aCS and US.
A CS acquires a limited amount of
associative strength on each trial (drawnfrom the limited pool available).
Associative strength amount of learning. Notation: V = associative strength
Maximum associative strength Notation: = Vmax = Upper limit of associative
strength (V)
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V and Vmax ()
Trials
0 2 4 6 8 10
AssociativeStrength
0
2
4
6
8
10
VMAX
Si=0.25
VMAX=10.00
VSUM= 0.00
J
=
V
Th R W ti f i l
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The R-W equation for a singleCS Vnn = c( Vn-1)
Vnn = amount of change in associative strength= amount of change in associative strengthon trial non trial n
Vn-1 = associative strength on the previous trial
= Vmax = maximum possible associativestrength
c = salience/intensity of the CS (varies from 0-1, with higher values meaning greater
salience/intensity).
Using this equation, we can plot V (associative
strength) acquired at each trial, which gives a
V i (i V )
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Varying (i.e., Vmax)
c = .50
= 100
c = .50
= 65
R W:Varying c (i e
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R-W:Varying c (i.e.,salience/intensity)
c = .10
= 100
c = .50
= 100
Higher salience, faster learning
Extinction of a CS
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Extinction of a CS
c = .30 = 100
US always follows CS
c=.30
= 100
Beginning with trial 10,
CS presented without US(like a bell without food)
R W and Contingency
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R-W and Contingency
c = .30
= 100US always follows CS
c = .30
= 100
US only sometimes follows CS
Note that learning is slower
never reaches = 100 over same
number of trials.
R W and compound stimuli
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R-W and compound stimuli
Competitive learning: The total learningavailable, , must be shared by eachstimulus in a compound. Thus, the amount
of learning to each stimulus is less in acompound than if that stimulus is alone.
R W and Compound Stimuli:
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R-W and Compound Stimuli:OvershadowingTwo stimuli, a tone (CS1) and a light (CS2), presented simultaneously over all trials.
c 1= .25
c 2 =.25
= 100
same salience
c 1= .25
c 2 =.10 = 100
The more salient stimulus overshadows the other.
R W and Blocking
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R-W and Blockingc 1= .25
c 2 =.25
= 100
same salience;
Both CSs present on all trials
c 1= .25
c 2 =.25
= 100
same salience;
CS1 by itself for six trials
Then both CS present thereafter
So, when one CS established first,
it blocks the second from becoming
established
Rescorla Wagner
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Rescorla-Wagner Good mathematical model, accounting
for Nonlinear learning curves with upper limit
Salience/intensity of CS
Extinction
Contingency
Overshadowing
Blocking
But, doesnt account for CS-US contiguity (time between CS and US)
Latent Inhibition
Spontaneous Recovery