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Transcript of Ivan Petrovich Pavlov - Henderson State Universityfac.hsu.edu/ahmada/3 Courses/2 Learning/Learning...
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Ivan Petrovich Pavlov(1849-1936)
Chapter 7
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Ivan Petrovich Pavlov
(1849-1936)
http
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1. Born in Ryazan, Russia on Sep 14, 1849.
2. Studied the digestive system and won the Nobel Prize in 1904 for physiology and medicine.
3. At age 50 discovered classical conditioning.
Nobel Prize Seal
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Salivary Reflex
TongueReceptors
Glossopharyngeal Nerve (sensory)
Medulla
WeakAcid
Salivationin mouth
Parotid ductreleases watery
saliva
Dilates blood vesselsin parotid gland
Glossopharyngeal Nerve (motor)
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Experimental Setup
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Classical Conditioning
Weak AcidUnconditionedStimulus (US)
SalivationUnconditionedResponse (UR)
Step 1: Reflex
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Classical Conditioning
Step 2: Selection
“Bell”Neutral Stimulus or
Conditioned Stimulus (CS)
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Classical Conditioning
Weak AcidUS
SalivationUR
BellCS
Step 3: Training
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Classical Conditioning
Step 4: Acquisition
BellCS
SalivationCR
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Features of Classical Conditioning
1. Pavlov suggested that an association builds between CS-CR after conditioning takes place (psychic reflex).
2. CR (saliva) is similar to UR (saliva), however magnitude (quantity of saliva) for CR is lesser than UR.
3. For optimal conditioning to take place CS needed to occur ½ second before US.
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History of Classical Conditioning
1. The concept of conditioning was suggested in 1751 by Robert Whytt, but no one was interested in the idea.
2. In 1902, E. B. Twitmyer reported knee-jerk reflex based on a similar association between bell and knee-jerk response.
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Extinction
US (Weak Acid)CS(Bell)
CR(Salivation)
1. CR (salivation) extinguishes if US (weak acid) is removed.
2. Thus US (weak acid) serves as reinforcement.
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Extinction
-2
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Trial
CR
(S
aliva, m
l)
US
Removed
CR
Extingushed
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1. After extinction of CR (salivation) a rest period “spontaneously” recovers the CR.
2. CR during spontaneous recovery, has a lower magnitude than UR and extinguishes rapidly if not reinforced with a US.
Spontaneous Recovery
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Spontaneous Recovery
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2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Trial
CR
(S
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CR
Extingushed
Spontaneous
Recovery
Rest
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CS (Bell) CR (Salivation)
US (weak acid) UR (Salivation)
First-order conditioning
CS2 (Buzzer) CR (Salivation)Second-order conditioning
CS3 (Tone) CR (Salivation)Third-order conditioning
Higher-order Conditioning
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During conditioning a CS can develop reinforcing properties (secondary reinforcer), and can be used in place of a US (primary reinforcer) to condition a
second CS. This second CS can then be used to condition a third CS, and so on. Second and third-
order conditioning are called higher-order conditioning.
Higher-order Conditioning
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1. Magnitude of CR (salivation) decreases with each successive ordered conditioning.
2. Extinction is faster for higher-ordered conditioned responses.
3. Higher-order conditioning is a complex form of learning.
Higher-order Conditioning
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US (weak acid) UR (Salivation)
CS (2kHz Tone) CR (Salivation)
CS (1kHz Tone) CR (Salivation)
CS (3kHz Tone) CR (Salivation)
Generalization refers to increased capability of producing a CR by stimuli that are similar to the first
CS that lead to conditioning.
Generalization
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Generalization Gradient
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0.5 1.0 1.5 2.0 2.5 3.0 3.5
Tone Intensity (kHz)
CR (S
aliv
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Fear Generalized
After conditioned fear of the white furry rat was inculcated in “Little Albert,” he was afraid of other
stimuli that resembled the white rat, like a furry rabbit, a dog, or a Santa Claus mask, etc., (Watson
& Rayner, 1920).
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1. Magnitude of CR (salivation) is lower to CSs other than the first CS (2kHz tone).
2. Responses extinguish faster to CSs other than the first CS (2kHz tone).
Generalization
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CS (2kHz Tone) CR (Salivation)
CS (1kHz Tone) CR (No Salivation)
You can train animals to discriminate between two CSs, such that CR to one CS is different from the
other.
US (weak acid)
No weak acid
Discrimination
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Discrimination Training
1. Repetition: Many CS-US pairing that lead to a specific CR.
2. Selection: Among many CS only one CS reinforced with US to generate a CR.
3. Discrimination precedes generalization. With successive training the two CSs lead to different (discriminate) CRs.
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CS-US Relationship
USCS
CSUS
CSUS
CSUS
ShockTone
Forward Conditioning
Delayed Conditioning
Simultaneous Conditioning
Backward Conditioning
Strongconditioning
Weak/Noconditioning
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Physiological Basis of Conditioning
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Brain
Physiology of Conditioning
Medulla
Dominant brain activity
CS(Tone)
Weaker brain activityAuditory
Area
US(Acid)
UR/CR(Salivation)
NeighboringCNS areas
TemporaryConnection(excitation)
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Brain
Extinction
Medulla
Dominant brain activity
CS(Tone) Weaker brain activityAuditory
Area
USAcid
CR(No
Salivation)
NeighboringCNS areas
TemporaryConnection(inhibition)
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Brain
Generalization (Irradiation)
Medulla
Dominant brain activity
CS(2kHz Tone)
Weaker brain activityAuditory
Area
US(Acid)
CR(Salivation)
NeighboringCNS areas
CS(1kHz Tone)
CS(3kHz Tone)
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Irradiation
Pavlov described irradiation as the physiological process that took place during generalization. The
conditioned brain area irradiated (spilled) over other brain areas permitting similar CSs to elicit CR.
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Brain
Discrimination: Concentration
Medulla
Dominant brain activity
CS (1kHz Tone)
Weaker brain activityAuditory
Area
US (Acid)
CR(Salivation)
NeighboringCNS areas
CS (2kHz Tone)
CR(No Salivation)
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Concentration
Two CSs (or more) can be associated with two kinds of CRs. CSs discriminate across CRs because they
excite non-overlapping areas (concentration) in the brain. Thus one CS results in one kind of CR
(salivation) and the other CS in another kind of CR (no salivation).
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Excitatory Conditioning
US(Weak Acid)
UR(Salivation)
CS(Bell)
Excitatory conditioning occurs when a CS (bell) gets associated with occurrence of US (weak acid). Thus
CS excites a CR.
CS(Bell)
CR(Salivation)
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Inhibitory Conditioning
US(Air Puff)
CR(Eye Blink)
CS(Tone)
US(No Air Puff)
CR(No Eye Blink)
CSs(Tone + Light)
CR(No Eye Blink)
CS(Light)
Inhibitory conditioning occurs when a CS (light) gets associated with absence of US (no air puff), and
does not elicit a CR (eye blink).
Phase I: Acquisition
Phase II: Testing
Inte
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Excitation & Inhibition
Excitation and inhibition govern all central nervous system (CNS) activities caused by environmental
events.
Pavlov often talked about Janus, the Roman god with two faces in opposite directions. These opposing faces related to excitation
and inhibition, as two opposing processes in the nervous activity (Babkin, 1949).
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Cortical Mosaic
This excitatory and inhibitory activity in the brain forms a cortical mosaic. Momentary cortical mosaic
determines how an organism will respond to its environment at a given moment, and Dynamic
Stereotype is a stable cortical mosaic.
E
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Brain
Enviro
nm
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E
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Brain
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Compound Conditioning
When two CSs of equal strength are used together to conditioned a response, the CR is strong. When
these CSs are then tested separately they both produce moderate responses.
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Compound Conditioning
US(Weak Acid)
CR (Salivation)
CSsLight (medium) + Tone (medium)
CR(Salivation)
CR(Salivation)
CSTone (medium)
CSLight (medium)
Phase I: Acquisition
Phase II: Testing
CR (Salivation)
CSsLight (medium) + Tone (medium)
StrongResponse
ModerateResponses
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Overshadowing
In overshadowing one CS is more salient (high tone) than the other (low light). Thus tone elicits a
stronger CR than light (Pavlov, 1927).
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Overshadowing
CR(Salivation)
CR(Salivation)
CSTone (medium)
CSLight (medium)
Phase II: Testing
Stro
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Res
po
nse
Wea
kR
esp
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se
US(Weak Acid)
CR (Salivation)
CSsLight (medium) + Tone (high)
Phase I: Acquisition
CR (Salivation)
CSsLight (medium) + Tone (high)
StrongResponse
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Blocking
Blocking involves conditioning a tone (CS) to elicit a CR (Fear; Kamin, 1969) through shock (US). When the tone reliably elicits the CR; tone is paired with another CS (light) as a compound stimulus to elicit CR. When the light and the tone are then tested
separately… it is the tone that elicits a stronger CR (fear) and not light. So the tone blocks the light CS.
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Blocking
US(Shock)
CR(Fear)
CSsTone (medium) + Light (medium)
CR(Fear)
CSTone (Medium)
CSLight (Medium)
US(Shock)
CR(Fear)
CSTone (medium)
Phase I: Prior Conditioning
Phase II: Acquisition
CR(Fear)
Phase III: Testing
Stro
ng
Res
po
nse
Wea
kR
esp
on
se
StrongResponse
StrongResponse
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Overexpectation
When two CSs have been paired separately with the US and then together, both protocols produce
strong association. When the two CSs are tested later separately produce a moderate response. This
is called overexpectation.
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Overexpectation
CR(Fear)
CSsTone (medium) + Light (medium)
CR(Fear)
CSTone (Medium)
CSLight (Medium)
US(Shock)
CR(Fear)
CSTone (medium)
Phase I: Prior Conditioning
Phase II: Compound Stimuli
CR(Fear)
Phase III: Testing
US(Shock)
CR(Fear)
CSLight (medium)
Stro
ng
Res
po
nse
s
ModerateResponses
Stro
ng
Res
po
nse
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Signal Systems
Pavlov’s work introduced stimulation in the context of future behavior. And therefore suggested that CS
preceded as a signal to biologically significant events.
Signal
US(Weak Acid)
UR
(Salivation)CS
(Bell)
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Types of Signals
Events that evoke biological responses are termed as first signal system. Symbols that represent these events and lead to biological responses are called
second signal system or “signals of signals.”
Signal System Stimulus Response
First signals See a lion You sweat
Second signals Hear the word “lion” You sweat
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Other Ideas about Classical Conditioning
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Contingency
Kamin’s (1969) blocking effect and surprisingness hypothesis lead Rescorla & Wagner (1966, 1972) to
propose that classical conditioning relied on contingency between CS and US.
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Rescorla-Wagner Model
1. Dogs jump the hurdle in the shuttle box to avoid the shock which comes after 30 seconds. Dogs jump based on their own mental clocks.
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Contingency
2. Dogs were taken out of shuttle box and were put into three contingency groups (CS-US pairing).
Contingency
Positive Negative No
CS-US
(tone comes before shock)
US-CS
(tone comes after shock)
CS/US
(tone-shock follow each other randomly)
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Training
3. Dogs were put back in the shuttle box and trained to avoid the shock with tone as the CS.
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Results
Contingency
Positive Negative No
Rate of responding increased
Rate of responding decreased
Rate of responding
same as baseline
Tone Precedes Shock
Rat
e o
f R
esp
on
din
g
Tone Follows Shock Tone/Shock Random
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Contingency
Tone (T)
Shock (S)
T T T T TT
S S S S SS
Tone (T)
Shock (S)
T T T
S S S
Little or no conditioning
Strong conditioning
Rescorla & Wagner (1966, 1972) thus suggested that a contingency exists between CS and US to
cause conditioning and not to CS-US contiguity as proposed by Pavlov (1927).
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Learned Helplessness
Seligman et al., (1969, 1975) argued that the animals do
learn a state of helplessness in Rescorla’s, No Contingencygroup. The group loses its
relevance (learned irrelevance) to CS. Whenever a US is paired
with this CS, its efficacy is diminished.
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Superconditioning
1. Concept of CS-US relevancebecame important in aversive conditioning. Naturally it was food that got associated with illness and not the plate in which it was served. Certain CS belongwith US.
2. Conditioning is possible with longer time interval between CS and the US. (Garcia, 1960s). John Garcia (1917-Present)
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Taste Aversion
Rats like drinking saccharine water. Garcia & Koelling (1966) used light, tone and taste
(saccharine water) as compound CS. They called it the “bright-noisy-tasty” water.
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Aversive Conditioning
Phase II: Testing
US(Shock)
CR (Fear)
CSsLight + Tone + Taste
Phase I: Acquisition
US(Drug)
CR (Fear)
CSsLight + Tone + Taste
CR (Fear light and tone but drink saccharine water)
CSsLight or Tone
Group 1
Group 2
Group 1
CSsLight or Tone
Group 2CR
(Fear light and tone and NOT drink saccharine water)
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Taste Aversion: Garcia Effect
1. Some CSs are biologically relevant (or belong to) US.
2. Time delay between CS and the US can be very long (up to hours) unlike observed in other forms of classical conditioning.
3. Only a few presentation (sometime one) are enough to bond CS with US.
4. Taste aversions are resistant to extinction.
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Clinical Applications
1. Extinction: Unwanted habits can be eliminated through the process of extinction. If US is withdrawn the CR will extinguish after some time. When mother ignores the toddler’s tantrum, whining behaviors fades.
2. Counter-conditioning: CS is paired with a noxious US to counter the original CS-US strength. Smoking (pleasure) replaced with anectine (threat) to quit smoking.
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Clinical Applications
3. Flooding: Sustained presence of the US abolishes an undesired response like a phobia. The individual is forced to stay with the fear inducing stimulus only to learn that it is not threatening.
4. Systematic Desensitization: A gradual process of diminishing phobias and fears with the introduction of relaxation using a hierarchy of fear inducing stimuli.
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Pavlov Institute of PhysiologyRussian Academy of Sciences
http://www.infran.ru/history_eng.htm
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Questions
Q9. How does Pavlov explain the physiological basis of stimulus generalization and discrimination?
Q10. Why does Rescorla say that classical conditioning occurs due to contingency between CS-US and not contiguity. Describe Rescorla (1966) study to elucidate this point.
Q11. Explain in detail compound conditioning. Include in your answer overshadowing, blocking and overexpectation.