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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Step 2: Selection

“Bell”Neutral Stimulus or

Conditioned Stimulus (CS)

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Weak AcidUS

SalivationUR

BellCS

Step 3: Training

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Step 4: Acquisition

BellCS

SalivationCR

http://www.youtube.com/watch?v=CpoLxEN54ho

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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.

http://www.youtube.com/watch?v=CpoLxEN54ho

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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

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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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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.


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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.


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US (weak acid) UR (Salivation)

CS (2kHz 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 (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


CS(Tone) Weaker brain activityAuditory

Area

USAcid

CR(No

Salivation)


TemporaryConnection(inhibition)

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Brain

Generalization (Irradiation)

Medulla


CS(2kHz Tone)


Area

US(Acid)

CR(Salivation)


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


CS (1kHz Tone)


Area

US (Acid)

CR(Salivation)


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

ent

E

I

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 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

ng

Res

po

nse

Wea

kR

esp

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US(Weak Acid)

CR (Salivation)

CSsLight (medium) + Tone (high)


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


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.

ivan petrovich pavlov - henderson state universityfac.hsu.edu/ahmada/3 courses/2 learning/learning...

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