Transcript Lecture 7 - Classical Conditioning

IVAN PAVLOV
1847 - 1936
The Adventures of the Black Girl
in Her Search for God
George Bernard Shaw (1933)
“What am I running away from? I’m not afraid of that dear noisy
old man.”
“Your fears and hopes are only fancies” said a voice close to her,
proceeding from a very shortsighted elderly man in spectacles
who was sitting on a gnarled log. “In running away you were
acting on a conditioned reflex. It is quite simple. Having lived
among lions you have from your childhood associated the sound
of a roar with deadly danger. Hence your precipitate flight
when that superstitious old jackass brayed at you. This
remarkable discovery cost me twenty-five years of devoted
research, during which I cut out the brains of innumerable
dogs, and observed their spittle by making holes in their cheeks
for them to salivate through instead of through their tongues.
The whole scientific world is prostrate at my feet in admiration
of this colossal achievement and gratitude for the light is has
shed on the great problems of human conduct.”
“Why didn’t you ask me?” said the black girl. “I could have told you in
twenty-five seconds without hurting those poor dogs.”
The Adventures of the Black Girl
in Her Search for God
George Bernard Shaw (1933)
“Your ignorance and presumption are unspeakable” said the old myop.
“The fact was known of course to every child; but it had never been
proved experimentally in the laboratory; and therefore it was not
scientifically known at all. It reached me as an unskilled conjecture: I
handed it on as science. Have you ever performed an experiment, may I
ask?”
“Several” said the black girl. “I will perform one now. Do you know what
you are sitting on?”
“I am sitting on a log grey with age, and covered with an uncomfortable
rugged bark” said the myop.
“You are mistaken” said the black girl. “You are sitting on a sleepy
crocodile.”
With a yell which Micah himself might have envied, the myop rose and fled
frantically to a neighboring tree, up which he climbed catlike with an
agility which in so elderly a gentleman was quite superhuman.
“Come down” said the black girl. “You ought to know that crocodiles are
only to be found near rivers. I was only trying an experiment. Come
down.”
Pavlov's significance:
• First empirical model of associationism.
• Integrated traditions of reflexology and associationism
• Recognized significance of psychic secretion.
• Provided basis for investigating neuroscience of classical
conditioning (Kandel)
• Defined modern concepts of conditioning.
Classical Conditioning
(Basic Phenomena)
• Acquisition
• Extinction
• Spontaneous recovery
• Higher order conditioning
• Discrimination
– Experimental neurosis
• Generalization
– Mediated generalization
Categories of Behavior
Voluntary
or operant
Unconditioned
Conditioned
•Looking
•Reading
•Babbling
•Writing
•Crawling
•Pupil response
•Fence jumping
•GSR when
telling a lie
Involuntary
or
•GSR response
respondent
Pavlov’s apparatus for studying
conditioned salivary response
Classical Conditioning
Before Training
US(food in mouth)
CS (bell)
UR (salivation)
No relevant response
Training
CS (tone) + US (food in mouth)
After Training (conditioning)
CS (tone)
CR
(salivation)
Development of a Conditioned Reflex
CS
US
Drops of
Saliva
CS
US
Drops of
Saliva
CS
US
Drops of
Saliva
ACQUISITION OF CONDITIONED SALIVARY RESPONSE
70
DROPS OF SALIVA
60
50
40
30
20
(PAVLOV, 1927)
10
0
0
10
20
30
40
NUMBER OF PAIRINGS OF CS & US
50
ACQUISITION OF CONDITIONED RESPONSE
20
LATENCY OF CR (SEC.)
18
16
14
(PAVLOV, 1927)
12
10
8
6
4
2
0
10
20
30
40
50
NUMBER OF PAIRINGS OF CS AND US
Unconditional Stimulus (US)
•The stimulus in a classical conditioning experiment that
elicits the unconditional response.
Unconditional Response (UR)
•The response in a classical conditioning experiment that
is elicited by the unconditional stimulus.
Conditional Stimulus (CS)
•The stimulus in a classical conditioning experiment that
is neutral with respect to the unconditional response.
Conditional Response (CR)
•The response in a classical conditioning experiment that
is elicited by the conditional stimulus.
Unconditional reflex:
UCS
UCR
Drilling
Pain
Conditional reflex:
CS
Sound of drill
CR
Pain
Temporal Relationships Between
CS & US
On
Delay
Trace
CS
Off
US
US
CS
US
Simultaneous
CS
Backward CS
US
EXTINCTION
Trial 1:
CS
CR
US
Later Trials:
Simultaneous Recording of Multiple CRs
Simultaneous Recording of Multiple CRs
EXTINCTION OF CONDITIONED SALIVARY RESPONSE
70
DROPS OF SALIVA
60
50
(PAVLOV, 1927)
40
30
20
10
0
0
10
20
30
40
50
NUMBER OF UNPAIRED PRESENTATIONS OF CS
DISCRIMINATION LEARNING:
CS+ alternates with CSe.g., Buzzer  Food (Acquisition)
Light  No Food (Extinction)
• Initial generalization from CS+ to CS
• Gradual weakening of response to CS
• Subject responds mainly to CS+ at the end
of discrimination training
Establishing an “EXPERIMENTAL NEUROSIS”
S+
S16:8
Initial
Discrimination
14:8
12:8
10:8
9:8
Final
Discrimination
GENERALIZATION OF CR
90
% MAGNITUDE OF CR
80
70
60
50
40
30
20
(PAVLOV, 1927)
10
0
400
800
1200
1800
FREQUENCY [Hz]
200
Establishing Higher Order Conditioning
Stage 1
Bell (CS1)
Food (US)
Light (CS2)
Bell (CS1)
Salivation (CR)
Salivation (CR)
No Salivation
Salivation (CR)
Stage 2
Light (CS2)
Bell (CS1)
Stage 3
Buzzer (CS3)
Light (CS2)
Buzzer (CS3)
salivation (CR2)
salivation (CR1)
no salivation
salivation (CR2)
salivation
Taste Aversion
US (stomach flu)
 UR (nausea)
CS (taste of sauce)
+
 UR (nausea)
US (flu)
CS (taste of sauce)  CR (nausea)
Advertising
US (popular tune)  UR (good feeling)
CS (product)
+
 UR (good feeling)
US (popular tune)
CS (product)
 CR (good feeling)
Conditioned Fear
(Phobia)
US (noise)
 UR (fear)
CS (rabbit)
+
US (noise)
 UR (fear)
CS (rabbit)
 CR (fear)
Counterconditioning
(desensitization)
CS (rabbit)
US (milk)
 CR (fear)
 UR (pleasant feeling)
CS (rabbit)
+
US (milk)
 UR (pleasant feeling
US (rabbit)
 CR (pleasant feeling)
Counter conditioning:
QuickTime™ and a TIFF (LZW) decompressor are needed to see this pi cture.
QuickTime™ and a TIFF (LZW) decompressor are needed to see this pi cture.
CONDITIONING
Trial 1:
CS
(Bell)
CR
(Salivation)
US
(Food)
UR
(Salivation)
Later Trials:
Classical Conditioning (Type S)
Signal a reinforcing event (an unconditioned stimulus “US”), e.g.,
sound a buzzer (a conditioned stimulus) before delivering food.
Buzzer  food
CS  US
Initially,
US  UR
food  salivation
CS  orienting (?)
buzzer  turning towards source
no salivation (or minimal salivation)
After multiple pairings of CS and US:
CS  CR
buzzer  salivation