Download Operant Conditioning

Instrumental
Conditioning
Basic Procedures and Processes
Instrumental or Operant
Conditioning?
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These terms both refer to learned changes in
behavior that occur as a result of the consequences
of the behavior.
“Instrumental ” refers to the fact that the behavior is
instrumental in bringing about a given consequence.
“Operant” refers to the fact that the behavior
operates on the environment, that is, has an effect
there.
Which term you prefer to use will probably depend
on whether you use a discrete-trials or free-operant
methodology.
Discrete-Trials Procedures
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Organized as a series of learning trials
Start of each trial is under control of the experimenter, not
the animal.
Usually focus on group averages and statistical analysis.
Dependent variables: latency, speed, number of errors,
etc. as functions of trials and conditions.
Examples
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Thorndike’s puzzle-box experiments
Maze learning
Researchers using these procedures prefer the term
“instrumental conditioning.”
Straight Alley
Start Box
Goal Box
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Free-Operant Procedures
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Monitored behavior is free to
occur at any time; under the
control of the animal
Dependent variable usually the
frequency or probability of
response as functions of time
and conditions
Focus is on the individual subject
– averaging over subjects and
inferential statistics discouraged.
Technology pioneered by B. F.
Skinner
Researchers using these
procedures prefer the term
“operant conditioning.”
Rat in the operant
chamber above is free
to press the lever at any
time.
Operant Chamber (Rat Version)
Pigeon Chamber in SoundIsolation Box
Computer used
to arrange
contingencies
and collect data
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Cumulative Recorder
Clock drive moves paper
under pen at constant rate.
Pen moves across by a
small amount with each
response.
Slope of line
indicates rate of
responding.
Reading the Cumulative
Record
The pen moves up a notch with each response.
Consequently, the position of the pen at any moment
indicates the total or cumulative number of responses
produced up to that moment.
The pen resets to bottom when it reaches the top of the
graph, so that it stays on the paper.
The paper moves under the pen at a constant rate.
Tick-marks indicate reinforcer deliveries.
The slope of the line at any point indicates the rate of
responding. Zero rate generates a horizontal line.
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Some Definitions
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Operant
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Reinforcer
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Some well-specified behavioral act, such as pressing a
lever.
A consequence of a behavior that serves to “strengthen”
the behavior.
“Stronger” behavior is behavior that occurs more
frequently, with higher probability, with shorter latency.
Reinforcement
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The procedure of making a reinforcer consequent on the
occurrence of an operant.
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Basic Processes
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Acquisition
Extinction
Spontaneous recovery
from extinction
Generalization and
Discrimination
Acquisition
Each leverpress
delivers a
pellet of food
to the hungry
rat.
From Skinner (1938)
After a few presses
and pellet-deliveries,
responding
accelerates to a high
rate.
Extinction
Pellets were
no longer
delivered
following lever presses.
The rate of
responding
declined
toward zero.
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Spontaneous Recovery
Note jump in
rate at start of
session
Spontaneous recovery is observed
at the start of each new extinction
session after a period of rest.
Generalization/Discrimination
Generalization Gradient
S+
A pigeon received grain
for pecking a key while a
vertical line (S+) was
projected on the key.
Extinction was in effect
when S+ was absent.
Tests were conducted in
extinction while lines of
various angle were
projected on the key.
The Discriminative Stimulus
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A stimulus in the presence of which a response is
reinforced.
A stimulus that sets the occasion for a response.
Sometimes symbolized as SD or as S+
Behavior analysts refer to the “three-term
contingency” in which reinforcement of a response is
contingent upon the presence of S D
Explains why behavior reinforced in one context
does not become “stronger” in all contexts.
Equivalent to Thorndike’s “situation.”
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