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Chapter 10
Aversive Control:
Avoidance and Punishment
Instrumental Conditioning Procedures
Appetitive
Positive
Contingency
(R produces O)
Negative
Contingency
(R prevents O)
Positive
Reinforcement
Response increases
Omission
Training
Response decreases
Aversive
Punishment
Response decreases
Negative
Reinforcement
Response increases
Aversive Control
 Negative reinforcement – also called escape/avoidance
 Avoidance procedures increase the operant response
 Punishment procedures decrease the operant response
 With both types of procedures, the behavior that
develops serves to minimize contact with the aversive
stimulus
 Critical difference:
• in avoidance, taking a specific action prevents the
aversive stimulus
• in punishment, refraining from action minimizes
contact with the aversive stimulus
Aversive Control
Avoidance behavior is sometimes referred to as
active avoidance
Punishment is sometimes referred to as
passive avoidance
Both terms emphasize the fact that both avoidance
and punishment involve minimizing contact with an
aversive stimulus
Avoidance Behavior
 origins in Pavlovian conditioning
 first experiments conducted by Bechterev (1913)
Participants instructed to place a finger on a metal plate
A warning stimulus (CS) was then presented, followed by
a brief shock (US)
The participants quickly lifted their finger off the plate
after being shocked
After a few trials, they also learned to make the response
during the CS
This experiment viewed as a standard example of
Pavlovian conditioning
Avoidance Behavior
In the 1930s people focused on the difference between a standard
classical conditioning procedure and a procedure that had an
instrumental avoidance component added
Brogden, Lipman, & Culler (1938)
• Tested 2 groups of guinea pigs in a rotating wheel
• A tone served as the CS and a shock as the US
• The shock stimulated the animals to run and rotate the wheel
• For the classical conditioning group, the shock was presented 2 s
after the onset of the tone
• For the avoidance conditioning group, the shock also followed the
tone when the animals did not make the CR (a small movement of
the wheel)
• if the avoidance animals moved the wheel during the tone CS
before the shock occurred, the scheduled shock was omitted
Brogden, Lipman, & Culler (1938)
Results: Figure 10.2
Classical
Avoidance
100
80
Percentage 60
of CRs
40
20
Days
These results showed that avoidance conditioning is different than
standard classical conditioning
The Discriminated Avoidance Procedure
Avoidance Trial
Escape Trial
CS
CS
US
US
R
R
Discriminated, or Signalled, Avoidance
A warning stimulus (e.g., a light) signals a
forthcoming SAversive (e.g., a shock)
If the required response is made during the
light (warning stimulus), before the shock
(SAversive) occurs, the subject avoids the shock.
If a response is not made during the warning
stimulus of the light, the shock (SAversive) occurs,
and terminates when the required response is
made (i.e., escape).
Discriminated, or Signalled, Avoidance
Discriminated avoidance procedures are often conducted
in a shuttle box
 the shuttle box consists of 2 compartments separated
by a barrier
 the animal is placed on one side of the apparatus
 at the start of the trial, a CS is presented
 if the animal crosses to the other side before the shock
is presented, then no shock occurs and the CS goes off
 after the inter-trial interval, the next trial can be
started with the animal in the second compartment
 shuttle avoidance
 two-way shuttle avoidance or one-way shuttle
avoidance (one-way avoidance easier to learn)
The Two-Process Theory of Avoidance
Avoidance procedures involve a negative contingency
between a response and an aversive stimulus
The absence of the aversive stimulus is presumably the
reason that avoidance responses are made
But, how can the absence of something provide
reinforcement for instrumental behavior?
The Two-Process Theory of Avoidance
Explains avoidance learning in terms of two necessary
processes:
First, the subject learns to associate the warning
stimulus with the SAversive – what is this?
This is a classical conditioning process; the warning
stimulus of the light is the CS, the SAversive of shock is
the US.
CS (light)
CR (fear)
US (shock)
UR (fear)
The Two-Process Theory of Avoidance
Now, the subject can be negatively reinforced during
the warning stimulus; this is the second, operant
conditioning process
R
Removes
CS
i.e., reduces fear
Strengthens
Thus the two-process theory reduces avoidance
learning to escape learning; the organism learns to
escape from the CS and the fear that it elicits.
Support for Two-Process Theory of Avoidance
Acquired-Drive Experiments
In the typical avoidance procedure, classical conditioning
of fear and instrumental reinforcement through fear
reduction occur intermixed in a series of trial
If Two-Process theory is right, then separating the two
processes should still lead to successful learning.
Two phases to acquired-drive experiments:
First, classical conditioning to acquire fear of CS
Second, escape training with CS as SAversive; will
the subject learn a response to escape from just
the CS (i.e., US no longer presented)?
Acquired-Drive Experiment
Brown & Jacobs (1949)
 tested rats in a shuttle box
 in phase 1 (classical conditioning), rats confined to one side of
the apparatus and given 22 CS-shock pairings
 in phase 2 (instrumental conditioning), rats were placed on one
side of the apparatus with the center barrier removed
 the CS was presented and remained on until the rat turned it
off by crossing to the other side (no shocks presented)
 how long the rats took to cross the shuttle box and turn off the
CS was measured for each trial
Brown & Jacobs (1949)
Results: Figure 10.6
Control
Experimental
Latency
Trials
Organisms do learn to escape from the CS, supporting
the Two-Process Theory of Avoidance.
Evidence that questions the Two-Process
Theory of Avoidance
If fear motivates and reinforces avoidance responding,
then the conditioning of fear and the conditioning of
instrumental avoidance behavior should be highly
correlated
However, the level of fear is not always positively
correlated with avoidance
Animals often become less fearful as they become more
proficient in performing the avoidance response
Kamin, Brimer, & Black (1963)
If the warning signal in an avoidance procedure comes to elicit fear,
then presentation of that stimulus in a conditioned suppression
procedure should result in suppression of behavior
 Rats initially trained to bar-press for food
 rats then trained to avoid shock in response to an auditory CS
in a shuttle-box
 training was continued for separate groups until they avoided
the shock on 1, 3, 9 or 27 consecutive trials
 the animals were then returned to the Skinner box for bar
pressing
 the CS that had been used in the shuttle box was periodically
presented to see how much suppression of bar pressing it would
produce
Kamin, Brimer, & Black (1963)
Results: figure 10.7
0
-.05
Adjusted
suppression -.10
ratio
-.15
-.20
1
3
9
Avoidance criterion
27
Kamin, Brimer, & Black (1963)
With more extensive avoidance training, response
suppression declined
Animals trained until they avoided the shock on 27
consecutive trials showed less conditioned suppression
to the avoidance CS than those trained to a criterion
of 9 consecutive avoidances
This suggests that fear, as measured by conditioned
suppression, decreases during extended avoidance
training
However, this decrease in fear is not accompanied by a
decrease in the strength of the avoidance response
Asymptotic Avoidance performance
Two-process theory predicts that the strength of the avoidance
response should fluctuate in cycles
 when a successful avoidance response occurs, the shock is
omitted on that trial
 this is an extinction trial for the conditioned fear response
 repetition of the avoidance response (and thus the CS-alone
extinction trials) should lead to extinction of fear
 as the CS becomes extinguished, there will be less reinforcement
resulting from the reduction of fear, and the avoidance response
should also become extinguished
 however, when the shock is not avoided, the CS is paired with
the US
 this should reinstate fear to the CS and re-establish the potential
for reinforcement through fear reduction, thereby reconditioning
the avoidance response
Asymptotic Avoidance performance
Thus, two-process theory predicts that after initial
acquisition, the avoidance response will go through
cycles of extinction and re-acquisition
However, this does not always happen
Avoidance behavior can be very persistent
Free-operant avoidance
 also called nondiscriminated avoidance or
Sidman avoidance
 shock postponement procedure
 no warning signal
Rats given shocks according to a shock-shock
(SCS) interval (e.g., a shock every 5 s)
unless they make a response to delay the shock
according to a response-shock (RCS) interval
(e.g., 30 s).
Problem for two-process theory?