Aversive Control:

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Chapter 10

• Aversive Control
• Avoidance and Punishment

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Instrumental Conditioning Procedures
Positive Reinforcement
Punishment
Response increases
Response decreases
Omission Training
Negative Reinforcement
Response decreases
Response increases
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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

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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
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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
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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

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Brogden, Lipman, Culler (1938)
Results Figure 10.2
These results showed that avoidance conditioning
is different than standard classical conditioning
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The Discriminated Avoidance Procedure
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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).
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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)

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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?
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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)
US (shock)
UR (fear)
CR (fear)
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The Two-Process Theory of Avoidance
Now, the subject can be negatively reinforced
during the warning stimulus this is the second,
operant conditioning process
Removes
R
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.
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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)?
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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

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Brown Jacobs (1949)
Results Figure 10.6
Organisms do learn to escape from the CS,
supporting the Two-Process Theory of Avoidance.
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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
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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

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Kamin, Brimer, Black (1963)
Results figure 10.7
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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
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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

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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
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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?