Chapter 8 Avoidance and Punishment
Negative Reinforcement: A behavior strengthening procedure in which an aversive stimulus is
removed or omitted if the behavior occurs. For example, an individual takes a Tylenol, and this is
followed by the termination of a headache. In this case, the individual escapes from the pain of the
headache by performing some behavior. As a result, this behavior should be strengthened in the
future: the next time the person has a headache, he is likely to take a Tylenol again.
The term Negative Reinforcement also includes instances of Avoidance in which a response
prevents an unpleasant stimulus (aversive stimulus) from occurring in the first place. For example,
paying your income tax avoids the unpleasant consequences of failing to do so.
The term positive indicates that a stimulus is presented if a behavior occurs; the term negative
indicates that stimulus is removed or avoided entirely if a behavior occurs.
Punishment is a behavior reduction procedure which followed by an unpleasant stimulus.
Negative Punishment (Omission) is a behavior in which a pleasant stimulus is removed or omitted
if a behavior occurs. For example, a parent refuses to give a child her usual weekly allowance after
the child has performed some undesirable behavior (such as staying out too late).
●A representative experiment
The subjects were dogs and their apparatus was a shuttle box – a chamber with two
rectangular compartments separated by a barrier several inches high.
For the first few trails a typical dog’s responses were escape responses that is the dog
did not jump over the barrier until the shock has started.
After a few trails, a dog would making avoidance response that is it would start jump
over the barrier soon after the light went out, and if it jumped in less than 10 seconds it
did not receive the shock.
Avoidance paradox: The puzzle about How can the nonoccurrence of an aversive
event (shock) serve as a reinforcer for the avoidance response?
Explaining escape response: the response produced a change in an important stimulus.
E.g. shock changed to no shock when the escape response was made.
Reinforcement theorists have problems with explaining avoidance response.
Two-Factor theory: both of classical conditioning (learn to fear a stimulus) and
operant conditioning (escape from the fear-eliciting stimulus) are necessary for
avoidance response to occur. In Solomon and Wynne’s experience, the UR to shock is
fear, and fear plays a critical role in this theory.
Through classical conditioning, this fear response is transfer from the US (shock) to
some CS (a stimulus that precedes the shock, e.g. 10 seconds of darkness). This
conditioning of a fear response to an initially neutral stimulus is the first process of the
The second factor, based on operant conditioning, is escape from a fear-provoking CS
(darkness), but not the avoidance of shock.
●Evidence Supporting Two-Factor Theory
The role of the fear-eliciting CS is crucial to two-factor theory.
How CSs can influence avoidance behavior:
Example 1. : Trained dog in a shuttle box where jumping into the other compartment
postponed a shock. This result shows that a stimulus that is specifically trained as a CS
for fear can amplify ongoing avoidance behavior.
Example 2: This experiment attempts to turn a white compartment into an aversive
stimulus by shocking rats while they were in that chamber. From this point on, no
further shocks were presented, but Miller found that a rat would learn a new response,
turning a wheel when this response opened a door and allowed the rat to escape from
the white chamber. In the next phase, wheel turning was no longer an effective
response; instead a subject could escape from the white chamber by pressing a lever.
Eventually, the subject learned this second novel response. It shows the signal for the
shock in a typical avoidance situation does develop aversive properties, and that
animals can learn a new response that terminates the signal.
Miller: “ Trial and Error”
These studies support for two-factor theory by showing that a CS for shock can
accelerate ongoing avoidance behavior, and its removal can be used as a reinforcer
to teach an animal new response.
●Problem with Two-Factor Theory
A) Avoidance without observable signs of fear.
B) Extinction of avoidance behavior. From the perspective of two-factor theory, each
trail on which the shock is avoided is a classical conditioning extinction trial: the
CS(darkness) is presented, the CR of fear(or aversive) should gradually weaken on such
extinction trials until it is no longer elicited by the CS. But if the darkness no longer
elicits fear or aversion, the avoidance response should not occur. Thus, the theory
predicts that avoidance responding should gradually deteriorate after a series of trials
The evidences suggest that the strength of avoidance response was increasing not
decreasing during these shock-free trails.
It states that the classical conditioning component of two-factor theory is not
necessary. There is no need to assume that escape from a fear-eliciting CS is the
reinforcer for an avoidance response because avoidance of a shock can in itself serve as
Sidman – Avoidance Task or Free-operant Avoidance. In this procedure, there is no
signal preceding shock, but if the subject makes no response, the shocks occur.
If there is no CS to elicit fear or aversion, why would an avoidance response occur?
The answer is that although Sidman provide no external stimulus, the passage of time
could serve as a stimulus because the shocks occurred at regular interval. That is, once a
subject was familiar with the procedure, fear might increase as more and more time