Avoidance and Escape Learning

So far we have spoken mainly of positive reinforcement. But animals also respond in predictable ways to avoid punishment. The term aversive control is used to cover situations in which behavior is motivated by the threat of an unpleasant stimulus. There are two main categories of behavior under aversive control: avoidance behavior and escape behavior.

What is aversive control? What are the two main types?

Escape conditioning occurs when the animal learns to perform an operant to terminate an ongoing, aversive stimulus. It is a "get me out of here" or "shut this off" reaction, aimed at escape from pain or annoyance. The behavior that produces escape is negatively reinforced (reinforced by the elimination of the unpleasant stimulus).

For example, you could get a rat to jump off a platform into some water—which a rat is normally reluctant to do—by electrifying the top of the platform, giving the rat a mild shock. When the rat jumps off, it escapes the shock. If the platform is not electrified, and is the only place to rest from swimming, the rat will stay on the platform until it gets shocked. The jump is an escape behavior.

How can escape conditioning be converted into avoidance conditioning?

Escape conditioning is converted into avoidance conditioning by giving a signal before the aversive stimulus starts. If the animal receives acue or signal that an aversive stimulus is coming, then after one or two occurrences of the punishing stimulus the cue will trigger an avoidance behavior. This kind of learning occurs quickly and is very durable. For example, if you sounded a tone before you electrified the platform, after one or two trials the rat would respond to the tone by jumping into the water. It would not wait for the shock. This is a form of stimulus control, because it puts behavior under control of a stimulus, in this case the warning tone.

Why are avoidance behaviors so persistent?

Avoidance behaviors are incredibly persistent. This is true even when there is no longer anything to avoid. The reason is that an animal that performs an avoidance reaction never experiences the aversive stimulus. But it receives negative reinforcement in the form of relief. Because of this, avoidance behavior is self-reinforcing. It keeps going forever, because relief functions as a reinforcer even if the original threat is removed. In the preceding example, the rat will respond to the tone by jumping into the water hundreds of times, even if you turn off the shock generator and never use it again. Each time it jumps, it probably figures (in a rat way) that it has avoided the shock.

What was Solomon's shuttle-box experiment, and what point does it illustrate?

Psychologist Richard Solomon demonstrated persistence of avoidance behavior in his classic shuttle box experiment. In this research, Solomon placed a dog in a large cage with two chambers. A low wall separated the two chambers. When Solomon electrified the floor on one side, the dog jumped to the other side. This was escape conditioning because the dog emitted the behavior of jumping after it experienced the aversive stimulus (electric shock). If Solomon electrified the floor on the other side of the cage, the dog jumped back to the original side (which was no longer electrified).

To convert the situation into one of avoidance learning, Solomon arranged for a signal to occur before each shock. He used an audible tone. After he sounded the tone, he turned on the shock, and the dog jumped to the other side. Soon the dog jumped as soon as it heard the tone. The escape behavior turned into avoidance behavior.

Now Solomon turned off the shock generator. But he continued to sound the tone, and the dog continued to jump back and forth over the barrier from one side to the other, as many times as Solomon sounded the tone. The behavior never extinguished. No matter how many times this was repeated, the dog continued to jump. It never allowed itself to discover that the shock generator had been turned off.

In what sense is avoidance conditioning "self-reinforcing"?

This is an important pattern because something similar happens to humans. Avoidance behavior is self-reinforcing. Relief is the reinforcer, and relief occurs whether or not the threat is still present. Avoidance conditioning can go on forever, even if there is no longer a reason for it. A student who has trouble with math in high school may feel relief by avoiding math in college. Given a choice, the student might never take another math class, even if (in reality) the student would do well in a college math class. The student feels relief each time math is avoided. The avoidance behavior could last forever unless the student summons up the courage to take math and find out "it is really not so bad."


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