Your differential reinforcement CA: What to watch for

Revised on 3/29/14

Some of you have begun turning in your differential reinforcement CAs for Ch. 7. That reminds me that it's time to say something about the most common stumbling block for students doing this CA. And if you choose one of the other differential contingencies for extra credit, what I'm going to say here will apply to that one too.

In the differential contingencies, the two behaviors start out (that is, before the contingency is imposed) being members of the same response class. In simple terms, this means that they're similar to each other. Look at the diagram on p. 124. Hitting a tennis ball with some skill and hitting it without any skill are members of the response class that we could call "hitting a tennis ball." We could say that they're two subclasses of the larger response class. They're similar, though there's a key difference between them.

When a differential contingency is applied, members of one subclass are reinforced or punished (depending on the particular contingency) while members of the other subclass are not. As a result, the frequencies of the two subclasses diverge. The frequency of one subclass ends up being higher than the other. At this point we can say that the two subclasses have each become new response classes in their own right. In sum, the result of a differential contingency is to divide a response class into two different response classes.

But back to the point I started with. In an example of a differential contingency, the two behaviors have to be similar to each other in at least one of the ways that Malott says members of a response class are similar to each other (p. 128). So when you're preparing your differential reinforcement CA, be sure the two behaviors are similar.

Doing that will also help you avoid another common mistake made by students on the differential contingencies – describing a non-behavior in one of the behavior boxes. If you're reinforcing the behavior described in the upper behavior box, and not reinforcing (extinguishing) the "not doing" of that behavior as described in the lower behavior box, then that's no different from simple reinforcement, in which you reinforce the behavior described in the upper behavior box. Make sure what's described in both behavior boxes is something a dead man can't do.