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Differential Reinforcement

Differential reinforcement is selective reinforcement of one behavior from among others. Unlike shaping, differential reinforcement is used when a behavior already occurs and has good form (does not need shaping) but tends to get lost among other behaviors. The solution is to single out the desired behavior and reinforce it.

What is differential reinforcement? How is it distinguished from shaping? What is a "response class"?

Differential reinforcement is commonly applied to a group of behaviors. For example, if one was working in a day care center for children, one might reinforce any sort of cooperative play, while discouraging any fighting. The "cooperative play" behaviors would form a group singled out for reinforcement. Such a group is labeled a response class. A response class is a set of behaviors—a category of operants—singled out for reinforcement while other behaviors are ignored or (if necessary) punished. The only limitation on the response class is that the organism being reinforced must be able to discriminate it. In the case of preschoolers at a day care center, the concept of cooperative play could be explained to them in simple terms. Children observed to engage in cooperative play would then be reinforced in some way that worked, for example, given praise or a star on a chart or more time to do what they wanted.

How did Pryor reinforce creative behavior?

Karen Pryor is a porpoise trainer who became famous when she discovered that porpoises could discriminate the response class of novel behavior. Pryor reinforced two porpoises at the Sea Life Park in Hawaii any time the animals did something new. The response class, in this case, was any behavior the animal had never before performed. Pryor set up a contingency whereby the porpoise got fish only for performing novel (new) behaviors. At first this amounted to an extinction period. The animals were getting no fish.

How did the porpoises' natural reaction to extinction help Pryor?

As usual when an extinction period begins, the porpoises showed extinction-induced resurgence. In other words, the variety of behavior increased, and the porpoises showed a higher level of activity than normal. They tried their old tricks but got no fish. Then they tried variations of old tricks. These were reinforced if the porpoise had never done them before. The porpoises caught on to the fact that they were being encouraged to do new and different things. One porpoise "jumped from the water, skidded across 6 ft of wet pavement, and tapped the trainer on the ankle with its rostrum or snout, a truly bizarre act for an entirely aquatic animal" (Pryor, Haag, & O'Reilly, 1969). The animals also emitted four new behaviors—the corkscrew, back flip, tailwave, and inverted leap—never before performed spontaneously by porpoises.

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