Three Different Ways that Reinforcers Affect Behavior
When presenting some event or activity dependent on a response makes that response more likely in the future, we say that reinforcement of the response has occurred. This sometimes is described as the strengthening effect of a reinforcer. It is by far the most well- known reinforcer effect. There are, however, at least two other effects of reinforcers on responding that are less talked about, but important nonetheless.
A positive discriminative stimulus, or “ess-dee” (for S-D) as it sometimes is called, is one in the presence of which a response is reinforced. A negative discriminative stimulus, or “ess delta” is one in the presence of which the response is not reinforced. Because the reinforcer always occurs after a response, the reinforcer can come to serve as a stimulus. As a stimulus, it can signal whether the next response is likely to be reinforced or not. If every response is reinforced, then the reinforcer signals that the next response is likely to be reinforced. If reinforcement occurs only occasionally, then a reinforcer delivered signals that is not likely that the next response will be reinforced. In either case, at the same time the reinforcer is strengthening the responses that it follows, it also is guiding behavior that follows the reinforcer. When reinforcement is intermittent (occasional), the discriminative function of a reinforcer can be complicated: it can signal that reinforcement of a response is unlikely for a while, but thereafter may become more and more likely. For example, in a fixed-ratio 10 schedule, where reinforcers are delivered after every 10 responses, the reinforcer signals both that the next nine responses will not be reinforced, but also that after 10 more responses, a reinforcer will be forthcoming. This in the context of a history of reinforcement according to the fixed-ratio 10 schedule yields a pattern of pausing (not responding) immediately after a reinforcer, followed by a high rate of responding to the next reinforcer.
Reinforcers also can serve a third function: that of what is called inducing responding. When there is a period of nonreinforcement after a reinforcer delivery, there is strong possibility that behavior other than reinforced response will occur. What that other behavior is depends on what other kinds of things are present in the environment. If, for example, a rat’s lever pressing is reinforced, during the period after a reinforcer and before the operant response resumes, the rat will run in a running wheel if one is available or it will drink copious amounts of water if water is available. This type of behavior in the post-reinforcement period is labeled schedule-induced behavior, and it is determined by the type of reinforcer, the schedule of reinforcement, and the kinds of objects that are available in the environment. There is, for example, research that suggests that alcohol or drug consumption sometimes can be considered examples of schedule-induced behavior.
These three different functions of the reinforcer – strengthening, discriminative stimulus, and response inducing - suggest the complexities of using reinforcers to change behavior. Sometimes, for example, when reinforcers have unexpected effects on behavior, it may not be because there is something “wrong’ with the reinforcer, but simply because we are not considering the multiple ways in which reinforcers might affect behavior.