Slide 7

This general approach, that of seeing behavioral adaptation as one behavior coming to predominate over others can be formalized in a two alternative choice procedure. That is, how does one behavior come to predominate over another? This model of behavior has a quantitative specification of the probability of each behavior as a function of the available reinforcers.

A second important fact in behavioral adaptation is stimulus control, that is, the stimulus in whose presence a behavior is reinforced comes to control that behavior on its future occurrences. Stimuli in whose presence behavior is not reinforced fail to control or (suppress) that behavior on their future occurrences..

One example of stimulus control is temporal control. The temporal stimuli in effect at the moment of reinforcement would be expected to control responding. The temporal stimuli in effect when reinforcement does not occur would be expected to control nonresponding.

A simplistic prediction is, then, that a schedule with a temporal requirement such as one that reinforces the first peck following some fixed amount of time, should result in a single perfectly placed response.

When empirically evaluated, this schedule does not produce the expected result. Rather, it controls responding in the latter portions of the interval rather than controlling only a single response.

There are obvious candidates for why the simplistic prediction fails. Either reinforcement could strengthen more than just the last response, or the stimuli may be impossible to discriminate.

There is an empirical challenge to the indiscriminability hypothesis. If a short trial includes four stimuli, then responding occurs to only the last two stimuli. If the trial is lengthened, then responding occurs to all four stimuli. It is not plausible that the stimuli become harder to distinguish as the result of a longer trial.

Date Last Reviewed : August 19, 2002