Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Special Education and Rehabilitation


Timothy A. Slocum


Behavioral contrast occurs when a change in reinforcement rate in one context causes behavior to change in the opposite direction in another context. Positive contrast occurs when a decrease in the rate of reinforcement in one context results in an increase in behavior in another context. Negative contrast occurs when an increase in the rate of reinforcement in one context results in a decrease in behavior in another context. Research with nonhumans has found that positive contrast is more reliably produced than negative contrast. Research with nonhumans has also found that positive contrast is influenced to a larger degree by changes in reinforcement rate in the following context (vs. in the preceding context); however, results regarding negative contrast and the influence of preceding versus following contexts have been mixed. Finally, within-session contrast effects have been demonstrated in nonhumans. Relative to the entire environmental context, the largest change in behavior occurs immediately prior to (anticipatory contrast) or immediately following (local contrast) the change in reinforcement rate. Behavioral contrast has applied implications, in that practitioners may only be able to implement interventions in one context, which may result in concomitant worsening of behavior in other contexts. Few studies with humans have compared positive and negative contrast, and none have separated preceding- and following schedule effects or have systematically investigated within-session contrast. The purpose of this study was to investigate these effects in humans in a translational arrangement. Positive contrast was found in five of six cases, while negative contrast was found in only three of six. The effect of the following schedule was larger with positive contrast, but the effect of the preceding schedule was larger with negative contrast. There were no systematic within-session effects characteristic of anticipatory or local effects.