Doctor of Philosophy (PhD)



Document Type



Two experiments were conducted in an attempt to occasion both positive and negative contrast effects. The primary purpose was to occasion both decrements and increases in responding following planned shifts in quality or magnitude of reinforcement. Participants were children ages 7 to 16 years who were receiving therapy using Applied Behavior Analysis (ABA) and had a prior diagnosis of autism. In Experiment I, changes in responding were measured following manipulations of reinforcer quality. Results indicated response patterns consistent with negative contrast effects following shifts from high quality to low quality reinforcers, and positive contrast effects following shifts from low quality to high quality reinforcers. That is, responding in sessions following shifts from high to low magnitude reinforcers was lower than rates of responding in previous low quality conditions. Positive contrast was less consistently observed, but was seen as responding at higher rates during a second high-quality condition relative to the first following exposure to a low-quality condition. In Experiment II, responding was measured following shifts in reinforcer magnitude using a similar sequence of schedules as Experiment I. Both positive and negative contrast effects were observed, although less consistently than in Experiment I. Overall, the findings were consistent with the phenomena of positive and negative contrast effects in that one schedule of reinforcement produced changes in responding for a different schedule of reinforcement. Results were discussed in relation to the ideas of behavioral contrast and studies of intrinsic motivation.



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Committee Chair

Noell, George

Included in

Psychology Commons