Date of Award:

1971

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Psychology

Advisor/Chair:

J. Grayson Osborne

Abstract

The present study was conducted as a systematic replication of earlier work investigating the phenomenon of behavioral contrast. Behavioral contrast has been consistently reported in alternating two component multiple schedules using infra-human subjects. The present study was interested in answering the question, "Does behavioral contrast exist in humans?"

Two experiments were performed which investigated the behavioral contrast and sequential contrast phenomena in children. In both experiments, lever press responses were analyzed using an ABA single-subject design. The children were instructed to press a lever to obtain as many tokens as possible. In Experiment I, six Ss were equally divided into two groups of three subjects each. Group I, the mult VI EXT group began the experiment by responding on an alternating two component multiple variable interval (VI) 20 seconds, extinction (EXT), mult VI EXT, schedule of reinforcement. Following stabilization of response rates on a mult VI EXT schedule, Phase I, the three Ss in this group progressed through Phase II, a mult VI 20 second schedule of reinforcement, and Phase III, a mult VI 20 second EXT schedule of reinforcement. Group II, the mult VI VI group began the experiment by responding on a mult VI 20 second VI 20 second schedule of reinforcement. Following stabilization of response rate on the mult VI VI schedule, Phase I, the three Ss in this group progressed through Phase II, the mult VI 20-sec EXT schedule of reinforcement, and Phase III, a mult VI 20 second VI 20 second schedule of reinforcement.

Behavioral contrast, in an alternating two component multiple schedule, defined as an increase in response rate in one component accompanying a decrease in response rate in the alternate component was observed in Experiment I. Regardless of the sequence of exposure to the multiple schedule, all Ss showed similar response patterns under the same multiple schedules. For example, an increase in response rate in the unchanged VI component was observed in all Ss when the response rate in the alternating EXT (previously VI) component decreased (positive behavioral contrast). A decrease in response rate in the unchanged VI component was also observed in all Ss when an increase in response rate in the alternating VI (previously EXT) component occurred (negative behavioral contrast).

The appropriate change in response rate in the second component of a multiple schedule appeared to be prerequisite for the occurrence of behavioral contrast whether it be a decrease in responding when the second component programmed EXT or a stable response rate when the second component programmed a VI 20 second reinforcement schedule.

In Experiment II, three Ss were exposed to a mult VI 20 second EXT schedule of reinforcement the components of which were presented in a random sequence. Sequential contrast, defined as a greater response rate during S+ when an S+ is preceded by an S- component than when S+ is preceded by other S+ components was not consistently observed in the present experiment. One of three subjects exposed to the sequential contrast experiment showed a consistently higher rate of responding during S+ components that followed an S- component than when an S+ component followed another S+ component, but the other two Ss in the experiment failed to emit response patterns characteristic of sequential contrast.

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