Behavioral Contrast and Alternative Response Key Availability
Townsend, Kari Lebeda
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The Problem. This study investigated the interaction of schedules of reinforcement on behavior, replicating and extending Keller's (1 974) research. Expanded methodology included two control manipulations designed to clarify Keller's previously ambiguous findings. The influence of stimulus properties and the location of discriminative stimuli on the production of behavioral contrast was examined. Procedure. Pigeons in Group 1 were exposed to a two-key procedure in which one key served as the operandum and the other key signaled scheduled consequences (see Keller,1974). The pigeons in Group 2 were exposed to the same two-key procedure; however, the positions of the keys alternated locations. In Group 3, pigeons were exposed to a two-key procedure in which the key that signaled scheduled consequences was the operandurn and the other key was irrelevant with no signal properties or scheduled consequences. All subjects were exposed to a baseline of a multiple variable-interval 1- minute variable-interval 1-minute schedule (mult VI 1-min VI 1-min), an experimental phase of a multiple variable-interval 1-minute extinction (mult VI 1-min EXT) and a return to baseline phase. Findings. Overall, pigeons in Group 1 and Group 2 exhibited negative induction while pigeons in Group 3 exhibited positive behavioral contrast. Pigeons in Group 2 also showed marked responding to the green key which signaled variable-interval 1-minute schedule of reinforcement in the experimental phase. which persisted in the reversal phase. Pigeons in Group 1 showed virtually no signal key pecking. In Group 3, pigeons showed no alternative key pecking. Conclusions. The results support Hearst and Gormley's (1 976) findings that positive behavioral contrast occurs only when discriminative stimuli signaling scheduled consequences are located on the operandum. These findings are also incompatible with additivity theory and Keller's (1974) findings. The results suggest that attentional factors and stimuli salience may serve as crucial variables in the production of the positive behavioral contrast phenomenon. Recommendations. Subsequent research should attempt to determine whether responses by pigeons in Group 2 to the green signal key associated with reinforcement were the byproduct of generalization or constituted adventitious reinforcement. Future research efforts should also show empirical evidence of discrimination and stimulus control.
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