A Microanalysis of the Controlling Stimulus-Response Relations Engendered During the Assessment of Stimulus Overselectivity

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In this study, a microanalysis was conducted on the controlling stimulus-response relations engendered during the assessment of stimulus overselectivity in profoundly retarded adults when a two-choice discrete-trial discrimination procedure was used. Stimulus control by the elements of two-component stimulus complexes (S + and S - ) was assessed by presenting all possible juxtapositions of the individual elements on interspersed probe trials. After this assessment, the discrimination was reversed such that the prior S 4 + was the current S — and vice versa. Probe trials were again presented. The results indicated that those participants exhibiting overselective responding did so as a result of their behavior being controlled by a heterogeneous group of controlling stimulus-response relations. Those controlling relations included control by contextual factors, S — stimuli, and stimulus position. Reversing the discrimination resulted in a reversal of responding on most probes juxtaposing S + and S — elements. Responding on some probes did not reverse, thereby suggesting that historical factors may have influenced this performance. As a result of this historical intrusion, two participants, not overselective during the original discrimination, exhibited overselective responding during the reversal. Overall, the present study suggested that stimulus overselectivity may not be a homogeneous phenomenon resulting solely from restricted stimulus control or control by irrelevant stimuli, but instead may be a heterogeneous phenomenon involving complex patterns of stimulus control in which contextual and historical factors may play important roles.