Responding by exclusion in temporal discrimination tasks

Abstract

Responding by exclusion, one of the most robust phenomena in Experimental Psychology, consists of choosing an undefined comparison stimulus given an undefined sample, when the comparison stimulus is presented next to other experimentally defined stimuli. The goal of the present study was to determine whether responding by exclusion could be obtained using samples that varied along a single dimension. Using a double temporal bisection task, ten university students learned to choose visual comparisons (colored circles) based on the duration of a tone. In tests of exclusion, sample stimuli with new durations were followed by comparison sets that included one previously trained, defined comparison (colored circle) and one previously untrained, undefined comparison (geometric shape). Subjects preferred the defined comparisons following the defined samples and the undefined comparisons following the undefined samples, the choice pattern typical of responding by exclusion. The use of samples varying along a single dimension allows us to study the interaction between stimulus generalization gradients and exclusion in the control of conditional responding.