Control by exclusion in arbitrary matching-to-sample

Eight handicapped youths were taught arbitrary matching between visual sample stimuli and visual comparison stimuli: Given Sample A1, selecting Comparison B1 was reinforced; given A2, selecting B2 was reinforced. During nonreinforced test trials consisting of novel samples, novel comparisons, and familiar B comparisons, subjects selected the novel comparisons. Compared to intervening preference tests between novel comparisons, these results suggested that selecting the novel stimuli was controlled by the B comparisons, a phenomenon called exclusion. Some subjects continued to select the same novel comparisons during subsequent preference tests, suggesting that control by exclusion may result in arbitrary matching in new contexts. emonstrated symmetry of AB matching (i.e., BA matching) suggested that A stimuli should also control novel comparison selection; however, these subjects did not show exclusion, but most often selected the A comparisons.