Effects of conditional discrimination training on object identification: Implications for selective stimulus control

In the present research, the degree of stimulus control exerted by each of the two dimensions (color and shape) of compound stimuli was studied in two experiments with undergraduate college students. A between-groups design with three consecutive experimental phases was used in each experiment. Phases 1 and 2 were training phases; Phase 1 consisted of single stimulus discrimination training and Phase 2 consisted of compound stimulus discrimination training. Phase 3 was testing in which stimuli were presented to assess the degree to which responding corresponded to the Phase 2 training. In Experiment 1, congruence of reinforcement contingencies between training phases was manipulated for a target dimension in a graded manner---100%, 25%, or 0%. There was a systematic decrease in the level of Phase-2-consistent responding in the presence of the target dimension corresponding to the decreases in the level of congruence present during Phase 2. In Experiment 2, training history for the non-target dimension was altered in order to influence the extent to which the non-target dimension exerts stimulus control. The three experimental conditions under which the Phase 1 training history for the non-target dimension was manipulated were: (a) Correlated with reinforcement, as in Experiment 1, (b) Absent, or (c) Not Correlated consistently with reinforcement. Under the Absent condition, the non-target dimension was not presented in Phase 1. Under the Not Correlated condition, inconsistent prior training for the non-target dimension was presented. The identical manipulation of the congruence of the reinforcement contingencies for the target dimension used in Experiment 1 was used in Experiment 2. There was an effect of the manipulation of the prior training history for the non-target dimension on the level of Phase-2-consistent responding in the presence of the target dimension. Correlated prior training compared to Absent and Not Correlated prior training for the non-target dimension led to greater competition, indicated by high Phase-2-consistent responding in the presence of the non-target dimension and reduced target performance.