AN ANALYSIS OF THE FACILITATIVE EFFECT OF SIMILARITY ON 2ND-ORDER CONDITIONING

Five experiments used autoshaping in pigeons to investigate the effect of stimulus similarity on 2nd-order conditioning of 1 stimulus (S2) when it signals another previously conditioned stimulus (S1). Experiment 1 found that the artificial induction of similarity between S2 and S1, by the addition of experimentally separable common elements, improved performance during 2nd-order conditioning of S2. Stimulus similarity encouraging the selection of particular compnents of S1 for association with S2 was discussed. Selection was described as a natural consequence of the temporal relations among components of S2 and S1 which their similarity ensures. Circumstances under which the normal facilitative effect of similarity could be reversed once observed (experiments 2A and 2B) or prevented from developing initially (experiments 3 and 4) were generated. A particular account of how a qualitative relation can affect the course of conditioning was given.