STIMULUS COMPARISON AND PERCEPTUAL-LEARNING - FURTHER EVIDENCE AND EVALUATION FROM AN IMPRINTING PROCEDURE

Two experiments used chicks to investigate the role of stimulus compar ison in perceptual learning. In Experiment 1, chicks received exposure to two views of a jungle fowl, SV (side view) and BV (back view), int ermixed within a session (mixed exposure), exposure to SV in one sessi on and BV in a different session (separate exposure), or no exposure t o either view All chicks then received a heat-reinforced discriminatio n with SV and BV serving as discriminanda. Chicks given mixed exposure acquired the discrimination more readily than did either those given separate exposure or those given no exposure. In Experiment 2, all chi cks received mixed exposure to the two stimuli. For one group the inte rval between presentations of the stimuli was short (short-mixed), for the other group it was long (long-mixed). Subjects in the long-mixed condition acquired the heat-reinforced discrimination more rapidly tha n those in the short-mixed condition. These results suggest that the i ntermixed nature of stimulus exposure is an important determinant of t he magnitude of perceptual learning effects.