TEMPORAL LOCATION OF UNSIGNALED FOOD DELIVERIES - EFFECTS ON CONDITIONED WITHDRAWAL (INHIBITION) IN PIGEON SIGNTRACKING

Standard models of Pavlovian conditioning neglect local effects of uns ignaled unconditioned stimuli (USs) on learning and performance. Using the approach-withdrawal behavior of pigeons toward keylights as condi tioned stimuli (CSs), the authors varied the specific times (5-110 s) that USs occurred before or after a CS. Withdrawal from a CS generally increased as the time between a US before and/or after the CS was len gthened. Combinations of 2 distant USs produced more withdrawal from t he CS than either US alone, whereas combinations of a distant and a ne arby US yielded behavior intermediate between that for either US alone . Postacquisition retardation tests supported similar conclusions. Bas ed on the temporal isolation of CSs and USs, a tentative model was off ered to summarize these data. The results and the model suggest that a more molecular, possibly perceptual approach to Pavlovian excitation and inhibition is needed.