FOOD DELIVERY AS A CONDITIONAL STIMULUS - FEATURE-LEARNING AND MEMORY IN PIGEONS

Three experiments investigated the learning and memory of discriminations based on presence versus absence of a pre‐trial food delivery. In Experiment 1 half the illuminations of a response key were followed by food regardless of the subject's behavior. In one group an extra food delivery preceded only reinforced trials (feature‐positive condition), whereas in a second group it preceded only nonreinforced trials (feature‐negative condition). Key pecks and approaches revealed more rapid and superior discrimination learning in the first group. Experiment 2 replicated the results of Experiment 1 but yielded no evidence that greater “unexpectedness” of pretrial food conditions facilitates discriminative performance. In Experiment 3, individual pigeons trained on a conditional discrimination exhibited a within‐subject feature‐positive superiority. Delay between pretrial and trial stimuli interacted with feature‐positive versus feature‐negative training in both the between‐group (Experiment 2) and within‐subject (Experiment 3) procedures: performance was decremented at both short and long delays in the feature‐positive condition but was decremented only at longer delays in the feature‐negative condition. The feature‐positive superiority obtained here is incompatible with explanations based on either the general concept of “perceptual organization” or on the conditional nature of feature‐negative discriminations. 1979 Society for the Experimental Analysis of Behavior