REMINISCENCE AND FORGETTING IN A RUNWAY

Responding changes systematically within sessions during conditioning procedures

When the procedure is held constant within an experimental session, responding often changes systematically within that session. Many of these within-session changes in responding cannot be dismissed as learning curves or by-products of satiation. They have been observed in studies of positive reinforcement, avoidance, punishment, extinction, discrimination, delayed matching to sample, concept formation, maze and alley running, and laboratory analogues of foraging, as well as in the unconditioned substrates of conditioned behavior. When aversive stimuli are used, responding usually increases early in the session. When positive reinforcers are used, responding changes in a variety of ways, including increasing, decreasing, and bitonic functions. Both strong and minimal reinforcement procedures produce within-session decreases in positively reinforced behavior. Within-session changes in responding have substantial theoretical and methodological implications for research in conditioning.

Trial Spacing in Instrumental Running

Trial spacing was studied over 120 acquisition trials and 20 each of extinction, reacquisition, and re-extinction, using five intertrial intervals from 40 sec. to 120 min. in between four daily trials. Throughout acquisition, performance of the 120-min. group increased throughout the course of a daily block, while the others first increased, then decreased. Spontaneous regression persisted throughout acquisition. Extinction performance was not systematically related to trial spacing, and no evidence for spontaneous recovery was found. Changes in measured spatial variability in the alley indexed learning but did not differentiate trial spacing effects. The results generally failed to confirm qualitative hypotheses about trial spacing derived from statistical learning theory.