Within-session Change Research Articles

Within-session patterns of responding when rats run in a T-maze

Free-operant responding changes systematically within experimental sessions, usually increasing and then decreasing, even when the contingencies of reinforcement remain constant within the session. The present study extended this finding to running times in a T-maze. In Experiment 1, running times changed significantly within the session. Furthermore, the within-session pattern of running times changed with changes in the amount or rate of reinforcement. In Experiment 2, the within-session change in running times was found to be independent of the accuracy of responding. In Experiment 3, manipulating whether responding and/or reinforcement occurred early in the session did not affect the pattern of running times later in the session. The present results increase the generality of within-session changes in responding to a discrete-trials procedure. Furthermore, within-session patterns of running times usually changed in a similar manner as within-session patterns of free-operant responding when similar factors were manipulated. Thus, the same factors may be producing the changes in both situations.

WARMUP IN FREE‐OPERANT AVOIDANCE AS A FUNCTION OF THE RESPONSE‐SHOCK = SHOCK‐SHOCK INTERVAL

Warmup effects, the repeated within-session transitions from ineffective to effective avoidance, were examined with rats on free-operant shock-delay procedures. The shock-shock and response-shock intervals were kept equal as they were varied. As measured by both response rates and shock rates, the magnitude of within-session change in performance was inversely related to the size of the manipulated intervals. The duration of warmup tended to decrease as the intervals were increased. This finding, that increased shock frequencies do not shorten the warmup, appears to be inconsistent with all interpretations of the warmup that have been offered to date. Late-session performances replicated general features of prior experiments, but differed with respect to details of secondary conclusions in previous reports. These differences may stem from the selection of especially proficient avoiders for previous experiments.