Overt “mediating” behavior during temporally spaced responding

A rat was trained on a schedule that programmed reinforcements only when a minimum waiting time between successive responses was exceeded (DRL schedule). It was observed to fill much of the pause between lever presses with a stereotyped behavioral chain: it would take its tail in its mouth and nibble it. This behavior was shown to be functionally related to the efficiency with which the subject spaced its responses. It is thought to have served as mediating behavior, providing discriminating stimuli for appropriate lever presses.     

Combining Operant baseline derived Conditioned Excitors and Inhibitors from the Same and Different Incentive Classes: An Investigation of Appetitive-Aversive Interactions

The dynamics of appetitive-aversive interaction theory were assayed in an experiment where excitors and inhibitors from the same and different incentive classes were compounded. Excitatory and inhibitory incentive properties acquired by the discriminative stimuli resulted from the reinforcement differences between components of four-component multiple training schedules, with the influence of competing peripheral responses factored into the design. Rats' barpressing was maintained in tone and in click by food or free-operant shock avoidance; extinction was programmed in click-plus-light and in the simultaneous absence of tone, click, and light. In Test 1, an excitor that occasioned operant responding and an inhibitor that occasioned response cessation were compounded. Here, compounding an inhibitor with an excitor from the same incentive class reduced responding significantly more than did compounding an inhibitor with an excitor from the other incentive class. In Test 2, the compounds consisted of elements that individually occasioned operant responding. Here, compounding stimuli that were excitors from different incentive classes appeared to create reciprocal inhibition that counteracted the additive effects produced when these stimuli were excitors from the same incentive class. Predictions from appetitive-aversive interaction theory and Weiss' two-factor model of stimulus control were confirmed within this experimental design, where all conditioning was a by-product of the behavioural contingencies programmed on the operant baselines.