Investigating retrospective influences on induction in rats' responding for 1% sucrose when food-pellet reinforcement is upcoming.

Abstract

When rats lever press for 1% sucrose reinforcement in the first half of a 50-min session, response rates are higher when food-pellet reinforcement will be available in the second half than when 1% sucrose will be available. Results of past research have suggested that, under some conditions, this induction effect is prospective in nature (i.e., controlled by the conditions of reinforcement in the present session). However, that research did not rule out the possibility that, under other conditions, retrospective factors (i.e., the conditions of reinforcement in the previous session[s]) could contribute. In the present study, rats responded in two types of session, one in which 1% sucrose reinforcement was available in both halves of the session and one in which 1% sucrose and food-pellet reinforcement were available in the first and second halves, respectively. Which type of session was in effect unsignaled and session type alternated every session (Experiment 1), every second session (Experiment 2), or after at least 20 consecutive sessions of one type (Experiment 3). Across experiments, the results indicated that it takes several sessions of one type for observable retrospective effects to occur, but those effects are short lived. These results allow the authors to identify the mechanisms that must underlie induction. The authors also discuss induction as an animal model of anticipation.