Contributions of delay, duration, and intensity of shock on rats' choices involving conflicting-valence consequences.

Abstract

Problems related to "self-control" can occur in situations in which a single choice produces both reinforcing and aversive consequences. We exposed rats to choice situations in which a press on one lever produced only food and a press on a second lever produced food and delayed shock. Within and across conditions of four experiments, adjusting-delay procedures were used to identify indifference points-delays at which the consequences produced by the two levers exerted equal control over choice. Experiment 1 investigated the effects of intensity and duration of delayed shock on choice between a small food reinforcer or a large food reinforcer followed by delayed shock. Experiment 3 investigated the effects of shock's delay on choice between food delivered immediately and followed by delayed shock or food delivered after a delay. Experiments 2 and 4 investigated the effects of signaling the delayed shock in Experiments 1 and 3, respectively. The effects of delayed shock on choice were a direct function of shock intensity and shock duration and an inverse function of shock's delay. Signals did not affect choice systematically. The results extend findings from research on the punishment of operant behavior and on the temporal discounting of reinforcing and punishing events.