Choice Between Reinforcers With and Without Delayed Shock Effects of a Pre-Shock Signal

Choice research has largely emphasized situations in which individuals choose between a smaller-sooner reward and a larger-later reward. However, in many situations, choosing a certain one of the options results in conflicting consequences: an immediate reinforcer and a delayed punisher. Recent research with rats has evaluated how choice between a smaller reinforcer alone and a larger reinforcer with a delayed shock changes as a function of shock intensity and delay. Research in this area has also evaluated the effects of signals that follow the response and precede shock with conflicting results. The present experiment investigated a different signaling procedure, one that only precedes shock, in a choice procedure. Rats chose between one food pellet and two pellets with a delayed shock. Shock intensity and signal presence were manipulated across conditions. Using an adjusting delay procedure, the delay to shock was adjusted based on the rats’ choices. Choice for one food pellet raised the delay to shock in subsequent trials and choice for two pellets with shock reduced the delay in subsequent trials. Adjustments continued within each condition until the rat chose both options equally (indifference) or until choice for the two pellets with shock persisted. In general, higher shock intensities devalued the two pellets to the greatest extent, resulting in longer adjusting delays before indifference was reached. The signal, however, had no consistent effect on choice. Procedural differences across experiments evaluating signaled shock are discussed as possible explanations for conflicting findings regarding the effect of the signaled shock on behavior