Asymmetrical interactions between thirst and hunger in Pavlovian-instrumental transfer.

Pavlovian-instrumental transfer experiments have demonstrated that a stimulus paired with a sucrose solution under hunger will increase instrumental performance under thirst relative to a stimulus previously paired with food pellets. In Experiment 1 it was demonstrated that this difference is, in part, produced by suppression induced by the pellet stimulus, which, it was found, acted to reduce instrumental performance under thirst. In Experiment 2, the reverse shift was examined, comparing the effects of stimuli paired with either a saline solution or a sucrose solution under thirst on instrumental performance under hunger. Although the sucrose stimulus was found to elevate performance when hungry, the saline stimulus was found to be without effect. This asymmetry in the interaction between hunger and thirst is discussed in terms of the way motivational states control the interaction between sensory and affective components of the reinforcer.