Abstract
Previous studies have demonstrated that the thirst drive interferes with the hunger drive in an animal's performance of motivated behavior: water deprivation causes a reduction in food-reinforced instrumental performance of food-deprived rats. In other words, irrelevant thirst causes devaluation of the food reinforcer. Here, we examined whether this type of reinforcer devaluation effect would require the animal's consummatory contact with the reinforcer under the irrelevant drive (i.e., incentive learning). Three groups of food-deprived rats were trained to press a lever for food pellets. Next, two groups (HT-pel and HT-) were cumulatively deprived of water, whereas the other group was deprived of food alone (H-pel), and all animals received an extinction test on the lever. Thereafter, groups HT-pel and H-pel were allowed to consume pellets, and lever pressing was tested again in extinction for all animals. We found that the irrelevant thirst, by itself, did not affect instrumental performance. However, the animals exposed to pellets under irrelevant thirst (HT-pel) exhibited a reduction in instrumental performance, suggesting incentive learning's role in the reinforcer devaluation effect caused by the irrelevant drive state.
