Incentive salience attribution is not the sole determinant of suboptimal choice in rats: Conditioned inhibition matters

摘要

Highlights ? We studied rats preference for discriminative vs non-discriminative alternatives. ? Suboptimal behavior has been linked to the incentive salience of the discriminative stimuli. ? The only study demonstrating suboptimal choice in rats lacked a conditioned inhibitor. ? Our procedure involved both a conditioned inhibitor, and discriminative stimuli with incentive salience. ? Rats were optimal, suggesting that the conditioned inhibitor plays a crucial role in rats choice. Abstract Previous research has identified clear differences between pigeons and rats in the suboptimal choice procedure. Pigeons behave suboptimally, preferring an alternative with discriminative stimuli and a smaller probability of reinforcement, over another with a higher probability of reinforcement, but without discriminative stimuli. In contrast, rats behave optimally showing the opposite preference. It has been proposed that these dissimilarities are consequence of a higher sensitivity to conditioned inhibition in rats than in pigeons. Alternatively, recent research suggests that differences in optimality can be accounted for by a differential incentive salience of the stimuli employed as discriminative stimuli, and that both species are suboptimal when such stimuli have high incentive salience; specifically, rats were found to be suboptimal when levers were used as discriminative stimuli. However, in the evaluation of this hypothesis, a conditioned inhibitor was not employed. In the present report, eight rats were exposed to a choice procedure that integrated both variables discussed above: a conditioned inhibitor was associated with the discriminative alternative and the stimuli had high incentive salience. A clear preference for the optimal alternative was found, suggesting that the conditioned inhibitor had a considerable impact on rats’ preference, and that species-differences remain even in procedures in which the discriminative stimuli have incentive salience. ]]>