Why do animals make better choices in patch-leaving problems?

This study compares two procedures for the study of choices that differ in time and amount, namely the self-control and patch procedures. The self-control procedure offers animals a binary mutually exclusive choice between a smaller-sooner and larger-later option. This procedure dominates the choice literature. It seems to address the idea of choice in a general, but relatively abstract way. Animals in the self-control situation frequently prefer the smaller-sooner option even when the larger-later option yields a higher long-term intake rate. In contrast, the patch procedure poses an economically similar question, but simulates the naturally occurring problem of patch exploitation. In the patch procedure, animals choose between leaving and staying. Emerging evidence suggests that animals perform better and achieve higher long-term intake rates in the patch situation. This observation raises the question of how a single set of choice mechanisms could produce these different outcomes. The experiment presented here tests two hypotheses about the relationship between the patch and self-control situations. First, it asks whether the short-term rate rule can predict choice behavior in both situations. Second, it tests the second-delivery hypothesis which holds that the patch situation favors choosing the larger more delayed option (staying) because this option ultimately leads to two food deliveries. The results of this experiment convincingly reject both of these hypotheses. Indeed, our results suggest that none of the simple rules based on time and amount can explain the observed differences between the patch and self-control situations. This result challenges the generality of existing models of choice. (C) 2008 Elsevier B.V. All rights reserved.