Evolution of behavioral flexibility and the forming and breaking of habits.

The formation of habits, whereby learnt actions come to be performed automatically with repetition and practice, is a well-established focus for studies in psychology. This contrasts with evolutionarily motivated studies of learning, which typically view behavior as either learnt or fixed, to elucidate the ecological conditions where each predominates. Here, we envisage habit formation functioning to free up limited mental resources (e.g., attention), potentially improving an individual's ability to multitask. As an ecologically relevant case, we investigate exploration-exploitation in foraging under predation risk. In our model, a forager does not know the quality of feeding options, but can learn from the rewards they give. When the environment occasionally changes, individuals can attend to exploration of feeding options in the new conditions. The options can then become habitually exploited, freeing attention for antipredatory vigilance. Via evolutionary simulations, we show that evolutionarily stable forming and breaking of foraging habits can substantially reduce mortality from predation, without drastically reducing foraging success, when environmental conditions remain stable enough between changes. We identify factors promoting habit formation, such as the repetition of actions that yield predictable rewards, and also discuss the role of habits more generally, including their relation to ideas about bounded rationality in theories of decision-making. In conclusion, we argue that exploration-exploitation strategies involving the forming and breaking of habits are a type of behavioral flexibility that is likely to be selected for under a range of ecological conditions.