Evolution of behavioural flexibility and the forming and breaking of habits

Abstract 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. Significance statement The forming and breaking of habits has long been a focus of study in psychology, as well as appearing in many discussions about human behavior. Surprisingly, the topic has been virtually absent from evolutionary studies of learning in non-human animals, despite featuring prominently in Darwin’s discussion of the evolution of species-specific behaviors. Our aim is to change this, by theoretically investigating a possible evolutionary explanation for habits, namely that habits enhance an individual’s ability to multitask. We model the combination of foraging and antipredator vigilance, which is important for many animal species in their natural environments. We conclude that the forming and breaking of habits can promote behavioral flexibility, helping animals to achieve important tasks in different environments. Competing Interest Statement The authors have declared no competing interest. Footnotes S.R.X.Dall{at}exeter.ac.uk p.hammerstein{at}biologie.hu-berlin.de A.I.Houston{at}bristol.ac.uk A.L.W.Kuijper{at}exeter.ac.uk john.mcnamara{at}bristol.ac.uk This version contains an updated model and updated analyses