Decision-making biases in animals: A critical review

Humans make thousands of decisions every day, and in some situations, we make reliably bad ones. Much research has explored the circumstances in which such irrational decision-making occurs, but the underlying mechanisms are often unclear. One approach that has recently gained traction is to study other species’ responses to similar scenarios to better understand our own decision-making strategies. Here we provide a critical discussion of experimental studies of decision-making biases in animals. We begin by demonstrating how comparative research can yield unique insights into our own decision-making that cannot be gained from studying humans alone. In particular, while comparative research helps us better understand how and why decision-making biases have evolved and which mechanisms underlie them, such studies often overlook how these behaviors vary, both within and between individuals. Methodological concerns and a lack in the diversity of species studied and the number of animals tested complicate this issue and can limit the inferences we can draw. We emphasize the need to study why and when some animals would be expected to show these biases while others would not. Further, rather than just assess whether a given bias is present, comparative research should measure the extent to which it is. We argue that studying how susceptibility to biases varies both within and between individuals is crucial to better understanding the nature of irrational decision-making. We suggest practical steps that open up exciting avenues for future comparative research in this area.