Laurie Santos runs the Comparative Cognition Laboratory (CapLab) at Yale, where she and collaborators across departments (from psychology to primatology to neurobiology) explore the evolutionary origins of the human mind by studying lemurs, capuchin monkeys and other primates. The twist: Santos looks not only for positive humanlike traits, like tool-using and altruism, but irrational ones, like biased decisionmaking.

In elegant, carefully constructed experiments, Santos and CapLab have studied how primates understand and categorize objects in the physical world -- for instance, that monkeys understand an object is still whole even when part of it is obscured. Going deeper, their experiments also search for clues that primates possess a theory of mind -- an ability to think about what other people think.

Most recently, the lab has been looking at behaviors that were once the province mainly of novelists: jealousy, frustration, judgment of others' intentions, poor economic choices. In one experiment, Santos and her team taught monkeys to use a form of money, tradeable for food. When certain foods became cheaper, monkeys would, like humans, overbuy. As we humans search for clues to our own irrational behaviors, Santos' research suggests that the source of our genius for bad decisions might be our monkey brains.