Theory of mind is the recognition that others have mental states, just as you do. It is the ability to put yourself in someone else’s shoes, to acknowledge that their mental state—their beliefs, their perspectives, how their experiences have shaped them—differs from your own. And therefore that, when people act a certain way, they are responding not to an objective reality but to their own particular perceptions of that reality, which are likely not the same as yours.

False-belief understanding lies at the crux of this concept. It involves understanding when another person has a mistaken belief, and a prerequisite for that understanding is figuring out what the other person believes. And now there’s some evidence that we’re not the only species with it.

Theory of mind

Humans possess this theory of mind, along with its all-important false-belief understanding. But it is still an open question whether humans alone possess it. Our closest relatives, the great apes—bonobos, chimpanzees, and orangutans—have exhibited theory of mind in some experiments.