Theory of mind
The capacity to attribute mental states — beliefs, desires, intentions — to others and to oneself.
What it means
Theory of mind is the capacity to represent and reason about mental states — beliefs, desires, intentions, knowledge, and emotions — and to recognize that others hold states that may differ from one's own and from reality. It is the cognitive foundation of human social life, underpinning communication, cooperation, teaching, persuasion, and deception, all of which require modeling what is in another mind. The classic test is the false-belief task, which a child typically passes around age four when they grasp that a person will act on a mistaken belief about the world rather than on the true state of affairs. Its mechanisms are debated between 'theory-theory' (we deploy an intuitive theory to infer others' states) and 'simulation theory' (we imaginatively put ourselves in their shoes), and it is supported by a distributed brain network. The limits of theory of mind generate failures such as the curse of knowledge, where one's own knowledge contaminates judgments of what others know. It matters because almost every coordinated human activity depends on accurately inferring other people's minds, and deficits in it (as in some clinical conditions) profoundly disrupt social functioning.
Examples
A child passes a false-belief test when they grasp that someone will look for an object where they last saw it, not where it has secretly been moved.
A good teacher pitches an explanation to what the student does not yet know, constantly modelling the gap between their own understanding and the mind in front of them.
Bluffing at poker only works if you can model what your opponent believes about your hand — you are betting on a picture inside someone else's head.
First described in Premack & Woodruff (1978).