Theory of Mind

The ability of an individual to impute (attribute, assign) mental states to himself and to others (either to conspecifics or to other species as well). A system of inferences of this kind is properly viewed as a theory because such states are not directly observable, and the system can be used to make predictions about the behaviours or others. An individual may infer, for example, purpose or intention, as well as knowledge, belief, thinking, doubt, guessing, pretending, liking and so forth. See also empathy and sympathy.

Theory of Mind is the ability to understand that other people have their own thoughts, feelings, and intentions that are different from your own. Because people cannot directly see inside someone else's head, they form a "theory" about what they are thinking or feeling to predict what they will do next.

Reference:

Premack, D., & Woodruff, G. (1978). Does the chimpanzee have a theory of mind?. Behavioral and Brain Sciences, 1(04), 515-526. https://doi.org/10.1017/S0140525X00076512