Theory of mind (ToM) is a term used to describe a person’s ability to understand another person’s mental states. It overlaps with, but is not the same as, empathy for another person. The most common test of ToM is the false belief task that determines whether a person can understand that another person holds a false belief. Children can usually pass this test by the time they are about 4 years old, although many autistic children can never pass the false belief test. The development of ToM usually improves as a child grows older, parallel to language development. It has been argued that the mirror neuron system is involved with both the development of ToM and language learning. There are several theories of ToM and growing development of computer models of ToM, as they are useful to the development of artificial intelligence. For sociologists, ToM is an important cognitive development that underlies many of the social processes that are the topic of sociological study.