Theory of Mind refers to the capacity to attribute mental states to oneself and others in an attempt to understand and explain, and to predict other's behavior. ToM is not fully developed in children or adults with Autism.

Awareness and understanding of mental states and processes. (201)

A theory held by a child or adult about the way one's own mind and other people's minds work, and how people are affected by their beliefs and feelings. One hypothesis is that autistic spectrum disorders involve a lack or deficiency in Theory of Mind, sometimes called mindblindness.

The ability to understand what other people experience the world differently than you do. That they have different thoughts, beliefs and desires. That they know things you do not know and visa versa. And that, people can be deceived.

Children with autism, Trevarthen et al A philosophical concept of the understanding one has that another person has an individual perspective on states of affairs, that this consciousness depends in part on information which they may have which is not available to oneself and vice versa.