Theory of mind means the ability to understand that others have beliefs, desires and intentions that are different from one's own.
Theory of mind appears innately in most people, appearing in childhood and developing throughout adulthood. Different people are different in their ability to understand other people's thoughts.
It is often implied or assumed (but not stated explicitly) that this does not merely signify conceptual understanding "other people have minds and think differently than I do", but an understanding of the depth and significance that other people's thoughts have. It is related to empathy.
Some autistic people are impaired in terms of theory of mind. In 1985, Simon Baron-Cohen, Alan Leslie and Uta Frith published an article called "Does the autistic child have a theory of mind?" in which it was suggested that children with autism have particular difficulties with tasks requiring the child to understand another person's beliefs. These difficulties persist when children are matched for verbal skills (Happe, 1995, Child Development) and have been taken as a key feature of autism.
Sometimes, autistic people have a solid understanding of theory of mind, but continuously misread others because they have difficulty interpreting nonverbal cues.
Teaching Theory of Mind
Parents can foster theory of mind by encouraging their impaired children to think about other people's feelings in stories and playtime. During reading, parents can ask questions like "How do you think the prince feels when he sees the princess coming to save him?" or "Did the princess see the witch start the fire?"
Autistic adults have recommended the show My Little Pony (available on Netflix and Discovery Family) for demonstrating social skills and theory of mind in an entertaining way.
When Theory of Mind Isn't The Problem
Sometimes parents and caregivers believe that an autistic person lacks theory of mind, when in fact the person clearly understands that different people think differently. Autistic people sometimes struggle to anticipate other people's thoughts.
One autistic teenage girl describes it this way: "The human brain is incredibly complex. How am I supposed to take something as nuanced as another person's mind and predict the way it would react in a certain situation? I'm no supercomputer!"