Those who do speak often use language in unusual ways or may seem unable to combine words into meaningful sentences. Some speak only single words, while repeat the same phrase no matter what the situation. Still other children with autism display echolalia . People with autism also tend to confuse pronouns. Although children with autism usually appear physically normal and have good muscle control, odd repetitive motions may set them apart from other children.
Experts call such behaviours stereotypes or self-stimulation.
Some people with autism also tend to repeat certain actions over and over or may develop troublesome fixations with specific objects. For unexplained reasons, people with autism demand consistency in their environment. For example, many insist on eating the same foods, at the same time, sitting at precisely the same place at the table every day. They may get furious if a picture is tilted on the wall, or wildly upset if their toothbrush has been moved even slightly. A minor change in their routine, like taking a different route to school, may be tremendously upsetting.