Classic autism is part of the autism spectrum disorder of developmental disability, and is the most severe disability in this spectrum. Parents typically notice the first signs before the child is 3 years old, presenting as difficulties involving social interaction and communication.
A child with classic autism may not respond to people and may avoid eye contact. He may be withdrawn and seem unable to play normally with other children.
Children with classic autism may focus on one item for abnormally long periods of time, and be fixated on a very narrow range of objects and interests.
An autistic child may be very inflexible about routines and engage in ritual behaviour. For instance, she may insist on having a certain type of food at every meal. She is likely to become upset at changes in her environment.
Many children with classic autism are unusually sensitive to sensory stimulation, making them avoid or become upset at loud sounds, bright lights, or being hugged or touched.
Performing repetitive movements is a sign that a child has classic autism, such as rocking, flapping arms, or hitting himself over and over. The child also may use language in a very repetitive or sing-song manner.