Autism and Repetitive behavior

Sleeping boy beside a dozen or so toys arranged in a line
A young boy with autism who has arranged his toys in a row
Autistic individuals can display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R) categorizes as follows.

Stereotyped behaviors: Repetitive movements, such as hand flapping, head rolling, or body rocking.
Compulsive behaviors: Time-consuming behaviors intended to reduce anxiety that an individual feels compelled to perform repeatedly or according to rigid rules, such as placing objects in a specific order, checking things, or hand washing.
Sameness: Resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
Ritualistic behavior: Unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual. This is closely associated with sameness and an independent validation has suggested combining the two factors.
Restricted interests: Interests or fixations that are abnormal in theme or intensity of focus, such as preoccupation with a single television program, toy, or game.
Self-injury: Behaviors such as eye-poking, skin-picking, hand-biting and head-banging.
No single repetitive or self-injurious behavior seems to be specific to autism, but autism appears to have an elevated pattern of occurrence and severity of these behaviors.