Even though autism is a relatively infrequent disorder, occurring in about 1.5 to 2 cases/1000 in the population (Sugiyama and Abe, 1989), it has attracted the attention of many researchers since the time of Kanner's (1943) initial description of the syndrome. This curiosity reflects, in part, the fact that the bizarre and puzzling behaviors shown by individuals with autism present a challenge to theorists. More urgently, the fact that age-appropriate learning and social–communicative behavior is not present in these children has a devastating impact on their families and on the children's later social, emotional and cognitive development. Understanding the biological mechanisms responsible for autism may help to shed light on the best way to treat this syndrome.

Autism has an age of onset that is, typically, between 12 and 30 months of age, although some mothers report noticing abnormalities in their child's behavior from birth. The first behavioral disturbances noted include lack of response to the child's name being called, acting as if deaf, despite other evidence of apparent normal hearing (e.g., dashing to the kitchen from another room when a candy bar is unwrapped); failure to anticipate being picked up; failure to cuddle when held; poor eye contact and lack of interest in social interaction; failure to use normal gestures such as pointing to communicate (instead pulling others to desired objects);