Hemispheric asymmetries and early infantile autism

The observation that language disorders constitute a major symptom of early infantile autism has led some researchers to speculate that the autistic syndrome may be a result of brain damage to the left hemisphere. Such speculation has fostered a number of studies in which attempts have been made to link autism with ostensibly positive signs of left hemisphere damage, such as left-handedness and preferences for "right hemisphere" functional and cognitive activities. In the present review, contributions to this area are systematically reviewed. Studies attempting to demonstrate that an unusually high incidence of left-handedness occurs in autistic samples are examined. Functional and morphological studies examining patterns of asymmetry in autistic samples are reviewed. It is shown that most studies on handedness fail to account adequately for the role that age of subjects may play in the manifestation of left-handedness. A simple cause-and-effect model of abnormal cerebral asymmetry and autism is rejected in favor of a more integrative yet parsimonious model that specifically attempts to explain the language disorder common to autism.