Defining the behavioral phenotype of Asperger syndrome.

Asperger syndrome (AS) is characterized by social deficits and restricted interests in the absence of mental retardation and language delay. However, it is unclear to what extent the social deficits of AS differ from those of traditional autism. To address this issue, 58 subjects with AS were compared with 39 subjects with autism. Social deficits were classified according to Wing and Gould's method. Forty-six (79%) subjects with AS were rated as active but odd, while 32 (82%) with autism were described as aloof and passive, while a few subjects showed mixed features. Thus, despite the overlap between AS and autism, subjects with AS showed a distinct pattern of social impairment. Implications of these findings are discussed.