a pediatric medical geneticist— all of whom were experienced in autism. Following review of case material the panel discussed the case until a consensus diagnosis was obtained. Only those cases in which a consensus diagnosis of autism was reached were included (4) Minimal developmental level of 18 months as determined by the Vineland Adaptive Behavior Scale (VABS) (Sparrow, Balla & Cicchetti 1984) or the VABS-II (Sparrow, Cicchetti & Balla 2005) or IQ equivalent > 35. These minimal developmental levels assure that ADI-R results are valid and reduce the likelihood of including individuals with severe mental retardation only. We excluded participants with severe sensory problems (e.g., visual impairment or hearing loss), significant motor impairments (e.g., failure to sit by 12 months or walk by 24 months), or identified metabolic, genetic, or progressive neurological disorders.
