The autism spectrum is a continuum of mild to severe impairment in the domains of social communication and restrictive repetitive behaviors and interests. It is not coextensive with the range of possible cognitive dispositions. The introduction of autism spectrum disorder in the DSM-V was meant to collapse hard-and-fast distinctions between what were previously classified as four distinct disorders (autistic disorder, Asperger's disorder, childhood disintegrative disorder, and pervasive developmental disorder). It does not recast autism as just another shade of normal.