which functional impairment becomes obvious will vary according to characteristics of
the individual and his or her environment. Co re diagnostic features are evident in the
developmental period, but intervention, co mpensation, and current supports may mask
difficulties in at least some contexts. Manifestations of the disorder also vary greatly de-
pending on the severity of the autistic condit ion, developmental level,  and chronological age;
hence, the term spectrum. Autism spectrum disorder enco mpasses disorders previously re-
ferred to as early infantile  autism, childhood autism, Ka nner’s autism, high-functioning
autism, atypical autism, pervasive developmen tal disorder not otherw ise specified, child-
hood disintegrative disorder , and Asperger’s disorder.
The impairments in communicat ion and social interaction specified in Criterion A are
pervasive and sustained. Diagnoses are most  valid and reliable when based on multiple
sources of information, including clinician’s observations, caregiver history, and, when
possible, self-report. Verbal and nonverbal deficits in social communication have varying
manifestations, depending on the individual’s age, intellectual level,  and language ability,
as well as other factors such as treatment history and current support. Many individuals
have language deficits, ranging from complete lack of speech through language delays,
poor comprehension of speech, echoed speech, or stilted  and overly literal language. Even
when formal language skills (e.g ., vocabulary, grammar) are intact, the use of language for
reciprocal social communication is im paired in autism spectrum disorder.
Deficits in social-emotional reciprocity (i.e.,  the ability to engage with others and share
thoughts and feelings) are cl early evident in young children with the disorder, who may
show little or no initiation of social interaction and no sharing of emotions, along with re-