Childhood autism (sometimes called pervasive developmental disorder) is characterized by a profound difficulty in social relationships. A disorder that appears in early childhood-generally by age three-autism is not completely understood by researchers but is likely to be due to abnormal brain development. The disorder differs from child to child, but autism may be first suspected when an infant or toddler fails to develop normal social interactions, such as eye contact with parents. When in the company of others, autistic children may display repetitive movements such as rocking, head banging, or hand twisting. These children also exhibit markedly delayed language or unusual language use, avoidance of eye contact, obsession with order and sameness and an aversion to or lack of interest in other persons.
Autism is a rare disorder, occurring in perhaps one in 10,000 births. It can be confused with a form of mental retardation caused by a genetic disorder, fragile X syndrome, because many symptoms overlap. Research has attempted to characterize the central disorder of autism: is it a cognitive, social, or linguistic deficit? Compounding the picture is the fact that many autistic children are also retarded, though some show normal intelligence on non-verbal tests.
Approximately 50% of autistic children never learn to talk, or they talk in only the most rudimentary way. Six is the crucial age in this regard, after which the prognosis for dramatic language progress looks bleak. Rigorous behavioral intervention at an early age can often provide such children with a form of communication. Educational programs are willing to try any medium that the child can succeed with: speech, gesture, "communication boards" on which the child may point to pictures or symbols, signed languages and so forth. In the 1990s, there was interest in reaching autistic children via "facilitated communication" in which the child is "helped" by a facilitator's touch to type on a keyboard. This method raised the hopes of many parents and teachers who work with autistic children. However, careful evaluation of the outcomes suggests that the dramatic successes are mostly illusory, and that the child's elaborate, seemingly spontaneous productions were in fact guided unknowingly by the facilitator.
"High-functioning" autistic children can learn to talk, but several features of their language have been highlighted as aberrant. A marked feature of autistic speech is echolalia, which is an immediate or delayed repetition of the content and form of another person's speech. The function of echolalia has recently been reevaluated. New evidence suggest it may be a way for the child to enter or maintain a conversation in the face of poor spontaneous language skills. The autistic child is more prone to make pronoun substitutions, such as you for I. The child will say such things as:
"You stay here," or "You want a hot dog."
Normal two-year-old children speak this way as well, but only fleetingly. In terms of lexical (vocabulary) development, substantial differences do not seem apparent in the type or variety of vocabulary in normal IQ autistic children. An exception is the autistic child's vocabulary referring to emotions or mental states, such as think, believe, and know, which is generally impoverished or underdeveloped. Grammar and morphology (inflection and word formation) seem to be developed in an essentially normal way. However, in the area of conversational development, the peculiarities of autism are revealed.