Baker (1980) found that those showing evidence of delayed language acquisition tended to be found either mentally retarded or autistic. More than half of those who had acquired language but exhibited other symptoms of neuropsychiatric dysfunction tended to be diagnosed with ADD. However, an extra problem of diagnosis has been asserted in the case of language-related disorders, which are more difficult to identify than such conditions as Down syndrome and mental retardation (Freedman, 1995).
Distinction between directed or intelligent thought, and undirected or autistic thought, appears to have been made in general terms by Bleuler in 1912. Directed thought is conscious and can be communicated by language. Autistic thought is subconscious and is (typically) incommunicable by language, whether spoken or unspoken. Over the course of the twentieth century, the definition has been refined, and autism exhibits a variety of symptoms. However, language acquisition problems, as well as cognitive problems, are important features of diagnosis. In particular,
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