ABSTRACT
This chapter describes the authors’ own programs of research, each of which is focused on the language development of a particular neurodevelopmental disorder, namely, autism and fragile X syndrome. Autism is a neurodevelopmental disorder, probably present from birth, that is identified on the basis of a triad of behavioral characteristics including impairments in communication and social reciprocity and the presence of unusually repetitive or stereotyped behaviors and interests. Most children with autism spectrum disorders have delays in language development relative to their nonverbal mental ages and approximately half of young children with autism fail to acquire speech as their primary mode of communication. Fragile X syndrome is the leading inherited cause of mental retardation. There are several features of the behavioral phenotype of fragile X syndrome that according to the Child Talk model would be expected to negatively affect language learning and use and distinguish it from other neurodevelopmental disorders.
