Written and oral language in autism

Autism spectrum disorders (ASD) are a group of childhood developmental disorders characterized by delayed and deviant language, repetitive behaviors, and impaired social development (American Psychiatric Association, 1994). Estimated prevalence rates for autism, the most severe form of these disorders, are 1 in 166 (Fombonne, 2005), and the incidence of ASD is thought to be increasing (Newschaffer and Curran, 2003). ASD, by definition, include a wide range of levels of language functioning. ^ Language impairments are a significant diagnostic component of many developmental disorders; however, understanding the neurobiological underpinnings of developmental language difficulties remains elusive. Neuroanatomical and genetic data have suggested a relationship between ASD and developmental language disorder (DLD), and clinically, the differential diagnosis between DLD and ASD, especially high-functioning autism (HAD), is often difficult (Rapin, 1996). The robust association between developmental disorder and language impairment begs an understanding of the nature of their relationship. ^ Few studies have explored the heterogeneity of language skills in children with ASD (e.g., Rapin, 1996; Tager-Flusberg, 2003). Writing is a complex linguistic process, and there have only been a few studies concerned with written language abilities in HAD. The current study investigates several domains of language functioning, with a focus on written language in HAD and DLD. ^ In the current study children with HAD demonstrated spared writing skills, single-word reading and decoding, and impaired reading comprehension relative to the DLD group. These findings are consistent with those reported by Rapin (1996) suggesting that the preserved written language and severely affected aural comprehension exhibited by children at preschool age continues a similar developmental trajectory into school age. Results from the current study also suggest that while the children with HAD exhibited impaired listening and reading comprehension abilities, relative to the children with DLD, their deficits were dissociable between procedural and mechanical, and complex skills in both areas. Overall, results from the current study are consistent with the proposal of Minshew et al. (1995) that the language development profile of children with HAD is dissociable between spared procedural and mechanical abilities, and impaired complex skills across both oral and written language.