An investigation of the phenotypic and etiological relationships between autism and specific language impairment

Research output: ThesisDoctoral Thesis

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[Truncated abstract] Recent findings that a subgroup of children with Autism Spectrum Disorder (ASD) has structural language deficits reminiscent of Specific Language Impairment (SLI) have led some authors to claim that there is substantial shared etiology in these two conditions (Kjelgaard & Tager-Flusberg, 2001). A competing explanation is that the overlap between ASD and SLI is superficial (Whitehouse, Barry, & Bishop, 2007; Williams, Botting, & Boucher, 2008). While considerable research has examined overlap in the language phenotypes of ASD and SLI, limited attention has been paid to overlap in the cognitive domain. Therefore, the aims of this thesis were to (1) investigate possible points of overlap in the cognitive phenotypes of ASD and SLI, and (2) explore possible shared heritable risk factors for ASD and SLI in parents of both groups of children. The introductory chapters of this thesis comprise two literature reviews. Chapter 1 reviews the empirical literature that has investigated etiological overlap in ASD and SLI, covering the realms of language, behavior, molecular genetics, neurobiology and family studies. Chapter 2 presents a more focused review of the literature that has explored whether children with SLI carry any of the cognitive characteristics of ASD. These reviews present the theoretical background relevant to the empirical work that forms the body of this thesis. The relationship between ASD and SLI was investigated in a series of four studies. The first two studies compared children with ASD (N = 32) to children with SLI (N = 19) and typically developing children (TD; N = 61) on measures sensitive to the cognitive phenotype of ASD (the Children's Embedded Figures Test and an emotion recognition task) and language markers of SLI (nonword and sentence repetition tasks). The "language impaired" children with ASD (ALI group) and the children with SLI performed worse than expected based on their age, sex and nonverbal ability on the nonword and sentence repetition tasks. The ASD children who had language ability within "normal" limits (ALN group) demonstrated intact performance on these tasks. In addition, the SLI group was slower and less accurate than expected to complete the Children's Embedded Figures Test (CEFT). All of the clinical groups performed worse than predicted when identifying complex emotions (surprised, disgusted) from faces and from voices. The ALI and SLI groups also had difficulty identifying the simple emotions (happy, sad, scared, angry) across the visual and auditory modalities...
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2013


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