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The structural language skills of preschool aged children with autism
thesisposted on 09.02.2017, 05:55 by Park, Carlie Jane
The aim of this thesis was to explore the structural language skills of preschool aged children with autism. Autism is a Pervasive Developmental Disorder defined by impairments in social interaction and communication, and restrictive and repetitive behaviours (American Psychiatric Association, 2000). Structural language skills were identified as an important area for investigation as the delay or absence of language development is an important diagnostic and clinical feature of autism. For example, approximately 50% of young people with autism never develop functional language skills (Howlin, 2005; Tager-Flusberg, Paul, & Lord, 2005), and for the 25% to 30% of the population with autism who develop fully fluent language skills (Minshew, Goldstein, & Siegel, 1995), the majority have ongoing difficulties in using their language skills within a social context (Bartak, Rutter, & Cox, 1975; Rice, Warren, & Betz, 2005; Tonge & Rinehart, 2007). In the long term, the development of some functional language by the age of five is one of the strongest predictors of positive outcomes in adulthood (Howlin, 2005; Pierce & Bartolucci, 1977; Rutter, 1978; Tager-Flusberg, 2000). Despite the importance of language development for a child with autism and their families, relatively little is known about the structural language skills of children with autism. The first chapter of this thesis presents a thorough review of the literature on the language skills of children with autism with the aim of identifying areas requiring further investigation. It was found that previous research on the language skills of children with autism has tended to focus on pragmatic deficits and/or functional language skills with relatively fewer studies investigating structural language skills. Research has been particularly lacking in the area of morphology and syntax in autism with the majority of the literature being over 20 years old and thus requiring replication with current diagnostic criteria and assessment tools. Other weaknesses of this literature are the use of inconsistent methodologies, the investigation of a narrow range of linguistic skills, a lack of studies investigating language skills at specific developmental stages, and the exclusion of children with autism with an intellectual disability and/or those with poor expressive language skills, and females with autism. Partly as a result of these limitations, and also due to the heterogeneity of language presentation within the population with autism, we do not yet have a clear description of the profile of structural language skills in autism, and how these skills might relate to other areas of functioning. To address the limitations of the previous literature, the current research aimed to investigate a range of different language skills within a group of preschool aged children with autism and comparison groups of children with specific language impairment, developmental delay without autism, and typically developing children. Children with autism were selected for the study who were both high functioning and had developmental delay. Participants were aged from 3.5 to 6 years. Three studies were conducted which have been presented in chapters 3 to 5 as submitted journal papers. The first study investigated the profile of language strengths and weaknesses in preschool aged children with autism. This included an investigation of whether the language profile which presents in autism is specific and unique to that disorder and whether there are differences in this language profile across gender and intellectual functioning. Participants were 63 children who had high functioning autism (n=17), autism with developmental delay (n=10), developmental delay without autism (n=10), typical development (n=20), and specific language impairment (n=6). They were administered a series of standardised tests of structural language skills. It was found that the group with high functioning autism had a unique profile of language skills compared to the other groups; a relative (but not absolute) strength in expressive vocabulary skills compared to receptive vocabulary skills. This strength was not shared by children with autism with an intellectual disability, and no gender differences in language profiles were found. The second study investigated whether children with autism have atypical development of morphological and syntactic skills, including whether they use rote learning to compensate for impaired morphological processing, and acquire grammatical morphemes in an atypical order. Participants were children who had autism (n=17), developmental delay without autism (n=7), and typically developing children (n=19). Speech samples were obtained from participants during the administration of the Autism Diagnostic Observation Schedule, and transcripts were coded using the Index of Productive Syntax and for usage of Brown’s (1973) Grammatical Morphemes. Participants were also administered an elicitation task requiring the application of inflections to non-words; the Wugs Task. The main finding of this study was that across both morphological and syntactic skills, children with autism have subskills which are a combination of intact, delayed, and atypical. The third study investigated the relationship between structural and functional language skills, autism symptom severity, adaptive behaviour, and emotional and behavioural problems in preschoolers with autism. Participants were children with autism (n=27), and two comparison groups of children with developmental delay without autism (n=12), and typically developing children (n=20). The participants were administered standardised tests of structural language skills and the Autism Diagnostic Observation Schedule. Parents completed the Vineland Adaptive Behavior Scales and the Developmental Behaviour Checklist. Results indicated that for children with autism, functional language skills were associated with structural language, social and daily living skills, and some behavioural problems, but not autism symptom severity. There was some evidence that structural language skills were associated with social skills for children with autism, but not with daily living skills, emotional and behavioural problems or autism symptom severity. The majority of these associations were not found to be specific to autism. The results of this study suggest that it is important to consider the structural language skills of children with autism, and to develop specific interventions to address difficulties in this area. The discussion chapter discusses the clinical implications and future research directions generated by this research, and the limitations of the research. The findings of these three studies highlighted that preschool aged children with autism have a complex developmental profile of structural language skills with a mixture of intact, delayed and atypical skills. The findings also highlighted that structural language skills develop somewhat separately to the core symptoms of autism and behavioural problems. Collectively these findings suggested that clinicians need to conduct a comprehensive assessment of the structural language skills of children with autism and not make assumptions about their language skills based on behavioural presentation. Furthermore, in order to maximise language development in the preschool years, structural language interventions need to be tailored to the strengths and weaknesses of each individual child with autism. The main limitation of this research was small sample sizes for the lower functioning groups. This limitation was address by combining or removing groups for specific analyses, and higher the need for replication with larger samples where warranted. Future research directions include investigating whether echolalia may create a relative strength in expressive vocabulary skills for children with high functioning autism, and further investigation of the pattern of strengths and weaknesses found in morphology and syntactic skills for preschool aged children with autism. This research has been able to add to our understanding of the nature of structural language skills in preschool aged children with autism and provide information to assist clinicians to maximise language development, thereby optimising outcomes for individuals with autism in their adult years.