Linguistic abilities in children with autism spectrum disorder.

Background: Two broad approaches have been used to examine linguistic skills in Asperger syndrome (AS) and high functioning autism (HFA). One approach has aimed at determining the external validity of each diagnosis by investigating whether developmental language history, which differentiates AS from HFA, is relevant in long-term linguistic outcomes. An alternative approach, viewing AS and HFA as presentations on an autism spectrum (ASD), has investigated subgroups within the spectrum based on linguistic performance. Neither approach, however, has provided an in-depth description of the linguistic difficulties experienced in ASD necessary for therapy planning. Purpose: To provide clinically applicable research findings to extend the clinical understanding of the linguistic difficulties in ASD by: (1) comparing the linguistic skills in ASD with those of normally developing controls; (2) comparing the linguistic skills of children with ASD re-classified as AS and HFA using DSM-IV language criterion; (3) documenting the heterogeneity within a group of children with ASD by investigating within-group differences. Methods and procedures: Twenty children (aged 9; 0-17; 1 years) with a diagnosis of ASD were assessed using the Clinical Evaluation of Language Fundamentals-Fourth Edition (CELF-4) and the Test of Nonverbal Intelligence-Second Edition (TONI-2). Performance by ASD participants was compared to typically developing peers. Re-classification of individuals with ASD as AS or HFA was undertaken using DSM-IV language criterion to determine between-group differences on linguistic measures. Hierarchical cluster analysis was undertaken using the ASD performance on the CELF-4 to examine within-group differences based on linguistic abilities. Outcomes and results: There were significant differences between the ASD children and normally developing peers on a range of linguistic measures. There were no significant differences between the children re-classified as AS and HFA on the comprehensive linguistic assessment. Subgroups within ASD, based on linguistic performance, could be identified. Conclusions and implications: Collectively, the children with ASD in the study had a range of compromised linguistic skills relative to their peers. Children re-classified as AS could not be differentiated from children re-classified as HFA on current linguistic performance. An examination of subgroups of ASD participants revealed the heterogeneous nature of the linguistic skills associated with ASD, where linguistic proficiency ranged from above average performance to severe difficulties. The results of the study are discussed in terms of the clinical applicability of the findings