Repetitive behavior in children with autism spectrum disorder (ASD) is associated with developmental age and communication abilities (Lam et al., 2008). It has been hypothesized that the relation between development and repetitive behavior may be a result of the changing nature of repetitive behaviors with more motor stereotypies seen in lower functioning children (Bishop et al., 2006, Lewis & Bodfish, 1998,). However, it is possible that changes in specific developmental abilities may predict declines in repetitive behavior. Increased repetitive behavior has been observed in linguistically complex environments such as classrooms and unfamiliar social situations. Therefore, it is logical to question whether specific language abilities are related to repetitive behavior in children with ASD.
1. To examine whether general language ability is related to repetitive behavior in children with ASD.
2. To examine whether one aspect of language, specifically grammar understanding, is related to repetitive behavior and mediates the relation between general language ability and repetitive behavior.
Verbal ability and repetitive behaviors were assessed in 47 children with high functioning ASD (mean age = 10 years, 9 months) and 55 children with typical development (mean age = 9 years, 8 months). General language ability was measured by the raw score on the verbal subtest of Kaufman Brief Intelligence Test – 2 (KBIT-2). Groups were matched on general language ability. Grammar understanding was measured by the Test of Receptive Grammar (TROG; Bishop, 1989). The TROG measures understanding of grammar including morphological and lexical structure. Repetitive and compulsive behaviors were measured by The Childhood Routines Inventory (CRI; Evans, 1997).
K-BIT verbal raw score was correlated with the CRI total score (r = -.30; p < .05) indicating that poorer general verbal ability was linked to higher levels of repetitive behavior. Additionally, the TROG total number correct was negatively correlated with the CRI (r = -.41; p < .001) indicating that poorer understanding of linguistic structure was related to higher levels of repetitive behavior. Unsurprisingly, the two language measures, the KBIT-2 and TROG were highly related (r = .70; p < .001). To examine whether grammar understanding independently contributed to repetitive behavior, a mediation analysis was conducted. To test for mediation, both the KBIT-2 and the TROG were used as predictors of the total score on the CRI. A Sobel test was conducted and indicated that the TROG fully mediated the relation between KBIT-2 verbal raw score and the CRI. However, when verbal raw score was treated as a mediator of the relation between the TROG and the CRI, it had no mediating effect.
Results suggest that grammar understanding is specifically related to repetitive behaviors in children with ASD. Independently of overall verbal ability, poor grammar understanding was related to increased repetitive behavior. Results suggest that the inability to understand and integrate complex linguistic information may drive the need for repetition and routine in one’s environment. These results offer an intriguing notion that improved interpretation of linguistic structures early in life may lead to decreased repetitive behavior in autism.
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