Objectives: We used a systematic observation methodology to investigate the presence of RRBs in preschool children with and without ASD at three timepoints during 13 months of development. We predicted that at all timepoints children with ASD would demonstrate elevated levels of RRBs. Continued elevated rates of RRBs were expected in the ASD group, but reduction over time in TD. We hypothesised that a higher incidence of RRBs would correlate negatively with non-verbal development and language, but positively with ASD severity.
Methods: 49 children (mean age at T1 = 44.5 months, SD = 8.53) with ASD were matched to 45 TD children using non-verbal development scores. Children also completed measures of language and play. ASD children completed the ADOS and their parents the ADI-R. Observational coding of RRBs was based on items used in the Repetitive Behaviour Questionnaire (Turner, 1999), DISCO (Wing et al, 2002) and by Watt et al (2008). All RRBs observed within a 10 minute free play session were coded using Noldus Observer.
Results: Significantly more RRBs were observed in the ASD group than the TD group at all timepoints. Children with ASD showed a slight increase in the number of RRBs over time; however change scores were non-significant. TD children demonstrated a slight increase in RRBs at T2 followed by a decrease at T3. The change between T2 and T3 approached significance (t = 11.96; p = .057). Despite group differences in RRBs, there was no difference in the rate of change in expression of RRBs. At all three time points, total RRBs correlated negatively with non-verbal development and language irrespective of group. No association was found with ASD severity.
Conclusions: This study supports the view that whilst RRBs are evident in TD, these are less than in preschool children with ASD. In ASD the frequency of behaviours remained constant and did not reduce. Change rates between the two groups, despite the difference in T1 scores, were similar with both groups changing at the same rate. In keeping with the findings of Bishop et al (2006) and Militerni et al (2002), non-verbal development and language associated negatively with heightened RRBs totals. These associations were present in TD children. The lack of association with ADOS algorithm scores is suggestive that RRBs are dissociable from social and communication deficits in ASD.
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