Repetitive behaviours are one of the defining features of autism. Research suggests two groupings: ‘low-level’ (eg. repetitive motor movements) and ‘high-level’ (eg. insistence on sameness), and that the range and severity of repetitive behaviours are related to age and cognitive ability. Repetitive behaviours are also commonly seen in typically developing young children, but are they the same or different?
The aim was to compare the frequency and factor structure of repetitive behaviours in typically developing children and children with autism/ASD, at a comparable language level.
Eleven items from the Repetitive Behaviours Questionnaire (RBQ2 - Leekam et al 2007) had been answered by parents in two studies. Study 1 included 53 children (31 Autism, 22 ASD) aged between 35 and 67 months. Study 2 included 192 typically developing (TD) children aged 24 to 28 months.
Principal components analysis showed a similar two-factor structure for the TD and Autism/ASD groups. The Repetitive Motor Behaviours Factor accounted for a larger proportion of the variance in responses from the TD group than the Autism/ASD group (33% vs 19%) and vice versa for the Rigidity/Sameness Factor (TD 16% vs Autism/ASD 34%).
The TD and Autism/ASD groups did not differ in frequency and severity of their repetitive behaviours for either factor. Age and better language were related to more high-level behaviours in the TD group, but not in the Autism/ASD groups.
Repetitive behaviours seem to be much the same in children with autism as they are in TD children at two years of age. The difficulty for families lies in the degree to which these behaviours continue long after the "terrible twos". The findings reinforce the suggestion that repetitive behaviours may not act as early diagnostic markers, though more research is required on infants with autism before the age of two.