Objectives: The purpose of this study was to examine differences in IS in children with and without ASD, and to investigate the relationship between IS and social communication functioning.
Methods: Participants were 111 children, aged 4 to 8 years, participating in a longitudinal study of child development beginning in infancy. Children with ASD (n=44; mean age=5.5 years; mean NVIQ=98) and without ASD (n=67; mean age=5.2 years; mean NVIQ=109) were included. The non-ASD group had significantly higher NVIQ than the ASD group (p<0.001). Children with ASD whose NVIQ was below 70 were excluded from the analysis.
IS was assessed using an adaptation of Hobson and Lee’s (1999) paradigm. Examiners demonstrated the novel use of four sets of objects in randomly varying order across subjects. Following a 10-minute interval, children were instructed to “use” the objects. Sessions were videotaped and later coded blind to group membership. To measure IS, a ‘matching score’ was generated for each task on a five point scale, with higher scores reflecting a greater quality in degree of matching the examiner’s movements. The IS dependent variable was calculated by summing the scores for all four tasks. Other dependent variables included the Stanford-Binet V nonverbal IQ score (NVIQ) and the Social +Communication algorithm score from the Autism Diagnostic Observation Schedule.
Results: The ASD group was significantly less likely than the non-ASD group to match the quality of the examiner’s actions [ t(2,109)=-2.05, p<0.05]. Within group correlational analyses using NVIQ and social communication scores determined that NVIQ was not correlated with IS in either group. However, IS was significantly negatively correlated with social communication scores (lower scores indicate less impairment) for the non-ASD group only [r(67) = -0.26, p < 0.05]. Given this finding, we hypothesized that fine motor difficulties may interfere with IS in the ASD group. Using the Mullen Fine Motor standard score obtained from the subjects’ 36-month assessment, we found that fine motor functioning at 36 months of age predicted future IS performance in the ASD group only [F (1,43) = 4.4; p < 0.05].
Conclusions: Consistent with previous research, children with HFA demonstrated IS impairments as compared with children without ASD. Contrary to other studies, nonverbal IQ was not related to IS in either group of children and social communicative functioning was related to IS in the non-ASD group only. For the ASD group, fine motor difficulties at 36 months of age predicted IS impairment at a later age. Thus, this study suggests that motor skill impairments may adversely affect IS in children with HFA.