Imitation plays a significant role in the early social development of infants and toddlers. Impaired performance in a range of imitation tasks has been described in children with autism spectrum disorders (ASD). Several possible mechanisms underlying imitation deficits in ASD have been proposed. Of these, the extent of social-reciprocal interaction and responsiveness deficits, cognitive level and motor development problems appear to affect imitation development the most.
Objectives:
1.To examine whether imitation abilities in ASD correlate with autism severity and gross and fine motor skills. 2. To examine imitation abilities in children with ASD by comparing their performances in two imitation types i.e. body movements and 'action on objects, using meaningful and non-meaningful tasks. 3. To evaluate whether performance in these four imitation situations is related to the severity of autism symptoms or to motor abilities.
Methods: Twenty-five children aged 32-51 months (M=40.0, SD=5.7) were diagnosed with autism (23) and ASD (2) using the Autism Diagnosis Interview-Revised and the Autism Diagnosis Observation Schedule (ADOS). Autism severity was evaluated using The ADOS new algorithm and the socio-communication total scores and repetitive and restrictive behaviors (RRB) total scores. Cognitive abilities were assessed using the Mullen scales; gross and fine motor skills were examined by the Peabody Developmental Motor Scales; and imitation abilities were assessed using items from the Motor Imitation Tasks (MITs).
Results: Controlling for cognitive level, the new ADOS algorithm that measures overall severity of autism symptoms correlated significantly only with meaningful imitation situations. Looking at the specific autism domains, imitation abilities in all four situations correlated significantly only with socio-communication deficits and not with RRB scores. Gross and fine motor abilities were generally below average in the examined group and did not correlate with imitation abilities or with autism severity. Comparison of the four imitation situations revealed that performances of meaningful actions were better than non-meaningful actions (p<.001), and imitation of 'action on objects' was better than imitation of body movements (almost reaching significance). When the entire group was divided into two autism severity subgroups, low and high ADOS groups (based on the new ADOS algorithm median scores), a significant autism severity effect (p<.05) was found. The group with less severe impairments had better imitation scores than the group with more severe autism symptoms. No autism severity x imitation situation interaction was found, meaning that the low ADOS group performed better than the high ADOS group in all the imitation situations.
Investigating the differences in imitation abilities of low and high gross and fine motor skills groups (scores above or below the median on the Peabody Motor scales), revealed no gross or fine motor ability effects on imitation skills.
Conclusions:
Imitation is a complex developmental skill that requires intact motor, cognitive and social abilities. The present results suggest that out of several possible mechanisms that could underlie imitation deficits in ASD, the social reciprocal impairments are mostly associated with imitation performance.