Background: Siblings of children with autism spectrum disorders (ASD) have higher prevalence of ASD with a recurrence of 19%. Children with ASD demonstrate significant impairment in all types of imitative skills. Imitation is markedly developed in the first few years of life; therefore, a study of imitation in younger siblings in this period may reveal early deviation.
Objective: To study the development of imitation skills from 9- to 18-months, specifying types of imitation, in siblings of
children with ASD compared with typically developing children.
Method and Material: A longitudinal case-control study was conducted on eight siblings of children with ASDs and nineteen typically developing children who were age- and gender-matched. Data collection consisted of parental recording of emerging imitative abilities and structured direct observation of imitative skills at 9, 12 and 18 months. Three types of imitative skills were targeted including vocal, object and gesture imitation.
Results: The development of vocal imitation in siblings of children with ASD between 12 to 18 months was delayed in
comparison with typically developing children with significant statistical difference at 18 months. Object and gesture imitations were not significantly different between the two groups.
Conclusion: Siblings of children with ASDs had some delays in vocal imitation skills at the age of 12 to 18 months, compared with typically developing children.

Keywords: Imitation, Sibling, Autism, Autism spectrum disorder