Imitation performance in preschoolers referred for autism spectrum disorders (ASD): A comparison between true cases and false positives

Background:
Over the last 35 years, researchers consistently reported imitation impairments in young children with ASD. Nevertheless, differential diagnostic aspects of imitation have not yet been studied with a multidimensional imitation test.

Objectives:
To explore imitation abilities in young children suspected of ASD, using the Preschool Imitation and Praxis Scale (PIPS) and to compare imitation to other developmental domains.
Methods:
Seventy-one preschoolers (CA: M=40.5m, range 23-54m, IQ above 70) suspected of ASD and referred to University Autism Clinics (Belgium) were divided in two groups according to their ADOS-G classification: 48 children with ASD (19 with autistic disorder AD and 29 with PDD-NOS) and 23 children without ASD. Children were age-matched and assessed on five developmental domains: cognition (Bayley, SON-R), gross motor (PDMS2-locomotion), fine motor (PDMS2-visuomotor), language reception (RTOS, CDI) and imitation (PIPS). The PIPS is a newly developed instrument to measure meaningful and non-meaningful procedural and single and sequential bodily imitation. Age norms were derived from PIPS scores of 498 typically developing children. Results:
Within-group analyses revealed that both groups performed less well than expected for their chronological age on all developmental domains, with the exception of language reception in children without ASD and mental age in children with ASD. Between-group analyses revealed that children with ASD performed significantly poorer compared to children without ASD on imitation (p<0.05), gross motor (p<0.05) and receptive language tasks (p<0.05). Sub analysis revealed that children with PDD-NOS and AD did not differ from each other on the five developmental domains, with the exception of sequential bodily imitation (p<0.05).

Conclusions: This study is the first to investigate imitation abilities in young children suspected of ASD with a standardised multidimensional imitation test: The Preschool Imitation and Praxis Scale (PIPS). Findings of this study indicate that the investigation of imitation can contribute to the diagnosis of ASD.