International Meeting for Autism Research: Imitation In a Large Cohort of Preschoolers with ASD: Measurement Structure and Correlates

Imitation In a Large Cohort of Preschoolers with ASD: Measurement Structure and Correlates

Saturday, May 14, 2011
Elizabeth Ballroom E-F and Lirenta Foyer Level 2 (Manchester Grand Hyatt)
9:00 AM
I. M. Smith1, C. N. Lowe-Pearce2, T. Vaillancourt3, J. Volden4, S. Georgiades5, E. Duku5, P. Szatmari5, S. E. Bryson1, E. Fombonne6, P. Mirenda7, W. Roberts8, C. Waddell9 and L. Zwaigenbaum4, (1)Dalhousie University/IWK Health Centre, Halifax, NS, Canada, (2)IWK Health Centre, Halifax, NS, Canada, (3)University of Ottawa, Ottawa, ON, Canada, (4)University of Alberta, Edmonton, AB, Canada, (5)Offord Centre for Child Studies, McMaster University, Hamilton, ON, Canada, (6)Montreal Children's Hospital, Montreal, QC, Canada, (7)University of British Columbia, Vancouver, BC, Canada, (8)University of Toronto, Toronto, ON, Canada, (9)Simon Fraser University
Background:  Children with autistic spectrum disorders (ASD) show impaired imitation of actions (Rogers & Williams, 2006). Indeed, poor elicited imitation is an early predictor of ASD in high risk infants (Zwaigenbaum et al., 2005). Most detailed investigations of imitation in ASD have used relatively small and/or selected samples, and few imitation tasks, often of 1 or 2 types (e.g., actions with objects, conventional gestures). These tasks may be insufficient to describe the growth of imitation skills in the preschool years.

Objectives:  The present study examines (1) the structure of a novel multi-dimensional elicited imitation measure, and (2) the correlates of imitative performance in a large representative sample of preschoolers with ASD.

Methods:  The study draws upon baseline data (within 4 months of diagnosis) from a longitudinal study of preschoolers with ASD (n=361; 83% males; mean age=40.8, SD=9.2 months). The Multidimensional Imitation Assessment (MIA; Lowe-Pearce & Smith, 2005) contains 48 items organized into 11 a priori domains. In this study, performance was scored in vivo on a 4-point scale for accuracy (0 = no response 1 = emerging response / not imitation; 2 = partial / inaccurate imitation; 3 = exact imitation). Age equivalent (AE) scores were used for measures of intellectual (Merrill-Palmer-Revised Scales, Developmental Index), and language abilities (Preschool Language Scales 4th ed., Auditory Comprehension and Expressive Language). Other measures were of adaptive behaviour (Vineland Scales of Adaptive Behaviour, 2nd ed, Adaptive Behaviour Composite), initiating and responding to joint attention (JA; Early Social Communication Scales) and autism symptoms (Social Responsiveness Scale Total score).

Results:  A principal components analysis (PCA) with varimax rotation on the 48 MIA item scores yielded a 3-factor solution explaining 76% of the variance. Factor 1 - Actions With Objects, accounted for 68.9% of variance; Factor 2 - Vocalizations/Words with Objects, for an additional 4.1%, and Factor 3 – Actions Without Objects, for a further 2.9%. Mean accuracy scores for each factor increased across age groups (2-, 3-, 4 –year-olds), all p’s <.001. MIA Total accuracy scores were significantly positively correlated with all ability and JA measures (r’s from .18 to .63; all p’s<.001). However, relationships with the Actions Without Objects factor appeared to be somewhat more heterogeneous, warranting further exploration. Specifically, for 2-year-olds, significant correlations were seen between both cognitive and language abilities and imitation accuracy, for both Actions With Objects and Vocalizations/Words With Objects (r’s from .20 - .50, all p’s <.02). However, for Actions Without Objects, only language scores were significantly correlated with imitation accuracy (r’s = .21 and .26, p’s <.02 and .003 for EL and AC). Relationships were non-significant between autism symptoms and all imitation factor scores.

Conclusions: The MIA provides an index of age-related improvements in multiple aspects of imitation accuracy. Furthermore, associations with measures previously linked to imitation show evidence of criterion-related validity for the MIA. We conclude that the three empirically derived factors of the MIA provide useful indices for assessing longitudinal change in imitation in preschool children with ASD. 

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