Nature of motor imitation problems in school-aged males with autism.

This case-comparison study explores the underlying mechanisms of imitation problems in school-aged males with autism. Analysis of congruent error types in their imitation performance was made and compared with appropriate comparisons. Fifty-five males (eight low-functioning with autism: mean age 6y 2mo [SD 7.6mo]; 13 low-functioning with learning disabilities: mean age 6y 3mo [SD 2.8mo]; 17 high-functioning with autism: mean age 8y 9mo [SD 11mo]; and 17 typically developing: mean age 8y 8mo [SD 11.6mo]) were assessed on 18 single gestures and six sequences of hand postures. Imitation performance was videotaped for blind scoring on 21 possible errors by two independent observers. Results revealed that in both groups with autism, imitation required far more effort (more attempts) than in the comparison groups and was less precise (more spatial errors). Typical for low-functioning participants with autism was their less mature imaginary grip in transitive gestures. Typical for high-functioning participants with autism was their preference for immature mirror-image imitations. These observations support the assumption that the underlying mechanisms in motor imitation problems are linked more to the action production system and less to the action conceptual system or to behavioural problems. We postulate that the action production system is delayed rather than deficient.