[Does the islet of ability on visuospatial tasks in children with high-functioning autism really indicate a deficit in global processing?]

Abstract

Objective: The literature on autism reports regularly the presence of a peak of ability on the visuospatial tasks. The classic interpretation of this result refers to the theoretical model proposed by Frith (1989) who evokes a "lack of central coherence" in persons with autism that is a deficit in the mobilization of global processing. The research reported here has for objective to propose a reflection on the relevance of this model by asking the following question: is global processing impaired in autism or simply not mobilized for the benefit of the almost exclusive appeal to local treatment?

Methods: A group of children with high-functioning autism was compared with normally developping children (n=15 per group), matched on age and global level of intelligence. The clinical group, 14 boys and a girl, had received a diagnosis of typical autism according to the criteria of the ICD-10 (F84.0) confirmed by ADI-R. These children all used a functional language at the time of inclusion within the study, however all of them initially presented a delay in language (mean age: 8 years and 6 months; mean total IQ: 98.07). The typically developping group, 12 boys and three girls, were from ordinary school (mean age: 9 years, mean total IQ: 106.2). Two tasks were employed for the collection of data: the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) was used to estimate the total-, verbal- and performance-IQ scores of every child and to match both groups. It also permitted the evaluation and comparison of the performances of the children on the following visuospatial tasks: "picture completion", "object assembly" and "block design". The NEPSY scale permitted the estimation and comparison of the levels of performance of both groups on visuospatial functions.

Results: In terms of scores, the tasks of the WISC-III, requiring visiospatial processing as well as the global evaluation of the visiospatial functions with the NEPSY, showed the absence of significant differences between children with high-functioning autism and typical children of the same age. However, differences of strategies appeared both between the groups and, in children with autism, according to the tasks to resolve. The comparison of subtests, "arrows" and "picture completion" on one hand, and "object assembly" and "block design" on the other, showed that children with autism are capable of mobilizing correct configural processing in the first ones but not in the second. The only factor which differentiates these tasks is the appeal or not to a motor coordination. It is possible that the lack of motor ease, often described in this type of children, sometimes leads them towards strategies of low level, i.e., to local adjustments, unlike the typical children who mobilize a strategy supported on a global representation of the purpose to be reached.

Conclusion: If our results confirm the capacities of children with autism to resolve the tasks requiring a visiospatial processing, the strategies which they mobilize do not support the existence of a weakness of the central coherence. We suggest, in persons with autism, the idea of a priority granted to the local information treatment in the absence of a deficit of global or configural processing.