Trajectories and perceptual precursors of intelligence in minimally verbal autistic children from preschool to school age

Background The question of cognitive prognosis is frequently asked at the time of autism diagnosis, often at preschool age. It remains however difficult to answer this question at such a young age, given the considerable heterogeneity of cognitive development trajectories and the challenges associated with intellectual assessment in autistic children, particularly among minimally verbal children. Methods The current prospective cohort study investigated whether early perceptual abilities measured at preschool age could predict later intellectual abilities at school age in a group of 41 autistic (9 girls, 32 boys) and 57 neurotypical children (29 girls, 28 boys). Participants were assessed at three time points during the childhood period (between the age of 2 and 8 years old) using the Wechsler Preschool and Primary Scales of Intelligence – Fourth edition as a measure of full-scale IQ and the Raven’s Colored Progressive Matrices as a measure of non-verbal IQ. The performance on two perceptual tests (Visual Search and Children Embedded Figures Test) as well as the frequency of perceptual behaviors served as predictors of later intellectual abilities. Results Early performance on perceptual tests measured at preschool age was positively related to later full-scale IQ in both autistic and neurotypical children. Furthermore, both perceptual behaviors and performance on perceptual tests measured at preschool age were associated with later non-verbal IQ in the autistic group. In contrast, only the performance on Children Embedded Figures Test was associated with later non-verbal IQ in the neurotypical group. Limitations: The sample size was relatively modest, with some attrition across time points, as expected in a sample including preschool minimally and non-verbal children. Conclusions Our findings support the important role of perception in autistic cognition. Early perceptual abilities may be a valid avenue for estimating general intelligence and non-verbal abilities at preschool age, particularly for minimally verbal autistic children.