Number Sense In Autism

Background: Number skills are often reported anecdotally and in the mass media as a relative strength for individuals with an autism spectrum condition. Yet the few existing studies on arithmetic ability using standardized assessments suggest that these skills are in fact extremely heterogeneous. As informative as these standardized tests are, they are unable to provide a detailed and comprehensive analysis of why such achievement is so variable in autism. Here we investigate autistic children's so-called "number sense" - their intuitive understanding of numerical magnitude - to determine whether individual differences in this sense are a potential source of the variability in these children's formal arithmetic skills.

Objectives:  The objectives of this study were threefold: (1) to compare numerosity performance in groups of school-age children with and without autism of similar age, gender, and ability using a child-friendly and developmentally-sensitive psychophysical task; (2) to determine whether children with autism, like typical children, are able to translate between symbolic representations and spatial representations of number using the "number line", another potential source of individual differences in arithmetic achievement; and (3) to establish whether individual differences in these skills are related to differences in mathematical achievement within each group.

Methods:  In an ongoing study, eight children with autism aged between 8 and 12 years, and 15 typically developing children, of similar age and nonverbal ability, were administered two experimental estimation tasks: one psychophysical non-symbolic estimation task, which asked children to make simple more/less judgments, and one symbolic estimation task, which asked children to estimate the location of numbers on a number line. Mathematical achievement and general cognitive abilities were measured with standardized tests.

Results:  Group-based analyses revealed that children with autism performed significantly worse than typical children on the standardized measure of arithmetic skills. More crucially, children with autism also performed poorly on both experimental tasks relative to typical children, showing difficulties estimating numerical magnitude and matching spatial quantities with a numerical value. Furthermore, individual differences in estimation were significantly correlated with children's mathematical scores in both groups of children.

Conclusions:  Contrary to widespread opinion that mathematical skills are generally enhanced in autism, these initial findings suggest that children with autism show poorer mathematical achievement relative to typical children of similar age and ability, and importantly, that individual differences in such achievement might be due to fundamental difficulties in autistic children's number sense.