Developmental paths of the associations between visuospatial working memory and numerical processing.

The present study examines the role of spatial abilities in numerical processing in children using an application administered on parents' smartphones. The study comprised four tasks: (1) spatial short-term memory (2) spatial working memory (3) non-symbolic comparison, and (4) symbolic comparison. A total of 541 children performed all four tasks (mean age = 6.41, SD = 4.05), and a conjunction analysis was conducted on the data collected from all four tasks. One of the main goals of the present study was to understand the role of spatial abilities in numerical processing and the modulating effect of age on the relationship between them. We found that quantity comparison tasks are directly associated, primarily, with spatial short-term memory and also (but to a lesser degree) with spatial working memory. These two associations decrease with age. We suggest that younger children tend to use a spatial strategy during numerical comparison tasks. However, when symbolic and non-symbolic comparisons were combined into a unified model, no direct links were found between symbolic comparison and spatial abilities. Furthermore, in the unified model, age affected the non-symbolic comparison abilities, but not the symbolic comparison abilities. These results suggest that in young children, there is no direct link between symbolic numerical representations and spatial abilities. Accordingly, these results uniquely demonstrate that symbolic representation is built upon non-symbolic representation.