Early development of spatial-numerical associations: consistency and variability of the SNARC effect in kindergarten children

Numbers and space are associated in the human brain. One of the most-studied spatial-numerical associations (SNAs) is the SNARC effect (Spatial Numerical Association of Response Codes), for which robust group-level effects are reported across adult studies. Despite well-replicated group-level effects, recent individual-level analysis in adults indicate that only a minority of individuals consistently map numbers onto space (Cipora et al., 2019). To date, SNARC studies in children remain generally scarce with inconclusive results. And none have explored the consistency of individual effects at earlier developmental stages. In the present study, we therefore tested 135 kindergarten children performing magnitude judgments to assess not only group-level SNARC effects but also the prevalence of individual consistency using the same methodology recently applied in adults (Cipora et al., 2019). Our findings reveal a significant magnitude SNARC effect at the group-level. However, similarly to adults, only 37% of the children consistently associated numbers with space in a left-to-right direction when considering CIs around observed effects. While these findings suggest that SNAs on average emerge earlier in life, they also point towards considerable heterogeneity across individuals in that respect. How this can help us understand the conflicting results in the literature regarding significant group-level SNARC effects in children, and guide future research on the potential relation between individual SNARC effects and educational measures in math will be discussed.