Number line knowledge is widely recognized as a strong predictor of children’s math achievement. In this longitudinal study, we investigated the interplay between domain-general (i.e., visuospatial working memory) and domain specific indicators (i.e., verbal counting, one-to-one counting) of number line knowledge in children attending the second and third year of preschool. A total of 135 children underwent assessments in two phases (T1 and T2), five months apart. At T1 children were tested on visuospatial WM, verbal counting, one-to-one counting, and number line knowledge. At T2, the evaluation of number line knowledge was repeated. Path analysis revealed that children’s visuospatial WM predicted number line knowledge at T2, both directly and indirectly through the mediators of verbal counting and number line knowledge at T1. Findings suggest visuospatial WM is essential for acquiring number line knowledge and that verbal counting may serve as a strategy for estimating number positions in number line tasks. The implications of these findings for early math education in preschool settings are discussed.
