Number-line estimation training in preschoolers supports early mathematical development and is associated with a...

Understanding how children connect approximate nonsymbolic magnitudes with exact symbolic numbers is a central question in theories of numerical development. A major debate concerns the directionality of this relation: whether approximate magnitude representations scaffold the acquisition of symbolic number knowledge, as proposed by mapping accounts, or whether symbolic number learning refines approximate magnitude processing, as proposed by refinement accounts. This study examined whether number-line estimation training enhances preschoolers' number-line accuracy and early mathematical abilities, and whether it is associated with short-term developmental pathways between nonsymbolic and symbolic numerical systems. A total of 114 Swedish preschoolers participated in a pre-post intervention study, with an experimental group receiving three sessions of game-like computerized number-line estimation practice on a bounded 0-20 number line with trial-by-trial feedback. Results showed a large improvement in number-line accuracy and a modest but significant transfer effect to early mathematical abilities in the experimental group, whereas the control group showed no comparable gains in these intervention outcomes. Analyses of symbolic and nonsymbolic numerical processing revealed two complementary predictive dynamics. Symbolic abilities predicted later nonsymbolic performance after controlling for baseline nonsymbolic performance and condition, consistent with the refinement account. Conversely, nonsymbolic abilities predicted later symbolic performance after controlling for baseline symbolic performance and condition, consistent with predictions from the mapping account. Importantly, post-hoc analyses yielded converging, moderate directional evidence that this approximate-to-symbolic predictive relation was stronger in the experimental group than in the control group, consistent with the possibility that number-line training supports the coordination of approximate and symbolic numerical representations. These findings are consistent with a bidirectional view of numerical development in which symbolic knowledge refines approximate magnitude processing, while approximate numerical abilities can support symbolic development when children engage in learning activities that bridge both systems. By positioning number-line estimation as both an educational tool and a bridge between numerical systems, this study may help clarify mixed findings on developmental directionality and highlights a brief, scalable activity for scaffolding early mathematical learning.