Number line estimation training in preschoolers enhances the impact of approximate numerical skills on symbolic magnitude processing

Understanding the developmental dynamics between systems supporting approximate nonsymbolic abilities and symbolic magnitude processing is key for advancing both theory and educational practice. This study examines whether a certain way of practicing number line estimation can enhance number line estimation and early math skills in preschoolers and influence the developmental dynamics 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 number line estimation practice via a game-like computerized task. Results showed significant improvements in number-line accuracy and early math skills in the experimental group, while the control group exhibited stable performance across sessions. Critically, the analysis of dynamics between symbolic and nonsymbolic abilities revealed a bidirectional relation: symbolic skills predicted nonsymbolic development across groups, but the reverse prediction from nonsymbolic to symbolic skills only emerged in the experimental group. These findings support both refinement and mapping accounts and highlight number line training as a developmental bridge between numerical systems. Implications for educational tools aiming to scaffold early numerical development are discussed.