The dynamics of fraction processing in preadolescents and adults: Evidence from reaching behavior.

Fraction processing presents an important test case for investigating the development of numerical cognition, as fraction proficiency in elementary school is a unique predictor of later mathematical achievement. Building on previous mouse-tracking research investigating the dynamics of fraction processing in adults, we used three-dimensional hand tracking to assess the dynamics of fraction processing in preadolescents (n = 30, 10-12 years of age) and young adults (n = 30, 18-22 years of age) performing a fraction magnitude comparison task. Preadolescents and adults showed limited evidence of global magnitude representations of fractions featuring congruent components and magnitudes (e.g., fractions like 1/3 and 1/4 in which the size of the components and the magnitudes of the fractions cued the same "small" response). However, clear evidence of global magnitude representations was observed on trials featuring incongruent components and magnitudes (e.g., fractions like 2/3 and 3/4 in which the size of the components cued a "small" response, but the magnitudes of the fraction cued a "large" response). The component-magnitude congruency effect observed in movement times was significantly larger in preadolescents than in adults, and the distance effect used to identify global magnitude representations was significantly larger in large magnitude fractions for preadolescents than for adults. Taken together, these results suggest that age-related changes in fraction processing reflect improved inhibitory control. More generally, our results challenge recent dual-process models of fraction processing, with performance more parsimoniously accounted for by differences in strategy rather than the involvement of distinct processes. (PsycInfo Database Record (c) 2026 APA, all rights reserved).