• In kindergarten, numeral order is an immature skill whose performance is uniquely reliant on working memory. • By grade 4, numeral order has become an specialized skill that is no longer constrained by working memory. • Older children's math grows through both number-specific and general ordering abilities. The predictive role of numeral order knowledge for mathematics achievement is well-established but puzzlingly late-emerging, becoming a strong predictor only after the early school years. The study investigates whether this pattern reflects a developmental differentiation of the skill itself. Using a multi-cohort longitudinal design, the study followed kindergarten (n = 100) and grade 4 (n = 99) children for one year, assessing numeral and non-numeric (letter, month) order knowledge, working memory, symbolic magnitude processing, and mathematics achievement. Results showed that kindergarteners’ ability to assess the order of three numerals was an unstable, immature skill, uniquely reliant on working memory. By grade 4, it had become a specialized skill, distinct from its cognitive support. Critically, numeral order emerged as a powerful, unique predictor of mathematics growth from grade 4 to grade 5. These findings suggest the late-emerging power of numeral order knowledge is a consequence of its transformation from a resource-demanding proxy skill into a specialized, core numerical competency.
Muñez et al. (Sat,) studied this question.