Math language matters: math-specific verbal skills, not analog representation of non-symbolic magnitudes, predict symbolic fraction abilities in primary school children.

Fractions knowledge is widely recognized as a key building block for developing mathematical competence. However, many children face difficulties learning fractions. Recognizing these challenges, researchers have sought potential leverage points to enhance children's fraction learning. In the present study, we investigated the relative contributions of verbal skills vs. non-verbal, non-symbolic number processing to 5th- to 7th- grade children's fractions skills. Specifically, we compared two math-specific verbal skills-transcoding and mathematics vocabulary-and two skills representing non-symbolic analog magnitudes-approximate number sense acuity and acuity for processing non-symbolic ratios. To assess children's symbolic fraction abilities, we used an experimental fraction arithmetic error detection task alongside a fraction magnitude comparison task, with fractions stimuli composed of two-digit components. Critically, mathematics vocabulary was the only predictor of interest that significantly predicted performance on both the error detection and comparison tasks. Our findings underscore the importance of math-specific verbal skills in supporting children's fraction abilities, perhaps implicating their role in fostering conceptual understanding, while indicating a limited role for analog representational skills.