Timed and untimed writing and math: shared and differential cognitive predictors in primary school.

The relationship between writing and math achievement is not well understood. Phonological awareness (PA), working memory (WM), and fine motor skills (FMS) have been individually linked to theories of writing and math, yet are rarely considered together. The current study evaluates the shared cognitive factors underlying writing and math performance, both timed (e.g. fluency/automaticity) and untimed (e.g. spelling and math computation). It does so among third- through fifth-graders (n = 677) who vary in academic abilities. Results revealed differential relationships. WM had a stronger effect on writing than math for timed but not untimed outcomes. PA had a stronger effect on writing compared to math for both timed and untimed outcomes. PA also had a stronger effect on untimed math compared to timed math. Further, WM fully mediated the relationship between FMS and untimed writing but only partially mediated the relationship between FMS and other academic outcomes. Additionally, PA partially mediated the relationship between WM and all writing and math skills These findings underscore the relevance of FMS, WM, and PA in both writing and math achievement, separately and together. These findings additionally provide guidance for developing a firmer theoretical and empirical understanding of the interrelations of writing and math.