Developmental trajectories of symbolic magnitude and order processing and their relation with arithmetic development

Efficient processing of absolute magnitude and relative order of numbers is key for arithmetic development. This longitudinal study tested 1) whether there is a developmental shift in the contribution of symbolic magnitude and order processing to arithmetic between Grades 1 and 2, and 2) whether the development of symbolic numerical abilities is characterized by reciprocal predictive relations. In two independent samples (UK: N = 195, Austria: N = 161), order processing did not predict early developmental change in arithmetic, but emerged as a predictor in Grade 2. Symbolic magnitude processing in Grade 1 predicted subsequent developmental change in arithmetic, but not later on. Moreover, we observed cross-lagged relations between symbolic magnitude and order processing. Our findings confirm that the contributions of symbolic magnitude and order processing to arithmetic development are interactive and change across the first years of schooling. This may be driven by a developmental shift from procedural strategies to retrieval of arithmetic facts.