Overlap between reading and arithmetic skills from primary to lower secondary school and the underlying cognitive mechanisms

Reading and math skills are fundamental for school achievement, and these two basic academic skills have been shown to be strongly related. However, there is a lack of knowledge regarding the longitudinal relationship between reading and arithmetic skills, as well as on the underlying cognitive mechanisms. Investigating the overlap (i.e., shared variance) between reading and arithmetic skills across grade levels can provide valuable information about the development of these skills in relation to each other, which is important in understanding the comorbidity of learning difficulties and in designing more effective interventions. This research aimed to complement the current understanding of the overlap between reading and arithmetic skills with three separate studies. In Study I, an unselected population was used to investigate the extent to which reading and arithmetic skills show overlap in Grades 1 and 7, and the extent to which this overlap is time-invariant, on the one hand, and time-specific, on the other. Furthermore, the study investigated the extent to which different cognitive antecedents, along with parental education, predict the time-invariant and time-specific parts of the overlap. In Study II, a person-oriented approach was applied to complement the variable-oriented research by investigating individual differences in cognitive profiles composed of shared predictors of reading and arithmetic skills. In addition, the relations of these profiles to subsequent reading and arithmetic skills and to the overlap between these skills during primary and lower secondary school were investigated. Finally, Study III focused on the association of prematurity with the overlapping part of reading and arithmetic skills at the beginning of school and the cognitive antecedents explaining this association. Overall, the results revealed that reading and arithmetic skills show substantial overlap across grade levels from primary to lower secondary school, which is predicted mainly by linguistic and basic number skills related to developing fluency in these two domains (Study I). The results showed further that individual variations in patterns of performance exist across linguistic and basic number skills that differentially predict the overlap of subsequent reading and arithmetic skills (Study II). Finally, the results showed that prematurity was negatively associated with the overlapping part of reading and arithmetic skills rather than the unique variation of these skills, and this association was due to the premature children’s weaknesses in cognitive antecedents predicting the overlap between reading and arithmetic skills (Study III). In general, the results suggested that reading and arithmetic skills develop in tandem among most of the children due to the partly shared cognitive background; thus, children with difficulties in one domain should be closely monitored for difficulties in the other domain as well.