Mental arithmetic skill development in primary school: The importance of number processing abilities and general cognitive abilities

• Grade 1 mental arithmetic relies on number abilities and cognitive abilities. • Arithmetic performance is supported by counting knowledge and number line estimation. • Arithmetic performance is predicted by logical reasoning, and spatial processing. • Arithmetic performance is predicted by phonological processing and processing speed. • Arithmetic development (grade 1 to 2) is only supported by verbal working memory. The purpose of this study was to pinpoint which mixture of cognitive abilities and number abilities underlies young children’s early mental arithmetic learning (i.e., skill development) and to examine to what extent this mixture is akin to the mixture underlying children’s early arithmetic performance. A total of 265 children were assessed on counting knowledge, symbolic magnitude comparison, number line estimation, logical reasoning, verbal working memory, spatial processing, phonological processing, and general processing speed. One year later in first grade, the children’s mental arithmetic ability was assessed, and it was then reassessed in second grade. A latent change score model showed that arithmetic performance was supported by counting knowledge, number line estimation, logical reasoning, spatial processing, phonological processing, and general processing speed, whereas arithmetic development was only supported by verbal working memory. These results demonstrate that the mixture of abilities underlying arithmetic development and arithmetic performance are rather different. Mental arithmetic performance in Grade 1 is equally dependent on a combination of both number abilities and cognitive abilities, whereas mental arithmetic development between first grade and second grade is only supported by one cognitive ability, verbal working memory.