Individual differences in processing speed mediate a relationship between working memory and children's classroom behaviour

• Working memory is thought to relate to measures of attention in the classroom.
• We replicate this association in an unselected sample of 6- to 8-year-olds.
• We successfully decompose working memory into its component functions.
• Differences in processing speed account for the relation with classroom behaviour.
• Speed, rather than memory, may be the crucial determinant of classroom attention.

Previous studies have shown an association between children's working memory performance and teacher ratings of classroom inattention, leading to the suggestion that children who appear inattentive may in fact suffer from reduced working memory capacity. However, working memory performance is determined by a range of factors and in this study we examine the relationships between the teacher ratings of classroom behaviour and the various constraints on working memory performance in a representative sample of 6- to 8-year-olds in mainstream education. Analysis of individual differences confirmed that working memory scores could be decomposed into the following components: storage capacity, processing efficiency, and the residual variance that results from combining storage and processing operations. However, only processing efficiency was reliably related to teacher ratings of individuals' ability to concentrate and learn in the classroom, suggesting that individual differences in basic speed of processing, rather than in memory capacity, drive this relationship.