The Development of Working Memory: Sex Differences in Accuracy and Reaction Times

ABSTRACT Small but robust differences in cognition exist between the sexes in adult populations. Studying sex differences in children’s cognition can bring insight into when, where and how these differences might emerge in development. Here, we focus on differences in working memory because of its importance in underpinning a wide range of complex cognitive tasks and developmental outcomes for children. Using two levels of difficulty on a standard test of working memory (N-Back), data from 104 6- to 7-year-olds in Cuba showed that boys have quicker reaction times, but girls provide more accurate responses. With a comparable true positive rate between boys and girls, the sex differences in both accuracy and reaction times were limited to false-positive responses. Sex differences were consistent across levels of task difficulty and persisted after speed-accuracy trade-offs were considered. We argue that avoiding false positives requires a particularly strong role for inhibitory control and that this emerges in development according to a different maturational schedule for girls than it does for boys, underpinned by quantitative and qualitative differences in the development of brain areas that support this function.