Is children's daily working memory performance related to their sleep?

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Recent studies have suggested that adults' cognitive performance fluctuates substantially both between and within days, but little is known about such fluctuations in children. Children's sleep behavior might influence their daily cognitive resources, yet naturally occurring variations within individual children had not been studied in their everyday lives.

In an ambulatory assessment study, 110 elementary school children aged 8–11 completed sleep items and working memory tasks on smartphones several times a day, at school and at home, for 4 weeks. Parents provided general information about the children and their sleep habits.

The researchers found substantial fluctuations in the children's daily cognitive performance, self-reported nightly sleep quality, time in bed, and daytime tiredness. All three sleep-related facets predicted performance fluctuations in children's school and daily life. Sleep quality and time in bed predicted morning performance, while afternoon performance was related to current tiredness. Children with lower average performance showed a stronger within-person coupling between morning performance and sleep quality.

The findings offer insight into a potential source of performance fluctuations in children. The researchers said the effects of varying cognitive resources need further investigation because they might affect children's daily social, emotional, and learning-related functioning. They also suggested that theories of children's cognitive and educational development should consider fluctuations on micro-longitudinal scales, such as day-to-day changes, to identify possible mechanisms behind long-term changes.