We know all about how facial expressions can make a difference in social interactions. Need we say more than, "RBF?" But a new study suggests that when children are overtired, their facial expressions can predict their propensity for having social problems, even years later.

The study, published in Affective Science by University of Houston professor of psychology Candice Alfano, looked at how changes in children's facial expressions when they're overtired or been deprived of sleep could predict their propensity toward social problems--then or on the future.

Dr. Alfano said, "Sleep problems in children are routinely linked with lower social competence and more problems in peer relationships, but we really don't understand what drives these associations."

She hypothesized that some of that may lie in the ways that children's faces presented emotions when they were tired.

For her study, she and colleagues looked at 37 children between the ages of 7 and 11 during two in-lab emotional assessments. One was when the children were well-rested and another was after two nights of partial sleep restriction. In the assessments, children looked at positive and negative pictures. Positive pictures included things like sweets and baby animals while negatives included things like scary dogs and getting shots. The parents of the children shared reports of the children's social functioning then and two years after the showing.

Dr. Alfano said that as suspected, the kids who showed fewer positive facial expressions in response to the pleasant images when they were tired also were reported to have more social problems two years later.

Alfano said that concurrent relationships between sleep-based changes and their expressions and social problems weren't necessarily found but that may be due to developmental differences in peer relationships and social behavior.

She said younger children had more explicit behaviors that showed importance in friendships--like taking turns and sharing. But as kids age, their subtle facial expressions provide not just how one is feeling, but can even have a contagion effect on how others around you feel.

This study supports other research that shows poor sleep habits and quality in childhood can indicate socio-emotional problems later in life but also shows how important it is for sleep in children's mental health and well-being. While this can come off as discouraging for some, it's actually great advocacy of attachment parenting sleeping practices so that mama and baby are as well-rested as they can be.

Image: MaLija/Shutterstock