Sleep Deprived People Have Trouble Accurately Reading Facial Expressions

Posted on July 19, 2015

Researchers from UC Berkeley have determined that sleep deprivation makes it more difficult for people to accurately read facial expressions. The experiment involved having people view 70 different facial expressions after a full nights sleep and then after being awake for 24 consecutive hours.

The researchers note that this reduced ability to recognize expressions could have serious consequences if the sleep-deprived person does not notice a potential mugger or violent predator approaching or if a child is sick or in pain. In less serious situations it may make the sleep-deprived person more irritable if they are have trouble telling if colleagues or friends are being serious or joking.

Matthew Walker, a professor of psychology and neuroscience at UC Berkeley, says in a statement, "Recognizing the emotional expressions of someone else changes everything about whether or not you decide to interact with them, and in return, whether they interact with you. These findings are especially worrying considering that two-thirds of people in the developed nations fail to get sufficient sleep."

The 18 young adults in the experiment viewed 70 facial expressions while fully rested and in the exhausted state after being awake 24 hours. Researchers scanned participants' brains through functional Magnetic Resonance Imaging (fMRI) and measured their heart rates as they looked at the images. The findings revealed that sleep-deprived brains could not distinguish between threatening and friendly faces. The heart rates of sleep-deprived study participants also did not respond in a normal manner to threatening or friendly facial expressions. The sleep-deprived participants also interpreted more faces - even those with friendly or neutral expressions - as threatening.

Walker says, "They failed our emotional Rorschach test. Insufficient sleep removes the rose tint to our emotional world, causing an overestimation of threat. This may explain why people who report getting too little sleep are less social and more lonely."

The researchers also recorded the electrical brain activity of the participants during their full night of sleep. They found the quality of their Rapid Eye Movement (REM) correlated with their ability to accurately read facial expressions.

A research paper on the study was published here in the Journal of Neuroscience.

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