June 15, 2011 -- Sleep-deprived people have trouble reading facial expressions, a new study shows, particularly when those faces are shifting away from anger or threat.
The finding suggests that sleepy people may have impaired judgment, especially in situations where they are dealing with an angry or threatening person who is backing down.
The study was presented at the annual meeting of the American Academy of Sleep Medicine and the Sleep Research Society in Minneapolis.
Tracking the Effects of Sleep on Emotional IQ
Researchers at the University of California at Berkeley scanned the brains of 12 healthy young adults as they watched a computer-generated face.
Investigators used computer software to tweak the face’s features slightly, with the lift of an eyebrow here or the flare of a nostril there, to display a gradient of emotion as it moved from either very threatening to neutral or friendly to neutral.
Study volunteers were asked to rate each of the 70 images in a series as being either threatening or nonthreatening, or friendly or not friendly.
When the participants were well rested, they had no trouble picking up on the emotional changes, but when they were deprived of sleep after 24 hours, that ability was impaired.
“As the pictures start to get less and less threatening, the people who are sleep deprived continue to rate them as threatening,” says study researcher Matthew P. Walker, PhD, director of the Sleep and Neuroimaging Laboratory and associate professor of psychology at UC Berkeley.
The ability to sense emotional shifts in friendly faces didn’t appear to be affected.
Social and Professional Consequences
“Facial expressions are probably the most salient cues that we have in our environment,” Walker says. “They profoundly influence how we behave, and they can rapidly alter your feelings and your actions toward other people.”
He says not sleeping enough could have profound social and professional consequences, particularly for people like doctors, police officers, or soldiers, who are frequently called on to quickly assess and respond to interpersonal situations.
“When you’re sleep deprived, you can’t separate threatening from non-threatening cues,” he says. “You keep thinking that they’re threatening. So you can’t accurately identify the emotion.”