Think your coworkers are secretly waiting to sabotage you? Feel like your friends are meaner than they used to be? Did your Tinder date kind of look like a serial killer in real life?
If these things are happening and you feel tired all the time, there's a good chance you're grossly misreading the emotional expressions of other people—all thanks to sleep deprivation.
A small new study published in the Journal of Neuroscience found that when people are sleep-deprived, they are more likely to perceive non-threatening individuals as threatening because their tired brains can't accurately read facial expressions. In other words, if you're tired, that coworker hanging out at your desk might suddenly come off as a menacing backstabber, and you, in turn, might treat him like one—and this could be really terrible for your life.
"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," study author Matthew Walker, a professor of psychology and neuroscience at UC Berkeley, told ScienceDaily.
For the study, Walker and his colleagues recruited 18 participants to come into their lab twice: once when they were well-rested (i.e., they'd gotten eight hours of sleep the night before) and once when they were sleep deprived (i.e., they'd been awake and monitored for 24 hours with no sleep #funtimes).
Related: Are you getting enough sleep?
During each session—sleep-deprived and not sleep-deprived—the researchers had participants look at 70 facial expressions, ranging from non-threatening to threatening. Researchers also scanned participants' brains and measured their heart rates while they rated the expressions.
As the researchers predicted, the participants who were sleep-deprived were much more likely to perceive facial expressions as threatening compared to when they were not sleep deprived. And in fact, the researchers discovered two specific areas of the brain—the anterior insula and the anterior cingulate cortex—that were not responding as they should to the shiting expressions.
"Both [these brain regions] differentiated threatening from nonthreatening facial
stimuli in the sleep-rested state," the researchers wrote in the study. "In contrast, no such discriminatory activity was observed after sleep deprivation, indicating a potential sleep-dependent deterioration of interoceptive sensitivity within homeostatic sensing networks of the brain."
Translated for non-scientists? The sensitivity of these brain regions became blunted in sleep-deprived participants, and as a result, the brain wasn't able to distinguish the emotional change properly. Not only did certain areas of the brain not respond appropriately to certain facial expressions, but the heart rates of the sleep-deprived participants were out-of-whack.
"They failed our emotional Rorschach test," Walker said. "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."
Why is this such a big deal?
The findings are pretty scary when you think about the fact that a majority of Americans are not getting enough sleep. Millions of sleep-deprived souls could be perceiving the world as a scarier, more threatening place than it may be, complaining about their coworkers or dismissing dates—making decisions based on faulty information.
"Considering the importance of accurate threat/safety-signal interpretation in determining appropriate social behaviors [these results] may further explain reported associations between reduced sleep time and increased peer-related problems in youth, decreased interpersonal functioning in adults, and antisocial interactions," argue the researchers.
They also note that the findings are especially problematic for people who work in careers where life-or-death decision-making and sleep deprivation go hand in hand—for instance, members of the military, emergency service personnel, medical professionals, and new parents.
Yet even for those of us not in high-stress careers or roles in life, this link can still pose problems. After all, most of our life is shaped by how we interact with the people around us: friends, family, bosses, lovers. If we're interacting from a place of fear, we risk creating a domino effect, in which negative interaction after negative interaction eventually leaves us in a negative state (like The Secret, but the opposite).
Moral of the story: Get some sleep!
Taryn Hillin is Fusion's love and sex writer, with a large focus on the science of relationships. She also loves dogs, Bourbon barrel-aged beers and popcorn — not necessarily in that order.