Science has proven that there’s actually a thing like waking up on the wrong side of the bed and not understanding your partner.
After a rough night’s sleep, your ability to recognise whether those around you are happy or sad could suffer, according to a study led by a University of Arizona psychologist.
The research, published in the journal Neurobiology of Sleep and Circadian Rhythms, found that study participants had a harder time identifying facial expressions of happiness or sadness when they were sleep deprived versus well-rested.
The sleepy participants’ ability to interpret facial expressions of other emotions — anger, fear, surprise and disgust — was not impaired, however. That’s likely because we’re wired to recognize those more primitive emotions in order to survive acute dangers, said lead researcher William D.S. Killgore, a UA professor of psychiatry, psychology and medical imaging.
While emotions such as fear and anger could indicate a threat, social emotions such as happiness and sadness are less necessary for us to recognize for immediate survival. When we’re tired, it seems we’re more likely to dedicate our resources to recognizing those emotions that could impact our short-term safety and well-being, Killgore said.
“If someone is going to hurt you, even when you’re sleep deprived you should still be able to pick up on that,” Killgore said. “Reading whether somebody is sad or not is really not that important in that acute danger situation, so if anything is going to start to degrade with lack of sleep it might be the ability to recognize those social emotions.”
The data used in the study was part of a larger research effort on sleep deprivation’s effects on social, emotional and moral judgment. Killgore began the project while working as a research psychologist for the U.S. Army.
Researchers found that blatant facial expressions — such as an obvious grin or frown (90 percent happy or 90 percent sad) — were easily identifiable regardless of how much sleep a participant got. Sleep deprived participants had a harder time, however, correctly identifying more subtle expressions of happiness and sadness, although their performance on the other emotions was unchanged.
When participants were tested again after one night of recovery sleep, their performance on happiness and sadness improved, returning to its baseline level.
“So, in simplistic terms, the part of the brain that controls your emotions and the part that sees faces and responds to the emotional content basically start to lose their ability to communicate,” Killgore said. “We wanted to test that out and see if it plays out in terms of how people read facial expressions — and, in fact, it looks like it does.”