Sleep Deprivation Limits Our Ability to Read Certain Facial Expressions

Fagjun | Published 2017-03-27 19:52

How well can you identify the emotions in these faces?
[Illustrations by Charles Lebrun]

Scientists have found that sleep deprivation makes us unable to read emotions like happiness and sadness on people's faces. However, we are still able to read primitive emotions like fear, anger, or surprise.

There may be an evolutionary reason behind this. According to the study, when we are tired, some of our survival instincts kick in. Emotions like fear and anger may indicate a threat, so we instinctively pay less attention to “harmless” emotions. This way, we can focus more on emotions that may affect our short-term safety.

"If someone is going to hurt you, even when you're sleep deprived you should still be able to pick up on that," says researcher William D.S. Killgore. Our brains instinctively tune into emotions that may spark aggression. Harmless social emotions do not warrant as much recognition when we are tired as primitive emotions do.

Sleep Deprivation and Survival

54 volunteers participated in the research. The researchers showed them images of the same man expressing degrees of emotions like fear, anger, disgust, and surprise. The participants then had to identify which image expressed the highest degree of those emotions.

Researchers also asked participants to read “composite” emotions by showing images of faces that show two emotions like sadness and disgust. The participants were able to identify 180 blended emotions in each session.

The participants were then asked to get little sleep in preparation for the next round of tests so researchers can test the effects of sleep deprivation.

The tests showed that participants suffering from sleep deprivation were still able to read different emotions, albeit only when blatant. This time, however, participants were unable to identify sadness and happiness in subtler forms. Interestingly, they were still able to identify primitive emotions regardless of how subtle these emotions were.

After just one night of sleeping soundly, the participants were again able to identify both social and primitive emotions.

Social Impact

Sleep deprivation can thus affect various social interactions. "You may be responding inappropriately to somebody that you just don't read correctly, especially those social emotions that make us human,” says Killgore. We may end up with less empathy, but it's not because there's something fundamentally wrong with us. It's mostly because when we lack sleep, we have an impaired ability to identify emotions we should empathize with in the first place.

Regardless, this can lead to problems at home, work, school, and within personal relationships. Thus, sleep deprivation doesn't just make us sleepy and tired all day. It can also impact our social interactions. We're also merely surviving when we lack sleep; we're not thriving.

We all know sleep deprivation sucks. Now, though, we know how and why.

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