Scientists have long known that slumber helps make your memory sharper, can improve focus and relieve stress -- but that's not all. A new study suggests that it can also help you to appear more intelligent to others.
The way our faces look when we're tired can influence how people perceive us, and not necessarily in a good way, Sean Talamas, lead author of the study and a post-doc researcher at the University of St. Andrews in Scotland, told The Huffington Post.
"People over-generalize in judging those with droopy eyelids and a frown as being tired and having a low mood, both of which have a well-documented detrimental effect on cognitive performance," he said. "Therefore it should be no surprise that many of us find people who look less alert and who have a lower mood as less intelligent looking."
The study, which was published in the Journal of Experimental Psychology: General on Feb. 25, involved 200 participants who rated how intelligent and attractive 190 different faces, with neutral expressions, appeared in photos.
The researchers measured the degree of eyelid openness and mouth curvature seen in each photographed face, and then analyzed how the participants rated each image. They found that having more "awake" and open eyes and a slightly curved mouth related positively to intelligence ratings.
"When looking at composites of all the faces that were rated as most intelligent versus those that were less intelligent looking, subtle differences in eyelid-openness and mouth curvature continued to be prevalent in the high-intelligent looking composite images," Talamas said. "Measuring the subtlety of these differences objectively was difficult, but finding that it was related to perceived intelligence wasn't surprising."
However, the extent to which these subtle facial cues influenced perceived intelligence was astonishing, Dr. David Perrett, psychology professor at the University of St. Andrews and a co-author of the study, told HuffPost.
"We were very surprised by the size of the effects, very subtle changes in the mouth and eyes has a profound impact on impressions of ability," he said.
Perrett and Talamas agreed that the new research helps us better understand how and why we might make certain judgements of others -- especially judgments that are often stereotyped and unfounded.
"It's important to understand how we perceive others and how we are perceived, as studies show time and time again that, although frequently cautioned against it, we often judge a book by it's cover," Talamas said.
This can be particularly important in a classroom setting or job interview in which perceptions of intelligence can have a real impact," he added. "Being aware of how we can change our perceived intelligence with more sleep can hopefully encourage better sleep habits."