You already know that a good night's sleep and weight loss have a strong correlation, but now studies officially show that there's a connection between shuteye and perceived attractiveness. That's right: beauty sleep is real. In a scientific study published by Royal Society Open Science journal and funded by Karolinska Institutet and Stockholm University, researchers photographed 25 participants after days of both restricted and normal sleep. Then, they asked 65 women to rate the study's participants on how much they'd like to socialize with them, as well as attractiveness, health, sleepiness, and trustworthiness. The results showed that one's face can visibly convey a lack of sleep, via skin's pallor, dark circles, and droopy or swollen eyelids. Furthermore, that sleepiness can negatively affect the exhausted person's social life. When the participants were photographed after two consecutive days of just four hours of sleep a night, they were viewed as less attractive, less healthy, and less than trustworthy. According to the study, this makes sense from an evolutionary perspective. Sleepy people can look sick, and healthy individuals tend to avoid those who look ill in order to avoid contagious disease. So, the next time you miss out on a second date or invite to a party, consider: have you gotten enough beauty rest?