Night owls are more likely to be single or in short-term relationships compared to early birds.

A study involved 500 men and women who played a risk-taking game and gave saliva samples to measure their hormone levels before and after the game. They were also asked about their willingness to take risks, their relationship status, the number of sexual partners they've had, and their overall health. Some were also asked to describe themselves as a night owl, a morning person, or neither.

About 38 percent of night owl men and 37 percent of night owl women were single, while only 24 percent of early bird men and 20 percent of early bird women were single. And sleep patterns turned out to be a much stronger predictor of relationship status than risk-taking behavior or hormones.

The study defined "single" as someone who didn't have a partner or was in a relationship of six months or less, so plenty of "single" people in the study might already have been dating their soul mates. Plus, being a morning person doesn't necessarily make you luckier in love.