Night owls are more likely to be single or in short-term romantic relationships as compared to early birds, a new study has found.
The study suggests that sleep patterns are linked with important character traits and behaviour.
Night owls – people who tend to stay up late and wake up late in the morning – are different in many important ways from early risers, said study author Dario Maestripieri, professor in Comparative Human Development at the University of Chicago.
“Night owls, both males and females, are more likely to be single or in short-term romantic relationships versus long-term relationships, when compared to early birds,” Maestripieri said.
“In addition, male night owls reported twice as many sexual partners than male early birds,” he said.
The study, published in the journal Evolutionary Psychology, also found that women who are night owls share the same high propensity for risk-taking as men.
Researchers based their findings on data from earlier research of more than 500 graduate students at the University of Chicago Booth School of Business.
That study assessed financial risk aversion among male and female students and found men are more willing to take financial risks than women.
Females with high testosterone levels, however, were more similar to males in financial risk-taking, the study found.
Maestripieri wanted to explore why men take more risks than women.
The participants (110 males and 91 females) in the new study provided saliva samples to assess their levels of cortisol and testosterone.
They also described their own willingness to take risks and gave information about their sleep patterns.
Men had higher cortisol and testosterone levels than women; however, night-owl women had cortisol levels comparable to night-owl and early-morning men.
High cortisol levels may be a biological mechanism explaining higher risk-taking in night owls, the study suggests.
The link between the night-owl tendency and risky behaviour could have roots in evolutionary strategies for finding mates, Maestripieri said.
“From an evolutionary perspective, it has been suggested that the night-owl trait may have evolved to facilitate short-term mating, that is, sexual interactions that occur outside of committed, monogamous relationships,” he said.
“It is possible that, earlier in our evolutionary history, being active in the evening hours increased the opportunities to engage in social and mating activities, when adults were less burdened by work or child-rearing,” he added.
The findings that night owls are less likely to be in long-term relationships and that male night owls report a higher number of sexual partners offer some support to this hypothesis, Maestripieri said.