Men who are sleepy might want to second, or maybe even third-guess, whether the woman they're hitting on is actually into them, because according to a new study, sleepy men exercised poor judgment regarding how willing a woman was to have sex with them.

The effects of sleepiness were similar to those experienced when a person drinks too much. They caused men's ratings of a woman's sexual intent to rise from a score of 13.5 to 17.5, according to MedPage Today.

For the study, the researchers asked 60 college students to complete the Cross Sex Perception and Sex and Commitment Contrast psychological testing instruments before and after one night of sleep deprivation. They were then given a series of statements and asked to rate their level of agreement for each one on a scale. The statements included topics such as sexual interest, sexual intent, commitment interest, and commitment aversion for themselves, and men and women in general.

But while men showed an increase in their perceived sexual intent from women, there was no change in how the women perceived men, even with the same amount of sleep deprivation.

"Our findings here are similar to those from studies using alcohol, which similarly inhibits the frontal lobe of the brain," Dr. Jennifer Peszka, associate professor of psychology at Hendrix College, told MedPage Today.

The frontal lobe of the brain is responsible for decision making and judging the outcome of risks — sleep deprivation is known to negatively affect it, Dr. Peszka said.

"Sleep deprivation could have unexpected effects on perceptual experiences related to dating and mating that could lead people to engage in sexual decisions that they might otherwise not when well-rested," she said.

These effects could lead to a number of problems for both men and women, including sexual harassment, unplanned pregnancy, contracting sexually transmitted diseases, and relationship conflicts.

The researchers were most surprised, however, that it was only men's' frontal lobes that were impacted from sleep deprivation, and point to how women are usually looking for different things in a partner while men are just looking for sex.

"Because women are making bigger decisions that are more important to them, they may be making instinctive decisions rather than cognitive ones," Dr. Peszka said. "But this is just a hypothesis."

Regardless, it's not smart to make decisions when you are sleepy, Dr. Michael Grandner, an instructor in psychiatry at the Perelman School of Medicine at the University of Pennsylvania, told MedPage Today.

"When people are sleepy they have a lack of control in the ability to make good decisions, and this study appears to illustrate that point."


Peszka J, et al. The effects of sleep deprivation on perceptual processes involved in human mating decisions. SLEEP. 2013.