Why do we fall asleep after sex?
It's nature's way of helping us to bond and show affection for our partner, according to researchers from the University of Michigan in Ann Arbor and Albright College in Reading, Pennsylvania.
"The more one's partner was likely to fall asleep after sex, the stronger the desire for bonding," says evolutionary psychologist and lead study author Daniel Kruger, research fellow at the University of Michigan.
The study: More than 450 volunteers completed anonymous online surveys, assessing their experiences and desires for their partner after sex. Two of the questions each was asked to answer were:
- Who falls asleep after sex?
- Who falls asleep first when going to bed not after sex?
The results: Those whose partners nodded off immediately after sex had stronger desires for post-coital cuddling and chatting. Despite the common stereotype, the researchers did not find it more common for men to fall asleep first after sex.
Women, however, were more likely to fall asleep first when sex hadn't taken place. "Perhaps men stay awake longer as an artifact of mate guarding--making sure the woman doesn't leave them for another partner," says Susan Hughes, an associate professor of psychology at Albright College. "Men may also stay awake longer in an attempt to entice their partner into having sex."
Research on post-coital behaviors are limited. "The vast majority of the research on the evolutionary psychology of human reproduction focuses on what's before and leading up to sexual intercourse," says Hughes. "But reproductive strategies don't end with intercourse; they may influence specific behaviors directly following sex."
The study findings were published in the Journal of Social, Evolutionary and Cultural Psychology.
--From the Editors at Netscape