Surveys reveal why partners fall asleep after sex

Kathleen Blanchard's picture
Falling asleep after sex comes from a desire to bond, finds online surveys.

Scientists are finally trying to figure out what it is that makes a partner fall asleep after having sex. Researchers at the University of Michigan and Albright College in Pennsylvania found sleeping after sex stems from a desire for bonding and affection.

Partners who reported a stronger desire for long-term commitment were more likely to fall asleep after having sex. The finding suggests The Post-Coital Time Interval (PCTI), or behavior following sex, may be important for establishing a committed relationship, according to the authors.

The study found women were more likely to fall asleep before men when going to bed without having sex. However, there was no difference between men and women and sleep onset after sexual intercourse.


The researchers say there hasn’t been much attention paid to reproductive strategies after having sex, though much has been studied about mate selection and differences between genders. For instance, women are more selective than men when it comes to choosing a partner. Men have a desire for more sexual partners and are less likely to desire monogamy.

The study authors say, “Falling asleep before one’s partner may be a non-conscious mechanism that forecloses on any commitment conversation occurring after sexual intercourse. If men actively avoid commitment promises in post-coital conversation, this could increase the likelihood of women ending the relationship due to perceptions of undesirable partner characteristics and/or uncertainty about the future of the relationship. Hastening sleep onset may evade this adverse effect.”

The results were taken from online anonymous surveys from 456 participants. Daniel Kruger, research fellow at the University of Michigan, and lead author of the study says the finding shows falling asleep first after sex comes from a strong desire for bonding.

Journal of Social, Evolutionary, and Cultural Psychology
2011, 5(4), 239-247.
"Tendencies to Fall Asleep First After Sex are Associated with Greater Partner Desires for Bonding and Affection"
Daniel J. Kruger, Susan M. Hughes

Image credit: Bing


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