Are women more likely to fall asleep after sex than men? Evolutionary psychology weighs
Evolutionary psychology is known for its unique and sometimes controversial view of human behavior. Why do men prefer symmetrical facial features in women? An evolutionary psychologist might say this is because it signals “high reproductive potential.” Why are middle aged women stereotyped to be more sexually interested than younger women? Evolutionary psychology suggests that increased sexual interest should coincide with decreased fertility.
New research tackles another mind-boggling evolutionary phenomenon: why women are more likely to fall asleep after sex than men. The answer? Because it increases the chances of conception, at least according to a new article published in the journal Evolutionary behavioral sciences.
“The phrase ‘sex is nature’s sleeping pill’ is often used to capture the idea that intercourse can have sedative properties, but there hasn’t been a lot of research into this effect,” the researchers say. authors of the article, edited by Gordon Gallup of the University. at Albany, State University of New York. “We found that women were more likely than men to report falling asleep after sex and that post-lovemaking sleepiness was enhanced by orgasm in both women and men.”
While this conclusion may seem counterintuitive, here’s a step-by-step look at the logic behind it:
- Humans have developed upright posture and bipedal movement as a means of optimally navigating their environment.
- One of the disadvantages of an upright posture is that it places the female reproductive system in an orientation perpendicular to gravity.
- It is not ideal for retaining sperm and, by extension, maximizing the chances of conception during sex.
- To overcome this problem, evolutionary psychologists point out that the “missionary position” has become an intercultural universal.
- But they argue that there is another mechanism by which evolution has stacked the game in favor of design: by imbuing seminal fluid with sedative properties. This encourages women to stay lying down after sex, which helps retain more sperm in the female reproductive system and further increases the chances of conception.
To test their reasoning, the researchers recruited 316 undergraduates from the University of Albany to participate in a short survey of sexual routines. They excluded people who indicated a bisexual or homosexual preference or who did not report any previous sexual experience. They also excluded participants who reported having more sex during the day than at night since the aim of the study was to understand post-coital sleep routines. This resulted in a final sample of 128 women and 98 men.
Participants were asked to complete a survey consisting of three sections: contraceptive use and relationship status, masturbatory behavior, and history of sexual intercourse. Participants’ responses to the following three questions were critical to their investigation:
- Who usually falls asleep sooner after penile-vaginal sex, you or your partner?
- How often do you fall asleep after having an orgasm during penile-vaginal sex?
- How often do you fall asleep after vaginal sex without having an orgasm?
It’s no surprise that men and women fall asleep faster after sex when they have an orgasm. However, with or without orgasm, women were more likely than men to fall asleep sooner after sex.
The discovery that there was no gender difference in the sedative properties of masturbation was crucial to their hypothesis. It was only when women were inseminated that they reported a greater likelihood of falling asleep after sex. This reinforces the argument that seminal fluid may contain sedative-like properties.
This study is not without limits. On the one hand, the sample size is relatively small and the data is correlational and not causal. In fact, the correlational nature of the study points to a broader critique of the field of evolutionary psychology, namely that many of its theories are virtually unverifiable (at least in the traditional sense).
Having said that, most scientists know better than to bet against evolutionary theories.