There is no such thing as synchronized menstruation, but why do many women believe it is true?

Menstruation usually appears in film and television dramas for two reasons: first, tell the audience that a character's menstruation is late, thereby introducing a pregnancy story line; Second, tell the audience that the menstrual cycles of the two characters are synchronized, indicating that they are closer or have been together for a long time.

In fact, menstrual synchronization is a highly unlikely phenomenon, and there is no such thing as menstrual synchronization caused by prolonged contact in several people. However, menstrual synchronization is still a frequent topic of conversation among women in private.

In fact, menstrual synchronization is a highly unlikely phenomenon. 丨 Figureworm Creative

In part, this myth persists because many people want it to be true. No matter how inaccurate it may be, the idea that the female body can have a collective rhythm has a certain mysterious, supernatural attraction that gives the myth more inertia and provides women with a way to connect, empathize, and collectively empower other women.

There are loopholes in the study of menstrual synchronization

The concept of menstrual synchronization was first proposed in 1971 by a researcher named Martha McClintock and has gradually become known. Her study of menstrual cycle patterns, published in the journal Nature, followed 135 women's college students who lived in the same dormitory for six months and found a "significant increase in synchronization" between roommates and close friends, meaning that their menstrual start dates were less different. At the start of the study, the difference in the onset date of menstruation between friends was on average six and a half days, and towards the end of the study, the average difference was less than five days.

By 1978, McClintock's research had been cited more than 40 times in other journals and scholarly works. This data was collected by the late H. Clyde Wilson, a humanologist at the University of Missouri. Clyde Wilson Jr. suggested that he pointed out loopholes in McClintock's research in a paper published in 1992. He pointed to several methodological oversights and mentioned that while two subsequent experiments of similar design had similar findings, the other four subsequent experiments failed to replicate her results.

Studies on menstrual synchronization have been questioned a lot. 丨 Figureworm Creative

Other researchers have made further criticisms, including University of Michigan anthropologist Beverly Strassmann. In a 1999 paper published in the journal Human Reproduction, she pointed out the basic logical fallacy of the study of menstrual synchronization:

"If two women have a 28-day menstrual cycle, the maximum number of days they are out of sync is 14 days and the minimum is 0 days. In the female group, the difference in the onset of menstruation is on average 7 days, and half of the cases will be less than 7 days. Given that menstruation usually lasts 5 days, it's not surprising that menstrual periods between female friends often overlap, but this is often seen as evidence of synchronized menstruation. ”

This means that women often share menstrual periods with other women, so it's easy to mistake overlapping periods for synchronized periods, Strathman said in the interview. "Based on random probability, two women's periods overlap a quarter of the time," she said. ”

According to random probability, two women's periods overlap for a quarter of the time. 丨 Figureworm Creative

People willingly or unconsciously ignore evidence that does not support their hypotheses, and this confirmation bias can also lead to this false perception. On the other hand, because menstruation is a private matter, women rarely know how many strangers around them are menstruating at the same time. In addition, when two women are close enough to tell each other that they are menstruating, overlapping menstrual cycles can make them feel mysterious, sister-like relationships.

Strathmann believes that the rumor of menstrual synchronization has been "shattered", but because it is "a fascinating statement that goes beyond science", most people still believe it is true.

Still, women

Still believe in its existence

In 2016, Breanne Fahs, a professor of women and gender studies at Arizona State University, published research on this claim. Fass spoke to 18 women who believed they had experienced menstrual synchronization, and found several recurring themes.

Some women believe that "menstrual synchronization is due to biological factors, like animals, or by hormones." That is, it is a natural, primitive phenomenon that exists in the human body to promote the survival of the species. Other women believe that menstrual synchronization is real, but beyond what science can explain. Some women even liken it to a mysterious, invisible connection between two women.

Some women even compare menstrual synchronization to a mysterious, invisible connection between two women. 丨 Figureworm Creative

Fass also found that some women believe that when a group of female friends spend a long time together, their menstrual cycle will synchronize with a particular woman, because her "dominance" is perceived and adjusted accordingly, like a sunflower turning towards the sun. "[The idea] seems very outlandish, but it also dovetails with the way we look at social groups and social dynamics," Fass said, "and our culture does think a lot about things like dominance, hierarchy, social groups, and so on." ”

However, Fass believes her main conclusion from the study is that experiencing the pain of menstruation together satisfies the need for women to belong to the group. Women say that menstrual synchronization allows them to express anger with other women. Anger has become a platform for women to unite and make women demand higher and more determined. ”

Studies have shown that experiencing the pain of menstruation together satisfies the need for women to belong to the group. 丨 Figureworm Creative

One woman interviewed spoke lovingly about what it felt like when she started her period at the same time as her best friend, saying it was a sense of unity that "don't mess with us." Fass points out that women often face hostility or ridicule when expressing anger openly, especially as a group, so this feeling gives them a sense of power.

Another reason for the persistence of the myth of menstrual synchronization, Fass found, is that women have become accustomed to medical institutions ignoring how they feel about their bodies, that is, doctors do not value the pain and discomfort of female patients, or dismiss them as their hallucinations. Similarly, despite the skepticism of some doctors and researchers, women (and men) have believed for decades that hormonal contraceptives cause weight gain and that upcoming menstruation can cause irritability, based on first-hand experience, women's observations of their own lives, and the support of some scientists.

Pain and discomfort in women are often ignored or treated as hallucinations. 丨 Figureworm Creative

So, a few years ago, Fass presented research on women's attitudes toward menstrual synchronization at a menstrual research and advocacy conference, and when she mentioned that there was no scientific support for menstrual synchronization, there was a backlash. Other participants insisted that scientists were biased on the issue. "Women's feelings about their bodies are often overlooked," Fass said, "so people want to believe [menstrual synchronization] is real." ”

Written by Ashley Fetters

Translated by Amaranth

Editor: Li Xiaoqiu

Compiled from: https://www.theatlantic.com/family/archive/2019/09/period-syncing-almost-definitely-isnt-real/598714/