# Why do women's periods syncronize? **URL:** \ **Category:** Factual Questions\ **Created:** [November 7, 2006, 4:05pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437 "2006-11-07T16:05:42Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![DooWahDiddy](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@DooWahDiddy](https://boards.straightdope.com/u/DooWahDiddy)\ **Post date:** [November 7, 2006, 4:05pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/1 "2006-11-07T16:05:42Z")
As a man, I’m constantly amazed and confused by the female body. One of the things that totally blows my mind is the phenomenon that makes women’s periods syncronize when they live together. What’s happening here? What _is_ it that’s connecting them? I’ve also heard that if one of the girls is on the pill, then the other girl(s) will adapt to her period, not the other way around. So what if nobody’s on the pill? How is it decided who to sync up to? And do the girls have to live in the same room, or the same house in separate rooms, or what? What’s the maximum footage/yardage/mileage they can live apart and still have this happen? How long do you have to know a girl before it starts, or do you have to know them at all? Is it possible to be syncronized with someone and not know it? And finally, where did this evolve from? What good does it do for humans that it has stuck around thousands of years? It’s actually quite impressive… kind of like a hidden superpower or something (“Ladies, sync up!”) but I’d really like to know the reasoning behind it all. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 7, 2006, 4:11pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/2 "2006-11-07T16:11:47Z")
You can read up on the Master’s answer here: [Do the menstrual cycles of women living together tend to synchronize?](http://www.straightdope.com/classics/a2_306.html) ---
**Author:** ![outlierrn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/outlierrn/32/3005_2.png) [@outlierrn](https://boards.straightdope.com/u/outlierrn)\ **Post date:** [November 7, 2006, 4:28pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/3 "2006-11-07T16:28:41Z")
[http://www.straightdope.com/columns/021220.html](http://www.straightdope.com/columns/021220.html) be sure to read the updated column as well ---
**Author:** ![Mr\_Feldman](https://avatars.discourse-cdn.com/v4/letter/m/71c47a/32.png) [@Mr\_Feldman](https://boards.straightdope.com/u/Mr_Feldman)\ **Post date:** [November 7, 2006, 4:36pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/4 "2006-11-07T16:36:28Z")
Its quite common for the more dominant woman to control the cycle for the other women. This is why it is very important not to be in the house when they all have their periods at the same time. Take up camping, fishing, anything that will help keep you out of the house for a minimum of 5 days ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [November 7, 2006, 4:39pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/5 "2006-11-07T16:39:50Z")
as I’ve mentioned in previous discussions on this topic, Pepper Mill is in no doubt that menstrual synchronization is a real phenomenon. Until they started regulating her cycle with medication, she had _extremely_ irregular cycles. Worse, she weas the “alpha female” in her social group, at least as far as dictating everyone else’s cycle – they all ended up with irregular cycles that matched hers. That’d be a hard effect to explain via statistical probability, since it wasn’t only the fact that they were falling ion line with her menses, but that the periods weren’t of regular length. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [November 7, 2006, 4:58pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/6 "2006-11-07T16:58:05Z")
Is there a way to predict who is the “alpha female” w/r/t synchronization? Age, status, size, etc.? Or are there no parameters they have found yet? ---
**Author:** ![DooWahDiddy](https://avatars.discourse-cdn.com/v4/letter/d/e9bcb4/32.png) [@DooWahDiddy](https://boards.straightdope.com/u/DooWahDiddy)\ **Post date:** [November 7, 2006, 5:10pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/7 "2006-11-07T17:10:42Z")
Thanks for the responses so far! I guess I also need to buy a dictionary and learn how to spell “synchronize”. :rolleyes: ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [November 7, 2006, 6:05pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/8 "2006-11-07T18:05:26Z")
[QUOTE=Mr Feldman] Its quite common for the more dominant woman to control the cycle for the other women. [/QUOTE] Oh, and dont forget about what happens when there is a full moon on the day they all synch. Then they act _extra_ crazy. :rolleyes: ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [November 7, 2006, 6:10pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/9 "2006-11-07T18:10:34Z")
[QUOTE=CalMeacham] as I’ve mentioned in previous discussions on this topic, Pepper Mill is in no doubt that menstrual synchronization is a real phenomenon. Until they started regulating her cycle with medication, she had _extremely_ irregular cycles. Worse, she weas the “alpha female” in her social group, at least as far as dictating everyone else’s cycle – they all ended up with irregular cycles that matched hers. That’d be a hard effect to explain via statistical probability, since it wasn’t only the fact that they were falling ion line with her menses, but that the periods weren’t of regular length. [/QUOTE] Statistical probability might not _have_ to explain anything. Have they ever kept a menstrual log? Did it include several months prior to meeting and several more after becoming friends and synched? If so, I’d like to see the data. If not, I think it’s just a bunch of girls talking and creating there own evidence. Like “Ohhhh yeahhhhh. Last month we started on the same day toooo. OMG, it’s soooo strange.” ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [November 7, 2006, 6:26pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/10 "2006-11-07T18:26:49Z")
> [@](#): > > Statistical probability might not have to explain anything. Have they ever kept a menstrual log? Did it include several months prior to meeting and several more after becoming friends and synched? If so, I’d like to see the data. If not, I think it’s just a bunch of girls talking and creating there own evidence. Like “Ohhhh yeahhhhh. Last month we started on the same day toooo. OMG, it’s soooo strange.” Well, since I’m not female, and this happened before Pepper met me, no, I didn’t keep the logs. BUT, considering that there were bitter recriminations over many misplaced periods, it’s more than a case of a"bunch of girls talking and creating their own evidence". Sometimes observations do get masde over anomalies, and it’s that kind of thing that often results in more careful experimentation being made. Pepper went to the doctor with this observation, and it was taken seriously enough to get her put on meds. Yeah, I know that anecdotal evidence s untrustworthy, and people’s perceptions can color thingfs. But it doesn’t always happen. Sometiomes observations are accurate. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [November 7, 2006, 8:26pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/11 "2006-11-07T20:26:43Z")
Just to make sure that [Cecil’s updated column](http://www.straightdope.com/columns/021220.html) from 2002 gets a link–and in that column, Cecil says the scientific evidence is leaning against sychrony. ---
**Author:** ![jellyblue](https://avatars.discourse-cdn.com/v4/letter/j/e480ec/32.png) [@jellyblue](https://boards.straightdope.com/u/jellyblue)\ **Post date:** [November 8, 2006, 12:43am UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/12 "2006-11-08T00:43:49Z")
I’m gay and have been living with my partner for a year and a half. We get our periods at different times. Same was true with my ex and I was with her 7 years. Must be something about straight girls 😃 . Men, maybe? :eek: ---
**Author:** ![The\_Flying\_Dutchman](https://avatars.discourse-cdn.com/v4/letter/t/9fc348/32.png) [@The\_Flying\_Dutchman](https://boards.straightdope.com/u/The_Flying_Dutchman)\ **Post date:** [November 8, 2006, 2:18am UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/13 "2006-11-08T02:18:46Z")
[QUOTE=jellyblue] I’m gay and have been living with my partner for a year and a half. We get our periods at different times. [/QUOTE] The words I hate to hear. “Sorry hun, not tonight, I just started my period.” Damn! My sympathies. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [November 8, 2006, 2:57am UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/14 "2006-11-08T02:57:07Z")
[QUOTE=jellyblue] I’m gay and have been living with my partner for a year and a half. We get our periods at different times. Same was true with my ex and I was with her 7 years. Must be something about straight girls 😃 . Men, maybe? :eek: [/QUOTE] Actually, the fact that gay women do not report sychronisation is specifically mentioned in Cecil’s updated column. It seems to me there are (at least) two possibilities. One is that for some reason gay women don’t synch when straight women do. However, as the column notes, nuns reportedly synch, so if that’s right, men can’t be the cause. The second possibility is that the whole synching thing is horsehockey and that straight women (who only talk about it) have sufficient room for memory error etc to believe the theory, while gay women who are intimate enough to _know_ to the precise day when their partner’s period starts, give more accurate and less supportive data. ---
**Author:** ![outlierrn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/outlierrn/32/3005_2.png) [@outlierrn](https://boards.straightdope.com/u/outlierrn)\ **Post date:** [November 8, 2006, 3:23am UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/15 "2006-11-08T03:23:33Z")
Is nobody reading the updated article??? It’s been linked to twice ---
**Author:** ![jellyblue](https://avatars.discourse-cdn.com/v4/letter/j/e480ec/32.png) [@jellyblue](https://boards.straightdope.com/u/jellyblue)\ **Post date:** [November 8, 2006, 4:05am UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/16 "2006-11-08T04:05:19Z")
[QUOTE=The Flying Dutchman] The words I hate to hear. “Sorry hun, not tonight, I just started my period.” Damn! My sympathies. [/QUOTE] Oh, no sympathies needed - we’re creative 😃 . ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [November 8, 2006, 7:11pm UTC](https://boards.straightdope.com/t/why-do-womens-periods-syncronize/379437/17 "2006-11-08T19:11:22Z")
[QUOTE=CalMeacham] Sometimes observations do get masde over anomalies, and it’s that kind of thing that often results in more careful experimentation being made. Pepper went to the doctor with this observation, and it was taken seriously enough to get her put on meds. [/QUOTE] Are you saying she was put on meds to prevent her from influencing her friends’ periods? > [@](#): > > Sometimes observations do get masde over anomalies, and it’s that kind of thing that often results in more careful experimentation being made. Yeah, but after doing more careful experimentation or documentation, people realize there’s really no connection. There’s a thread about people acting crazy because of the moon. Many Emergency Service people will swear this is true and that it _always happens_. There’s an ER worker who decided to actually record data and realized that the occurrances of whackjobs was just as random on Full Moons as any other night. They just noticed them more on fullmoon nights and applied a correlation where none existed. I’m confident that if ever a group of friends actually recorded their periods, they’d notice there’s nothing special going on. I’d really like to see a group of close friends and a group of controls (who dont know each other) all record their periods for like 2 years, and then have that data compiled by a person who doesn’t know which girls are which. I’m confident we’d see that group interaction has no effect on menstrual cycles. If there were some girls who were always very regular, but became irregular when they started working with some irregular Alpha Female. My first hypothesis would be that the environment (stressful job) was the common factor effecting the periods, and not some pheromone or something emitted by the dominant bitch.