Chicks Don’t Synch

Another myth we need to stop spreading: Women who live together eventually have their menstrual cycles synch up.

Of course they don’t! Think about it. Have you ever lived with even two women who were perfectly aligned? If this myth were true, wouldn’t we all have at least one instance of witnessing this happen?

I’d be happy if the people I lived with would just adapt the same sleeping cycles!

So why do we all believe it’s true? Because a scientist told us so, and in these enlightened days we rarely stop to run published scientific papers through the bullshit-ometer.

The woman who started all this, Martha McClintock, was getting her degree from Wellesley College in 1970 and, being trapped in an all-women’s school, she probably spent half her time chatting about menstrual cycles and decided it would make a fascinating study. It went well, got published, led to national attention … go, Martha, right? But as with most college papers you remember doing, it was a bit of a rush job.

She took a very small sample group (135 women) over a very short time period (a few months), had them self-report the statistics, and … well, some of the women started to get closer together. Groovy, but when you remember that a typical woman’s cycle is anywhere from 21-35 days apart, of course some of the start dates between women would be getting nearer. Then again, if she’d studied over a few years, she’d have seen those same specific women drift apart again.

Why? Because her central thesis was flawed – women may overlap with those they live with, but one woman’s periods have no effect on another’s. Truly. None whatsoever.

Whereas numbers don’t lie, statistics nearly always do.

Never trust an over-eager grad student rushing to publish.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

Blog at

Up ↑

%d bloggers like this: