This is Hidden Brain, I'm Shankar Vedantam.

People in romantic relationships often share things in common.

A love with the same sports team, maybe the same religion, sometimes a common profession.

But for some couples, the similarities go further.

The girl that I am dating now, we have a same birthday. This is kind of cool.

My fiance, Israel and I have the same birthday, which is something we discovered on our second date.

You could say this isn't so surprising. There are lots of people in the world, and sooner or later,

some people are going to get together with others who happen to have the same birthday.

But there's evidence this may be more than just a coincidence.

Having a common birthday seems to actually draw people closer to one another.

When I first went to a new hairstylist, we found out that we had the same birthday,

and we called each other birthday twins.

And I wound up going to that hairstylist for years, even after she switched to runs, even after we moved.

I would drive 40 minutes to go get my hair cut by her.

Some people see so much significance in shared birthdays, or even shared numbers into birthdays,

that they select dates for important events based on those patterns.

My birthday is August 2nd, and my husband, Blake's birthday is August 9th, and we got married on August 29th.

My wife and I share the same birthday to life 6th, and we are also married on that day.

My birthday is October 27th, and with my first husband, his birthday was September 27th,

and we had the opportunity to get married on August 27th. It was a no-brainer. We decided to do that.

The woman you just heard, genetic cravings from Oklahoma City, says her love for people with the same birthday, extends beyond her love life.

On October 27th is also Teddy Roosevelt birthday, and so I've always felt a little affinity for him and for his leadership.

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