Shankar Vedantam

You're listening to Hidden Brain.

I'm Shankar Vedanta.

This is Hidden Brain.

I'm Shankar Vedanta.

We've been talking with historian Stephanie Koons about how marriage changed from an institution that was primarily about economic partnerships and political expedience to one based on romantic love.

Once this shift took hold in the United States over the course of the 19th century, love marriages became the norm.

Soon, everyone wanted to know the secrets of making love last.

You've seen those documentaries and news stories about elderly couples who've managed to stay together for most of their lives.

A heartwarming documentary about the life of a couple that has been together for three quarters of a century, 75 years.

There's something that these stories don't tell you.

Social psychologist Eli Finkel at Northwestern University has studied the psychological effects of the historical changes that Stephanie has documented.

Eli is the author of The All or Nothing Marriage, How the Best Marriages Work.

He has a very dramatic term for the challenge that many couples face today.

Modern marriage, he says, runs the risk of suffocation.

To understand that term, Eli says you have to look at yet another shift that started in the 1960s and 70s.

One example of this comes from the bestselling book by Elizabeth Gilbert about walking out on her husband and trying to create a more meaningful life for herself.

We're going to play a few clips from the movies as we chat.

And this one comes from the movie Eat, Pray, Love featuring Julia Roberts.

It sounds like she was searching for her true self Eli.

This would have been unthinkable, of course, 100 years ago, let alone 500 years ago.