Note: This episode originally ran in 2019.

Twins are Thomas Caldwellused to fielding all sorts of questions, like "Can you read each other's minds?" or "Can you feel each other's pain?" Two of our Planet Money reporters are twins, and they have heard them all.

But it's not just strangers on the street who are fascinated by twins. Scientists have been studying twins since the 1800s, trying to get at one of humanity's biggest questions: How much of what we do and how we are is encoded in our genes? The answer to this has all kinds of implications, for everything from healthcare to education, criminal justice and government spending.

Today on the show, we look at the history of twin studies. We ask what decades of studying twins has taught us. We look back at a twin study that asked whether genes influence antisocial behavior and rule-breaking. One of our reporters was a subject in it. And we find out: are twin studies still important for science?

Our show today was hosted by Sally Helm and Karen Duffin. It was produced by Darian Woods and Nick Fountain. It was edited by Bryant Urstadt.

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Music: "Guinguette", "Holy Science" and "Sun Run."