The Temple professor initially believed that early puberty caused conflict between girls and their parents. Then he was “blown away” when his research showed the reverse connection: family conflict led to early maturation.

Question: Have you done research where the result turned out differently than you expected?

Laurence Steinberg: Well, I can think of two things, okay? One was very early in my career, and one was more recently. The early one was the following: I had done my doctoral dissertation on how family relationships change when kids move from childhood into adolescence. And what we found was that as a direct function of pubertal maturation, there was an increase in conflict between kids and their parents. And I was writing -- this is now back in the late '70s -- about why puberty caused conflict between kids and their parents. And about 10 years later I was driving around with a friend of mine, another psychologist, and he said, have you ever thought about maybe it's the other way around? Maybe family conflict causes kids to go through puberty. And I thought, wow, that's a wild idea!

And we had these data where we had followed people over time, where we had measured puberty and family conflict and different points in time, so we could look at kind of which came first. And sure enough, we found that kids who grew up -- now, this was limited to girls -- that girls who grew up in family environments characterized by higher levels of conflict went through puberty earlier, which was -- it just completely blew me away. And when I first presented this -- I remember I was out at Stanford giving a talk, and a very famous psychologist there, Eleanor Maccoby, came up to me afterwards, and she said, that was a beautiful talk, but I don't believe any of it. And you know, this was the first study in humans to demonstrate this. Now, we know that biological functioning is influenced by social factors. There's the whole thing of menstrual synchrony: when women live together their menstrual periods tend to get synchronized, and so on. But nobody had shown this before. And since then it's now been replicated in a bunch of different studies, and it's kind of an accepted fact within developmental psychology. So that was something that really surprised me, that I would never have predicted.