Seeing double? It’s not your imagination - birth rates of twins have been rising sharply, and twin studies are now, more than ever, influencing various disciplines. Everyone from economists, to religious scholars, to scientists see the value in studying twins. Nancy Segal, author of “Born Together-Reared Apart: The Landmark Minnesota Twin Study,” talks to us about the far-reaching effects of twins. And if you’re not a twin yourself, don’t feel left out, because what we learn from twins can lead to breakthroughs that impact us all. Segal, a professor of psychology at California State University, Fullerton, explains how twins can teach us about nature vs. nurture, parenting styles, and preventative medicine.