A lot can be learned from scientific twin studies about the relative contributions of nature versus nurture to human experience. However, when such studies do lasting harm to its participants, what does it teach us about the dangerous power of scientific zeal? This is the subject of Dr. Nancy Segal’s latest book, Deliberately Divided: Inside the Controversial Study of Twins and Triplets Adopted Apart (Rowman & Littlefield, 2021), in which she documents the controversial methods employed by the Louise Wise Services-Child Development Center Twin Study of the 1960s and 1970s. In our interview, she addresses the fallout of such methods for twins that were studied but kept unaware of each other for years and what it says about the unique bond shared by twins. This discussion of a tragic but fascinating and important moment in scientific history is relevant for anyone interested in questions about the roles of genes versus the environment or about the uniqueness of twin relationships.Nancy L. Segal, Ph.D. is professor of psychology at California State University, Fullerton and director of the Twin Studies Center. She has authored over 250 scientific articles and six books on twins and twin development. She lives in Southern California. She can be followed on Twitter at @nlsegal.Eugenio Duarte, Ph.D. is a psychoanalyst and clinical psychologist practicing in Miami. He treats individuals and couples, with specialties in gender and sexuality, eating and body image problems, and relationship issues. He is a graduate and faculty of William Alanson White Institute in Psychiatry, Psychoanalysis, and Psychology in New York City and former chair of their LGBTQ Study Group; and faculty at Florida Psychoanalytic Institute in Miami. He is also a contributing author to the book Introduction to Contemporary Psychoanalysis: Defining Terms and Building Bridges (2018, Routledge) and has published on issues of gender, sexuality, and sexual abuse. Learn more about your ad choices. Visit megaphone.fm/adchoices