Dr. Nancy Segal, the world’s leading expert on twins, has a new book that sheds light on over 70 commonly held ideas and beliefs about the origins and development of identical and fraternal twins. Using the latest scientific findings from psychology, psychiatry, biology, and education, Dr. Segal separates fact from fiction. Each idea about twins is described, followed by both a short answer about the truth, and then a longer, more detailed explanation. Coverage includes embryology of twins, twin types, intellectual growth, personality traits, sexual orientation of twins, marital relationships, epigenetic analyses, the frequency of different twin types and the varieties of polar body twin pairs. This book, and Salon with Dr. Segal, will inform and entertain behavioral and life science researchers, health professionals, twins, parents of twins, and anyone interested in the fascinating topic of twins and what they can teach us about human nature. Dr. Segal earned her Ph.D. in the Social Sciences and Behavioral Sciences from the University of Chicago. From 1982-1991 she was a post-doctoral fellow and research associate at the University of Minnesota, affiliated with the well-known Minnesota Study of Twins Reared Apart. She is currently Professor of Psychology at CSU Fullerton and Director of the Twin Studies Center, which she founded in 1991. Dr. Segal has authored over 200 scientific articles and book chapters, as well as several books on twins. Her previous book, Born Together-Reared Apart: The Landmark Minnesota Twin Study (2012, Harvard University Press) won the 2013 William James Book Award from the American Psychological Association. Her other books include Someone Else’s Twin: The True Story of Babies Switched at Birth (2011), Indivisible by Two: Lives of Extraordinary Twins (2007) and Entwined Lives: Twins and What They Tell Us About Human Behavior (2000). She is the 2016 recipient of the Wang Family Excellence Award from the California State University administrators and trustees for “exemplary contributions and achievement.” She was recognized as CSUF’s Outstanding Professor of the Year in 2005 and as the Distinguished Faculty Member in Humanities and Social Sciences in 2007 and 2014. She has been a frequent guest on national and international television and radio programs, including the Martha Stewart Show, Good Morning America, the Oprah Winfrey Show and The Forum (BBC). Dr. Segal has variously served as a consultant and expert witness for the media, the law and the arts.