Twin Research: Biology, Health, Epigenetics, and Psychology is a comprehensive, applied resource in twinning and twin studies that is grounded in the most impactful findings from twin research in recent years. While targeted to undergraduate and graduate students, this compendium will prove a valuable resource for scholars already familiar with twin studies, as well as those coming to the field for the first time. Here, more than forty experts across an array of disciplines examine twinning and twin research methodologies from the perspectives of biology, medicine, genetic and epigenetic influences, and neuroscience. Chapters provide clear instruction in both basic and advanced research methods, family and parenting aspects of twinning, twin studies as applied across various disease areas and medical specialties, genetic and epigenetic determinants of differentiation, and academic, neurological and cognitive development. The presentation of existing studies and methods instruction empowers students and researchers to apply twin-based research and advance new studies across a range of biomedical and behavioral fields, highlighting current research trends and future directions.

The identical "Jim twins" were raised in separate families and met for the first time at age thirty-nine, only to discover that they both suffered tension headaches, bit their fingernails, smoked Salems, enjoyed woodworking, and vacationed on the same Florida beach. This example of the potential power of genetics captured widespread media attention in 1979 and inspired the Minnesota Study of Twins Reared Apart. This landmark investigation into the nature-nurture debate shook the scientific community by demonstrating, across a number of traits, that twins reared separately are as alike as those raised together. As a postdoctoral fellow and then as assistant director of the Minnesota Study, Nancy L. Segal provides an eagerly anticipated overview of its scientific contributions and their effect on public consciousness. The study's evidence of genetic influence on individual differences in traits such as personality (50%) and intelligence (70%) overturned conventional ideas about parenting and teaching. Treating children differently and nurturing their inherent talents suddenly seemed to be a fairer approach than treating them all the same. Findings of genetic influence on physiological characteristics such as cardiac and immunologic function have led to more targeted approaches to disease prevention and treatment. And indications of a stronger genetic influence on male than female homosexuality have furthered debate regarding sexual orientation.

Twin Mythconceptions: False Beliefs, Fables, and Facts about Twins sheds new 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, the book 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, and more. Five appendices cover selected topics in greater depth, such as the frequency of different twin types and the varieties of polar body twin pairs. This book will inform and entertain behavioral and life science researchers, health professionals, twins, parents of twins, and anyone interested in the fascinating topic of twins.

The January 2018 headline story in the Los Angeles Times was riveting. Andrew from the United States and Elad Dvash-Banks from Israel married in Canada in 2010 when gay couples could not marry in these countries. The couple conceived fraternal twins, Aiden and Ethan, with a Canadian surrogate by means of egg and sperm donation. The two boys were born just four minutes apart. While unplanned given the uncertainties of in vitro fertilization, Aiden was fathered by Andrew and Ethan was fathered by Elad, Andrew and Elad wished to raise their children in the United States, but when they arrived at the American Consulate in Toronto to apply for citizenship, a staff member fired off a series of "shocking" and humiliating questions, and informed the couple of her authority to require a DNA test to determine each parents' relatedness to each twin--she warned that without these tests neither twin would be granted US citizenship. Andrew and Elad knew which twin each had fathered and had planned on keeping this information confidential. They knew this because DNA analyses had already been performed, but the consulate insisted that these costly tests be repeated using their designated laboratory. Having no alternative, DNA testing was arranged, and results submitted to the consulate. Soon, two envelopes arrived at their home, bearing both welcome and dreaded news: United States citizenship was offered to Aiden, whose father was a US citizen, but not to Ethan, whose father was Israeli. And, thus, their ground-breaking legal journey began. The couple's high-profile lawsuit nearly reached the US Supreme Court, capturing worldwide attention along the way. Nancy Segal brings the story to life through firsthand accounts of each man's life history and analysis of the legal intricacies that threatened to keep this loving family out of the US.

A leading expert on twins delves into the stories behind her research to reveal the profound joys and real-life traumas of twelve remarkable sets of twins, triplets, and quadruplets.

"Indivisible by Two" introduces us to an assortment of memorable characters, from the "Fireman Twins"--brothers who, though reared separately, are astonishingly similar in personality and behavioral traits--to the twin sisters who overcame one twin's infertility by having the other serve as her surrogate mother. We meet one of the few identical brother-sister pairs in the world after one of two sisters was surgically transformed into a man, and identical triplet brothers, only one of whom is gay while the others are straight. We see uniquely blended families--identical twin brothers marrying identical twin sisters, and Chinese twins adopted by different Canadian families yet raised as sisters.

Being a twin can also render the experience of historical tragedy uniquely painful. We meet Stepha and Annetta, survivors of Josef Mengele's heinous experiments in Auschwitz, and untangle the troubled lifelong tie between Jack and Oskar, born in the 1930s to a Jewish father and a German Gentile mother, one raised as a Jew in Trinidad and the other as a Catholic and a member of the Hitler Youth in Nazi Germany.

Segal unravels these stories and others with an eye for the challenges that life as a twin (or triplet or quadruplet) can pose to parents, friends, and spouses, as well as the twins themselves. These moving stories remind us how incompletely any theory explains real life--twin or not.

Takes the first in-depth look at the New York City adoption agency that separated twins and triplets in the 1960s, and the controversial and disturbing study that tracked the children's development while never telling their adoptive parents that they were raising a "singleton twin." In the 1960s, New York City's Child Development Center launched a study designed to track the development of twins and triplets given up for adoption and raised by different families. The controversial and disturbing catch? None of the adoptive parents had been told that they were raising a twin-the study's investigators insisted that the separation be kept secret. Here, Nancy Segal reveals the inside stories of the agency that separated the twins, and the collaborating psychiatrists who, along with their cadre of colleagues, observed the twins until they turned twelve. This study, far outside the mainstream of scientific twin research, was not well-known to scholars or the general public until it caught the attention of documentary filmmakers whose recent films, Three Identical Strangers and The Twinning Reaction, left viewers shocked, angered, saddened and wanting to know more. Interviews with colleagues, friends and family members of the agency's psychiatric consultant and the study's principal investigator, as well as a former agency administrator, research assistants, journalists, ethicists, attorneys, and-most importantly--the twins and families who were unwitting participants in this controversial study, are riveting. Through records, letters and other documents, Segal further discloses the investigators' attempts to enagge other agencies in separating twins, their efforts to avoid media exposure, their worries over informed consent issues in the 1970s and the steps taken toward avoiding lawsuits while hoping to enjoy the fruits of publication. Segals' spellbinding stories of the twins' separation, loss and reunification told in Deliberately Divided offer readers the behind-the-scenes details that, until now, were lost to the archives of history.