Researcher's New Book Delves Into Twin Psychology

"Indivisible By Two" is the title of Nancy Segal's new book, a collection of essays about the twins, triplets and quadruplets she has studied at Cal State Fullerton's Twin Studies Center and elsewhere over the past decade. To be published by Harvard University Press this fall, it combines human interest stories with scientific observation in a way that promises to inform and entertain at many different levels.

"There is a lot of richness going on in twins' lives," says Segal, a professor of psychology. "This kind of book provides an in-depth look at twins' lives; in the past, people have studied twins either from a purely scientific or human interest perspective, but they haven't studied them from both sides."

The book, however, is merely the latest in a long list of ongoing efforts generated by both Segal and the Twin Studies Center, which has been operated at Cal State Fullerton since 1991. Most recently, Segal was named Cal State Fullerton's Outstanding Professor for 2005 - the highest honor the university awards to a faculty member - in recognition of her research, teaching and scholarly work. She has appeared lately on television in such programs as "Good Morning America" and "Oprah" to discuss the remarkable similarities of and differences between identical twins. She will be included in a "Discovery" documentary on twins that will air next year.

A fraternal twin herself, Segal has been interested in the study of twins since she was a child. Segal's last book, "Entwined Lives: Twins and What They Tell Us About Human Behavior," (Plume, $16) is often cited in the popular press. And she is quoted on such wide-ranging, twin-related topics as the issues facing the Olsen twins, Mary Kate and Ashley, the case of Juan Barbachano - who began life as Juanita, part of a set of identical female twins - and the tragedy of the Baltimore Ravens' rookie Devard Darling, who lost his twin brother, Devaughn, in an off-season workout at Florida State University in 2001.

The Barbachano case, in particular, is fascinating to scientists because by studying Juan and his twin Segal says. "Here are two identical twins - one is perfectly happy with her gender, but for the other, being female has always created conflict. If their DNA is the same, why is there this difference?

"We're looking at the influences of genes and environments, and trying to determine the influence each has," she says. "This benefits everyone."

Regarding the Olsens, Segal was quoted in a story by the Knight Ridder/Tribune News Service in the context of how people view identical twins as a collective entity rather than as individuals. Because they show an early tendency to act alike and engage in all the same activities, being a twin can mean having a figurative clone in the eyes of strangers, friends and even family.

Following Devard Darling's tragedy, newspapers quoted Segal about the devastation twins feel when they lose their sibling. "Twin loss is such a profound, enduring loss," Segal said. "Many identical twins try to keep their twin alive by pursuing the things they did together. Playing football is his way of keeping his brother alive."

In addition to her books and her ongoing discussions with the media, Segal has received a $115,000 grant from the National Institute of Mental Health for the TAPS program, a collaborative effort with the University of San Francisco, to study Twins, Adoptees, Peers and Siblings. A group of graduate students assists on the study under Segal's supervision and that of other faculty members. The study covers new ground, because it includes "virtual twins," as well as the more common biological siblings. Virtual twins are children who were adopted at the same time and who are the same age. The study also includes their siblings and friends.

"I've studied many aspects of twins, and worked with students for years in helping them study twins," Segal says. "I like getting my information out to the public."

In addition, she adds, her subjects are excited about her work and are more than willing to be studied. "Twins love being twins. It's as if they have something special that most people don't."