Cal State Fullerton psychology professor and twin studies scholar Nancy L. Segal is fascinated by how twins are alike and different.
Segal, a fraternal twin, has dedicated her scholarly work over the past three decades to advancing knowledge on the importance of genetics in shaping human behavior.
Her research interests lie at the juncture of developmental psychology, genetics, evolutionary psychology and twin studies. Segal is the founder and director of the Twin Studies Center, a treasure trove of twin-related materials, located in the Humanities-Social Sciences Building.
For her outstanding scholarly work and breadth of scientific research, Segal is the recipient of the university’s 2026 L. Donald Shields Excellence in Scholarship and Creativity Award.
“With her expertise, Dr. Segal continues to inspire and educate scholars, health care professionals, and the public on the fascinating discoveries within twin research and the broader implications for human development,” said Jessica Yirush Stern, dean of the College of Humanities and Social Sciences.
Segal, who holds a doctorate from the University of Chicago, is regarded as a leading international expert in twin research and has conducted numerous groundbreaking studies. She is the only researcher in the world to study “virtual twins,” same-age, unrelated siblings raised together since infancy.
Her body of academic work includes helping British-born twins reunite on the CSUF campus after 78 years apart — the longest such gap ever recorded. Segal’s 2014 study earned these twins a Guinness World Records title and made her the publication’s go-to expert on twins.
One of her recent books — she’s authored 10 and is working on an 11th — tells the story of identical male twins from Colombia, South America, who were switched at birth. She was featured in a Netflix documentary about the separated brothers, “The Accidental Twins,” released in 2024.
Segal also published an annotated book collection of photographs of twin children who survived the Auschwitz-Birkenau death camp during the Holocaust. Some of her latest work focuses on gay fathers, one a U.S. citizen and the other an Israeli, with twin sons. Her study highlights the couple’s high-profile lawsuit to secure U.S. citizenship that was denied to one of their twins.
Eriko Self, professor of psychology, called her colleague “a star on our campus, as well as at national and international levels.”
“Her reputation as a productive and creative scholar who has substantially advanced the field’s basic scientific understanding of psychology in scholarly and creative ways is without equal,” said Self, who nominated Segal for the award.
In 1991, when Segal joined the university, she founded the Twin Studies Center to foster twin research by students and faculty. The center also provides information and support to professionals and the public.
Over the decades, Segal has authored more than 400 academic articles, including many with her students, published in leading psychology publications. She has mentored scores of undergraduate and graduate students, many of whom went on to earn master’s degrees and doctorates.
Segal, who has received numerous accolades and has made hundreds of media appearances, is also the recipient of CSUF’s 2005 Outstanding Professor Award and the California State University’s 2016 Wang Family Excellence Award.
She has also been invited to make scholarly presentations, lectures, podcasts and three TEDx Talks about her twin research to faculty, students and professionals around the world. “Teaching and research are closely intertwined,” she said. “My diverse research experiences have kept my teaching, mentoring and presentations current and lively.”