[1] Segal is the professor of developmental psychology and director of the Twin Studies Center, at California State University, Fullerton.

Segal's main research focuses on human behavior and includes cooperation and competition, altruism, personal bonds, and bereavement.

She studies twins to understand social relationships in the general population, hoping to derive implications for what makes people get along.

Her studies in progress show a modest degree of similarity in virtual twins for general intelligence and special mental abilities.

Segal sees great promise in a related new area of research, epigenomics, which refers to natural chemical modifications that take place in individual genomes, marking them for increased or decreased activity.

Over the years, Segal has served as an expert witness on legal cases involving twins, in particular, wrongful death, injury, medical negligence, and custody.

[3] Segal's book, Born Together-Reared Apart: The Landmark Minnesota Twin Study, was published by Harvard University Press in June 2012.

It tells the story of identical twin girls born in Spain's Canary Islands, one of whom was accidentally exchanged for a singleton infant.

This book, which resulted from a festschrift in honor of her mentor Professor Daniel G. Freedman at the University of Chicago, brings together a series of current papers on behavioral-genetic, ethological, cultural and evolutionary approaches to human behavior.