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Born Together Reared Apart: The Landmark Minnesota Twin Study

by Nancy L Segal Harvard University Press
Pub Date:
Hbk 416 pages
AU$123.00 NZ$126.96
Product Status: Available in Approx 14 days
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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 as 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.


1. The Jim Twins (February–March 1979)

2. 15,000 Questions × 137 Pairs

3. Early Findings (1979–1983)

4. Sexual Orientation, Cognition, and Medical Traits (1984–1987)

5. Pivotal Papers: Personality and IQ (1988 and 1990)

6. Job Satisfaction, Cardiac Characteristics, and More (1989–1990)

7. Psychopathology and Religiosity (1990)

8. Dental Traits, Allergies, and Vocational Interests (1991–1992)

9. Creativity, Work Values, and Evolution (1992–1993)

10. Family Environments, Happiness, Sensation Seeking, and the MMPI (1994–1997)

11. "Larks" and "Owls," Ego Development, and Authoritarianism (1998–2002)

12. Twin Relationships, Social Attitudes, and Mental Abilities (2003–2005)

13. Sexual Development, Fluctuating Asymmetry, Body Size, and the Structure of Intelligence (2006 and Beyond)

14. Questions, Answers, and Twin Studies of the Future

Appendix A: Funding Sources

Appendix B: Glossary




Twins separated at birth are endlessly fascinating and give us some of the best scientific insights into nature and nurture. No one can tell this story better than Nancy Segal, gifted scientist, raconteur, and wise observer of human nature.
- Steven Pinker, author of The Better Angels of Our Nature

This is a vivid and intimate account of one of the classic episodes in the history of the nature-nurture debate by somebody who was part of the team. The Minnesota Study of Twins Reared Apart made a vital difference, against often entrenched conventional wisdom, to the understanding of human development. Nancy Segal tells the story of the project superbly.
- Matt Ridley, author of Nature via Nurture

Born Together-Reared Apart is a tour-de-force in the history of psychology and twin research. Describing the twins' life stories as well as the scientific data, Segal gives us a compelling account of the findings, implications, and controversies from the world famous Minnesota Study of Twins Reared Apart. The book will be essential for anyone seriously interested in the genetic and environmental influences affecting human health and behavior.
- Robert Plomin, Professor of Behavioral Genetics, King's College London

If you harbor any curiosity about why people turn out the way they do, Segal's topic will fascinate. How big are the effects of nature, nurture and everything else? ...A joy to read when she describes the awe of reuniting twins--and the joy of seeing many become soul mates before her eyes.
- Bryan Caplan, Wall Street Journal

In this inclusive overview, Nancy Segal...examines the study that turned ideas on parenting, teaching, health and sexual orientation upside down.

No study of twins has generated as much publicity, media attention, and discussion in the field of behavior genetics as the Minnesota Study of Twins Reared Apart (MISTRA)… All readers will find Born Together - Reared Apart a highly valuable account of the entire project.
- Dorret I. Boomsma, Science

Segal has provided a thorough history and detailed analysis of the Minnesota Study of Twins Reared Apart (MISTRA), a multi-decade investigation that, she convincingly argues, influenced a paradigm shift in U.S. psychology.
- J. Mercer, Choice

In Born Together--Reared Apart, [Segal] has written a meticulous and fascinating account of the study that involved a total of 137 pairs of twins, including 81 identicals raised apart, mainly from the USA and the UK. It wasn't the first study of its kind, but it was the largest and certainly the most influential.
- Tim Spector, Lancet

It is an important book because many of the study's findings were serious contributions to our bed of knowledge and the book explains why...An important read for any one seriously interested in genetics or the [Nature-Nurture] debate...If you are a professional associated with genetics you will find this book of interest and of value. For those engaged in the Nature-Nurture debate it may be crucial in understanding what traits may be more influenced by nature and which by nurture, and for the layperson it will be of interest for the anecdotes about the twins themselves and how a major study evolved and fared.
- Milton Diamond, Twin Research and Human Genetics
Nancy L. Segal is Distinguished Professor in Humanities and Social Sciences and Director of the Twin Studies Center at California State University, Fullerton.