Encyclopedia of Personality and Individual Differences

Living Edition
| Editors: Virgil Zeigler-Hill, Todd K. Shackelford

Segal, Nancy L.

  • Nancy L. SegalEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-28099-8_1810-1



Twin research offers powerful tools for investigating the factors affecting individual differences in personality development.


Dr. Nancy L. Segal is a professor of developmental psychology at California State University, Fullerton (CSUF). She is also the founder and director of the Twin Studies Center, a unit in the Department of Psychology dedicated to promoting psychological twin research and disseminating information to interested colleagues and the public. Prior to her appointment at CSUF, Dr. Segal was associated with the famous Minnesota Study of Twins Reared Apart (MISTRA), at the University of Minnesota. Her twin research on personality and individual differences, conducted with MISTRA colleagues and others, has found genetic influences on the majority of measured personality traits. She has also studied personality similarity in a unique group, namely,...


Personality Trait Twin Study Identical Twin Behavioral Genetic Twin Sister 
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  1. Emma Otta, Eloisa de S. Fernandes, Tiziana G. Acquaviva, Tania K. Lucci, Leda C. Kiehl, Marco A. C. Varella, Nancy L. Segal, Jaroslava V. Valentova. (2016). Twinning and multiple birth rates according to maternal age in the city of São Paulo Brazil: 2003–2014. Twin Research and Human Genetics, 19(6), 679–686.Google Scholar
  2. Kanazawa, S., & Segal, N.L. (2017). Same-sex twins are taller and heavier than opposite-sex twins (but only if breastfed): Possible evidence for sex bias in human breast milk. Journal of Experimental Child Psychology, 156(4), 186–191.CrossRefPubMedGoogle Scholar
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  7. Segal, N. L. (1984a). Cooperation, competition and altruism within twin sets: A reappraisal. Ethology and Sociobiology, 5(3), 163–177.CrossRefGoogle Scholar
  8. Segal, N. L. (1984b). Zygosity diagnosis: Laboratory and investigator’s judgment. Acta Geneticae Medicae et Gemellologiae Twin Research, 33(3), 515–520.CrossRefPubMedGoogle Scholar
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  11. Segal, N. L. (1999/2000). Entwined lives: Twins and what they tell us about human behavior. New York: Dutton Press/Plume.Google Scholar
  12. Segal, N. L. (2002). Co-conspirators and double-dealers: A twin film analysis. Personality and Individual Differences, 33(4), 621–631.CrossRefGoogle Scholar
  13. Segal, N. L. (2005/2007). Indivisible by two: Lives of extraordinary twins. Cambridge, MA: Harvard University Press.Google Scholar
  14. Segal, N. L. (2011). Someone else’s twin: The true story of babies switched at birth. Amherst: Prometheus Books.Google Scholar
  15. Segal, N. L. (2012). Born together – Reared apart: The landmark Minnesota twin study. Cambridge, MA: Harvard University Press.CrossRefGoogle Scholar
  16. Segal, N. L. (2013). Personality similarity in unrelated look-alike pairs: Addressing a twin study challenge. Personality and Individual Differences, 54(1), 23–28.CrossRefGoogle Scholar
  17. Segal, N. L. (25, May 2014). The closest of strangers. New York Times, Sunday Review (Gray Matter), SR12. http://www.nytimes.com/2014/05/25/opinion/sunday/the-closest-of-strangers.html?_r=0.
  18. Segal, N. L., & Cortez, F. A. (2014). Born in Korea – Adopted apart: Behavioral development of monozygotic twins raised in the United States and France. Personality and Individual Differences, 70(2), 97–104.CrossRefGoogle Scholar
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  20. Segal, N. L., & Kanazawa, S. (22, January 2017). “Does Breast Milk Have a Sex Bias?” New York Times, Sunday Review (Gray Matter), SR 8.Google Scholar
  21. Segal, N. L., & Russell, J. (1991). IQ similarity in monozygotic and dizygotic twin children: Effects of the same versus separate examiners: A research note. Journal of Child Psychology and Psychiatry, 32(4), 703–708.CrossRefPubMedGoogle Scholar
  22. Segal, N. L., Weisfeld, G. E., & Weisfeld, C. C. (Eds.). (1997). Uniting psychology and biology: Integrative perspectives on human development. Washington, DC: American Psychological Association Press.Google Scholar
  23. Segal, N. L., Graham, J. L., & Ettinger, U. (2013). Unrelated look-alikes: A replicated study of personality similarity and new qualitative findings on social relatedness. Personality and Individual Differences, 55(2), 169–176.CrossRefGoogle Scholar
  24. Segal, N. L., Goetz, A. T., Maldonado, A. C. (2015a, July 17). The whites of our eyes. New York Times, Sunday Review (Gray Matter), p. SR9.Google Scholar
  25. Segal, N. L., Li, N. P., Graham, J. L., & Miller, S. A. (2015b). Do parents favor their adoptive or biological children? Predictions from kin selection and compensatory models. Evolution and Human Behavior, 36(5), 379–388.CrossRefGoogle Scholar
  26. Segal, N. L., Cortez, F. A., Zettel-Watson, L., Cherry, B. J., Mechanic, M., Munson, J. E., Velázquez, J. M. A., & Reed, B. (2015c). Genetic and experiential influences on behavior: Twins reunited at seventy-eight years. Personality and Individual Differences, 73(2), 110–117.CrossRefPubMedPubMedCentralGoogle Scholar
  27. Segal, N. L., Goetz, A. T., & Maldonado, A. C. (2016). Preferences for visible white sclera in adults, children and autism spectrum disorder children: A test of the cooperative eye hypothesis. Evolution and Human Behavior, 37(1), 35–39.CrossRefGoogle Scholar
  28. Tellegen, A., Lykken, D. T., Bouchard Jr., T. J., Wilcox, K. J., Segal, N. L., & Rich, S. (1988). Personality similarity in twins reared apart and together. Journal of Personality and Social Psychology, 54(6), 1,031–1,039.CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Psychology DepartmentCalifornia State University, FullertonFullertonUSA

Section editors and affiliations

  • Catherine Cottrell
    • 1
  1. 1.Division of Social SciencesNew College of FloridaSarasotaUSA