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Born Together—Reared Apart

Born Together—Reared Apart: The Landmark Minnesota Twin Study

Copyright Date: 2012
Published by: Harvard University Press
Pages: 416
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  • Book Info
    Born Together—Reared Apart
    Book Description:

    The Minnesota Study of Twins Reared Apart startled scientists by demonstrating that twins reared apart are as alike, across a number of personality traits and other measures, as those raised together, suggesting that genetic influence is pervasive. Segal offers an overview of the study’s scientific contributions and effect on public consciousness.

    eISBN: 978-0-674-06515-4
    Subjects: Psychology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. Introduction
    (pp. 1-16)

    Columbia University professor Walter Mischel has been a prominent figure in personality assessment and the study of emotional control. He is also the 2011 recipient of the prestigious Grawemeyer Award for contributions to psychology. The passage quoted above, from his well-known undergraduate textbook, largely reflected 1970s’ and early 1980s’ views on factors affecting behavioral development, but it would not appear in textbooks today.¹ It has been replaced by statements such as, “Currently, most kinship findings support a moderate role for heredity. . . . Heritability research also reveals that genetic factors are important in personality.”² This shift in perspective, from...

  4. CHAPTER ONE The Jim Twins (February–March 1979)
    (pp. 17-31)

    On February 19, 1979, the Lima News in Ohio reported the reunion of thirty-nine-year-old identical twins Jim Lewis and Jim Springer, separated at four weeks of age (Figure 1-1). The twins, born to an unwed mother, had been placed in the Knoop Children’s Home in Troy, Ohio, and had been adopted separately by two local families. They grew up forty miles apart, Lewis in Lima and Springer in Piqua.¹

    The couples who adopted the twins were Jess and Sarah Springer, and Ernest and Lucille Lewis. Both families had been told that their child was a twin whose brother had died....

  5. CHAPTER TWO 15,000 Questions × 137 Pairs
    (pp. 32-64)

    The MISTRA evolved rapidly following the Jim twins’ 1979 assessment, especially with respect to methodology—how we found the twins, what we asked them to do, and where we had them do it. This chapter provides detailed descriptions of the participants, test schedule, genetic terms, and statistical concepts needed to understand the inner workings and quantitative findings of the project.

    From the start, each twin completed protocols such as a life history interview (covering their separation, reunion, contact, residential history, and rearing family composition), personality and interest questionnaires, and the Wechsler IQ test. We added tests and questionnaires (such as...

  6. CHAPTER THREE Early Findings (1979–1983)
    (pp. 65-81)

    The third International Congress on Twin Studies, held in Jerusalem, Israel, in 1980, was an opportunity to present preliminary findings from the MISTRA and to introduce the study to twin research colleagues from around the world. The first two presentations in Jerusalem were largely qualitative in nature, quite different from the quantitative treatment of the data as the sample grew. These early cases suggested that possible life-history factors were associated with the co-twins’ differences in selected behaviors. For example, twins in one MZA pair did not share their fear of snakes, a difference traceable to one twin having been bitten...

  7. CHAPTER FOUR Sexual Orientation, Cognition, and Medical Traits (1984–1987)
    (pp. 82-96)

    In 1984, I had been working on the MISTRA for two years. Every pair I studied provided a unique take on nature-nurture questions. MZA twins Bill and Tim showed the same side-to-side sway as they walked. MZA twins Stan and Mitch were both homosexual despite being reared apart their entire lives. Greater insight into the twins’ behavioral and physical similarities and differences began to emerge from the analyses we conducted between 1984 and 1987. Many of our findings continued to be reported in the press.

    The MISTRA had matured greatly since my arrival in 1982. The number of empirical papers...

  8. CHAPTER FIVE Pivotal Papers: Personality and IQ (1988 and 1990)
    (pp. 97-115)

    Daniel Goleman of the New York Times published the conclusion to our first major analysis of the personality data before it appeared in a scientific journal. In fact, he used our conclusion as his opening lines. The University of Minnesota’s public affairs office provided Goleman with a draft of the study approximately eighteen months before its 1988 publication in the Journal of Personality and Social Psychology.² Bouchard had told the university’s public relations representative that the paper would be published, but he did not give it to her. He explained to her that rules prohibited the release of scientific findings...

  9. CHAPTER SIX Job Satisfaction, Cardiac Characteristics, and More (1989–1990)
    (pp. 116-135)

    The Science IQ paper was a key accomplishment during the years 1988–1990, but not the only one. Our study of job satisfaction was the first attempt by anyone to examine genetic influence on the workplace experience. During these years, we also reported analyses of the electrical conductance of the skin, heart rate, special mental abilities, information processing, psychopathology, religiosity, intelligence, and personality. The choice of behaviors to be analyzed, and when, were affected by the amount of accumulated data, significant twin findings reported by other laboratories, and personal time available to the investigators. Most of our analyses concerned intelligence and...

  10. CHAPTER SEVEN Psychopathology and Religiosity (1990)
    (pp. 136-152)

    I learned about Tourette syndrome when I was a graduate student assistant at the Illinois State Psychiatric Institute in Chicago between 1974 and 1982. I noticed someone there who showed continual grunting and clearing of the throat, and periodic twirling of a lock of hair with the forefinger of one hand. I asked one of my supervisors about these behaviors, and he said, “Tourette.”

    Tourette syndrome was first described in 1885 by the French neurologist Georges Gilles de la Tourette.¹ The symptoms are distinctive—they include involuntary motor and phonic tics that appear by age seven, but they can appear...

  11. CHAPTER EIGHT Dental Traits, Allergies, and Vocational Interests (1991–1992)
    (pp. 153-170)

    Pediatric dentist Michael J. Till’s career began at the Naval Air Academy station in southwest Texas where he transported patients’ files to the dental office. Till, retired from the University of Minnesota at the time of this writing, deserves full credit for the dental component added to the MISTRA in 1980. Till had read about the MISTRA in the campus newspaper and saw the potential for dental research. When I met him in 2009 at the University Marriott Hotel, he recalled the “fun days” when twins came to his clinic.

    When the MISTRA dental study began, several reared-together twin studies...

  12. CHAPTER NINE Creativity, Work Values, and Evolution (1992–1993)
    (pp. 171-194)

    David T. Lykken was brilliant and funny, frank and controversial. He enjoyed hearing other people’s ideas and had many of his own, some hotly contested. He deprecated lie detection¹ and advocated parental licensure, the issuing of permits to couples who met government standards for reproducing.² Lykken was also a skilled writer and storyteller. He supplemented his scientific concepts and conclusions with real-life examples, many drawn from his experiences with the reared-apart twins.³

    Lykken was also a clever methodologist. He showed how statistical power increased by 20 percent by studying twins reared apart versus twins reared together.⁴ In twin research, he...

  13. CHAPTER TEN Family Environments, Happiness, Sensation Seeking, and the MMPI (1994–1997)
    (pp. 195-220)

    Between the years 1994 and 1997, the MISTRA published papers on a number of new research topics. The twins showed that current perceptions of the past are genetically influenced, people have happiness set-points, and practice does not always lead to perfect performance. They also showed that there was genetic influence on the personality correlates of psychopathology on the Minnesota Multiphasic Personality Inventory (MMPI), and that the same genes affected impulsivity and sensation seeking. By the start of 1994, nearly 130 pairs had been studied.

    Graduate student Yoon-Mi Hur (now a faculty member at Mokpo National University in South Korea) joined...

  14. CHAPTER ELEVEN “Larks” and “Owls,” Ego Development, and Authoritarianism (1998–2002)
    (pp. 221-245)

    Some people get up early and work best at six in the morning (“larks”), while others like to sleep late and work into the night (“owls”). Most people know which type they are, but don’t know how they got that way. In 1998, Yoon-Mi Hur and Bouchard examined “morningness” and “eveningness”—and these tendencies, like most measured traits, showed genetic effects. This finding, which occurred relatively late into the study, was understandably less surprising than the detection of a genetic influence on habits, fears, and medical traits that were suggested with our earliest pairs. This shift in thinking began with...

  15. CHAPTER TWELVE Twin Relationships, Social Attitudes, and Mental Abilities (2003–2005)
    (pp. 246-265)

    Outside a shopping mall, thirty-eight-year-old Marty and Stephanie stared at each other in a bewildered daze, touching each other’s faces and hair as if they were their own. After several minutes they joined hands, jumping up and down with glee. Thirty-four-year-old Jim and Trent exited their cars on a stretch of Texas highway. They approached one another slowly, shook hands, asked the other simultaneously how they were “after all these years,” then started laughing. Reunited identical triplets Bob, Dave, and Eddy met one another on two occasions when they were just nineteen—first Bob and Eddy, then Dave and Bob...

  16. CHAPTER THIRTEEN Sexual Development, Fluctuating Asymmetry, Body Size, and the Structure of Intelligence (2006 and Beyond)
    (pp. 266-297)

    I am looking at the calendar as I write this last chapter on the MISTRA’s findings. It is July 1, 2010, and I know that later today thirty-five-year-old Hanan Hardy will travel to Morocco to meet her twin sister Hassania for the first time. The twins, who appear to be MZ, were separated at birth because their biological mother could not care for them. Hanan was reared in the United States by their mother’s close friend and enjoyed middle-class privileges; Hassania remained in Morocco and was sold to another family when she was just one week old, living in poverty...

  17. CHAPTER FOURTEEN Questions, Answers, and Twin Studies of the Future
    (pp. 298-328)

    No one could satisfy the MISTRA’s critics while the study was in progress, but I have the benefit of time. Over thirty years have passed since the project began, and over ten years have passed since it ended. The bitter 1970s nature-nurture debates have largely (but not completely) subsided as evidence of genetic influence on behavior has accumulated. Most serious scholars have accepted the body of work produced by the MISTRA and related studies, and many individuals have rethought the significance of their own findings in light of this work. Researchers have moved on to explore new and interesting questions...

  18. APPENDIX A: Funding Sources
    (pp. 329-332)
  19. APPENDIX B: Glossary
    (pp. 333-338)
  20. Notes
    (pp. 339-396)
  21. Acknowledgments
    (pp. 397-400)
  22. Index
    (pp. 401-410)