The controversy over the role of nature versus nurture in development continues to this day. More than 100 years ago, Sir Francis Galton initiated the study of twins as a means of elucidating the interaction of heredity and environment. He remarked: "There is no escape from the conclusion that nature prevails enormously over nurture when the differences of nurture do not exceed what is commonly found among persons of the same rank of society and in the same country." This statement has remained a challenge, to be refuted or confirmed by further research.
Identical twins reared apart are very rare. Yet their value for investigations of the origins of both normal and abnormal characteristics is inestimable.
In this book, Dr. Juel-Nielsen reports on a longitudinal study of 12 pairs of monozygotic twins, aged 12 to 77 years, who grew up in different environments in Denmark. After describing the collection and selection of material for investigation, Dr. Juel-Nielsen explains the methods of research, which included extensive interviews, medical examinations, and psychometric assessments. He then presents the results in terms of similarities and differences in general health, intelligence, personality traits, and physical and mental disorders. These results are considered in the light of the differing environmental influences.
Dr. Juel-Nielsen's original study was carried out over the period 1954-1959. This new volume includes for the first time the results of a 20-year follow-up study, completed in 1979. Additional information is provided about the subsequent life course of the twins, their mental and physical health, and the causes of death. As Dr. Peter B. Neubauer writes in his Foreword, this "is a book that deserves to be read many times, for it is a vital resource for all those who study the complex interrelationship between environment and development, between norm and pathology during the life cycle."
- Niels Juel Nielsen, M.D., is Professor of Psychiatry at the University of Odense and Superintendent of the Department of Psychiatry at the Odense University Hospital, Denmark. He has represented the field of psychiatry on the Danish Medical Research Council since 1973.
Author(s): Niels Juel-Nielsen, Peter B. Neubauer, Irving I. Gottesman
Publisher: International Universities Press
Year: 1980
Language: English
Commentary: expanded version of original 1965 edition
Pages: 468
Tags: 1965, behavioral genetics, twin studies, adoption studies, monozygotic twin adoption study (MZA), Denmark, nature vs nurture, heritability, intelligence, personality, schizophrenia, Wechsler-Bellevue intelligence test, Raven’s Progressive Matrices intelligence test, Rorschach test, Rapaport word association test, longitudinal study, narcissism, cancer, hypertension, alcoholism, depression, EEG, EKG, test-retest reliability
- "Foreword", Peter B. Neubauer
- "Introduction", Irving I. Gottesman
PART I
- Chapter 1. "Heredity and Environment"
- Chapter 2. "Aims of the Investigation"
- Chapter 3. "Psychiatric-Psychological Twin Research"
-- The twin method
-- Use in psychiatric-psychological research
-- The ''classical'' twin method and the concordance-discordance concept
-- Special twin methods
-- Social and psychological aspects of being a monozygotic twin
- Chapter 4. "Previous Investigations of Monozygotic Twins Reared Apart"
-- _Newman, Freeman & Holzinger_
-- _Shields_
MATERIAL
- Chapter 5. "Collection and Selection of Material"
-- Brief account of the history of the investigation
-- Criteria Of selection
-- Material from the twin register
-- Material from other sources
-- Discussion of the collection and the selection of material
- Chapter 6. "The Investigation Material"
-- Sex
-- Age distribution
-- The separation
--- Time of separation
--- Reasons for separation
--- Age, marital status and occupation of the biological parents
--- Direct or subsidiary causes of separation
METHODS
- Chapter 7. "Investigation Methods"
-- Medical-psychiatric interviews
--- Collection of supplementary information
-- Medical-psychiatric examinations
-- Psychometric methods
--- General methods of testing
--- The Wechsler-Bellevue Test
--- Raven's Progressive Matrices
--- Rorschach's Test
--- Rapaport's Word Association Test
-- Discussion of the psychiatric-psychological methods
- Chapter 8. "Determination of Zygosity"
-- Results of the zygosity determination
-- Discussion of zygosity determination
RESULTS
- Chapter 9. "Intra-pair Differences and Similarities"
-- General Health
--- Height and weight
--- Cardiological examination
--- Neurological examination
--- Electroencephalographic examination
--- Ophthalmological examination
--- Other examinations and conditions
-- Somatic diseases
-- Intelligence and personality
--- Intelligence
--- Personality
-- Psychiatric Disorders
- Chapter 10. "Environmental Differences and Similarities"
- Circumstances before separation
-- The birth
-- Breast feeding
-- Early psychological circumstances
- Social, psychological and inter-personal conditions during upbringing
- Chapter 11. "Psychometric Investigations"
-- Intelligence testing
--- Wechsler-Bellevue Intelligence Scale, Form 1
--- Inter-individual differences
--- Intra-individual differences (Test-retest)
--- Intra-class differences
--- Raven's Progressive Matrices
--- Inter-individual differences
--- Intra-pair differences
--- Comparison of W-B and Raven-test results
-- Personality testing
--- Rorschach's Test
--- Word Association Test (a.m. Rapaport)
--- Summary of the results and conclusions of the psychometric investigations
GENERAL DISCUSSION AND CONCLUSIONS
- Chapter 12. "Influence of Material and Methods on the Results"
-- Results and general conclusions
-- Some general and final comments
-- _Summary_
-- Elementary tables A, B and C
-- Twin Pair Index
-- References
PART II
- "Case Material"
PART III
- Chapter 13. "Follow-up: Twenty-five Years Later"
