The Minnesota Twin Family Study (or MTFS) is a longitudinal study

Longitudinal study

A longitudinal study is a correlational research study that involves repeated observations of the same variables over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the...

 of twin

Twin

A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic , meaning that they develop from one zygote that splits and forms two embryos, or dizygotic because they develop from two separate eggs that are fertilized by two separate sperm.In contrast, a fetus...

s conducted by researchers at the University of Minnesota - Twin Cities. It seeks to identify the genetic and environmental influences on the development of psychological

Psychology

Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 traits.

Principal investigators are David T. Lykken

David T. Lykken

David Thoreson Lykken was a behavioral geneticist and Professor Emeritus of Psychology and Psychiatry at the University of Minnesota...

, Ph.D., Matt McGue, Ph.D., William Iacono, Ph.D., and Kevin Haroian, B.A. It involves several independent but related projects:

• Minnesota Twin Registry
• Minnesota Twin Study of Adult Development
• Minnesota Twin Family Study (Male Project)
• Minnesota Twin Family Study (Female Project)
• Sibling Interaction and Behavior Study

Registry

The Minnesota Twin Registry was established in 1983. Its original goal was to establish a registry of all twins born in Minnesota from 1936 to 1955 to be used for psychological research. Recently, it has added twins born between 1961 and 1964. It primarily conducts personality and interests tests with its 8,000+ twin pairs and family members via mail. From this project, it was able to confirm that twins and their families are representative of the population and that a poll of their opinions would be more accurate than polls in the newspaper.

Study

MTFS was established in June 1989 using same-gendered twin pairs age 11 or 17. All twins born in MN at that time were invited to participate using birth registry data. 500 additional 11 year old twin-pairs were added in 2000. Twin studies

Twin study

Twin studies help disentangle the relative importance of environmental and genetic influences on individual traits and behaviors. Twin research is considered a key tool in behavioral genetics and related fields...

 are valuable to researchers because identical twins share 100% of their genes and fraternal twins share, on average, 50% of their genes. Both identical and fraternal twins share certain aspects of their environment (e.g. religious practices in the home). This allows researchers to estimate the heritability of certain traits. Participants are asked about academic ability, personality, and interests; family and social relationships; mental and physical health; physiological measurements. Of interest to researchers are prevalence of psychopathology

Psychopathology

Psychopathology is the study of mental illness, mental distress, and abnormal/maladaptive behavior. The term is most commonly used within psychiatry where pathology refers to disease processes...

, substance abuse

Substance abuse

A substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...

, divorce

Divorce

Divorce is the final termination of a marital union, canceling the legal duties and responsibilities of marriage and dissolving the bonds of matrimony between the parties...

, leadership

Leadership

Leadership has been described as the “process of social influence in which one person can enlist the aid and support of others in the accomplishment of a common task". Other in-depth definitions of leadership have also emerged.-Theories:...

, and other traits and behaviors related to mental and physical health, relationships, and religiosity.

Twins reared apart

In 1979, Thomas Bouchard began to study twins who were separated at birth and reared in different families. He found that an identical twin reared away from his or her co-twin seems to have about an equal chance of being similar to the co-twin in terms of personality, interests, and attitudes as one who has been reared with his or her co-twin. This leads to the conclusion that the similarities between twins are due to genes, not environment, since the differences between twins reared apart must be due totally to the environment.

Sibling interaction and behavior

The Sibling Interaction and Behavior Study (SIBS) is a study of adoptive and biological siblings. Since adopted siblings are not biologically related to each other or their siblings, comparing families in which two siblings are both adopted, families in which one sibling is adopted and one is biologically related to the parents, and families in which both siblings are biologically related to the parents allows environmental and biological influence to be analyzed. It additionally allows sibling influence as well as parental influence to be studied. 617 families participated in the intake phase of this study. All families consisted of two parents and two teenage siblings. The primary purposes of this study are to understand how siblings interact and influence one another, how family environment has an impact on the psychological health of adolescents, and how adoptive families are similar to and different from nonadoptive families.

Adoption

The Twin Study seeks to identify genetic and environmental influences on the development of psychological traits. The value of the research was the ability to estimate the inheritability of certain traits, including academic ability, personality and interests, family and social relationships, mental and physical health, and other physiological measurements. Researchers had also studied the prevalence of psychopathology, substance use, divorce, leadership, and other traits. The relevance of the studies pertained to the importance of heredity as a determining factor in shaping our physical appearance, mental acuteness, preferences, personal characteristics, and personality. Researchers found the similarities between twins raised in separate homes with different parents to be remarkably strong. The research gives significant weight to the importance of genetics as a key factor in determining physical appearance and attributes, as well as personalities and inherent abilities. This research has inferred correlations for all children raised outside their genealogical, biological, and ancestral groupings. Judith and Martin Land, (2011) Adoption Detective: Memoir of an Adopted Child, p. 96-97, 279, acknowledge The Minnesota Twin Family Study as a key reference. Children who are orphaned, fostered, or adopted may have certain behavior or inheritable traits activated by certain environmental factors or adopted parents, but only within the limitations of their genes. American public opinion, with the support of the courts, and national media attention, seek to maintain a benevolent civil approach to the raising of children that discourages profiling and prejudice. For that reason genetic and psychological research of this type is automatically rejected by some groups and individuals.

External links

• Minnesota Center for Twin & Family Research via the University of Minnesota and the Department of Psychology
• Minnesota Twin Family Study website via University of Minnesota
• Minnesota Twin Family Registry: Some initial findings
• "Sources of human psychological differences: the Minnesota study of twins reared apart." Thomas J. Bouchard Jr.; David T. Lykken; Matthew McGue; Nancy L. Segal; Auke Tellegen; Science, Oct 12, 1990 v250 n4978 p223(6)

Further analysis of reared-apart twin research

• Farber, S. L. (1981). Identical twins reared apart: A reanalysis. New York: Basic Books.
• Joseph, J. (2004). The Gene Illusion: Genetic Research in Psychiatry and Psychology Under the Microscope. New York: Algora. (2003 United Kingdom Edition by PCCS Books)
• Joseph, J. (2001). Separated Twins and the Genetics of Personality Differences: A Critique. American Journal of Psychology, 114, 1-30
• Kamin, L. J. (1974). The Science and Politics of I.Q. Potomac, MD: Lawrence Erlbaum Associates.
• Taylor, H. F. (1980). The IQ Game: A Methodological Inquiry into the Heredity-Environment Controversy. New Brunswick, NJ: Rutgers University Press.