Minnesota Twin Registry
Minnesota Twin Study of Adult Development
Minnesota Twin Family Study (Male Project)
Minnesota Twin Family Study (Female Project)

The Minnesota Twin Family Study seeks to identify the genetic and environmental influences on the development of psychological traits. It is the largest research initiative within the Department of Psychology and is composed of several independent projects.

The Minnesota Twin Registry started in 1983 on the premise that all human research is more interesting and informative if twins participate. Its original goal was to establish a registry of all twins born in Minnesota from 1936 to 1955 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 through the mail. From this project, we were 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. Dr. David T. Lykken directs this study. A good description of the study can be found in The Minnesota Twin Registry: Some Initial Findings.

The Minnesota Twin Study of Adult Development began in 1986 to identify what causes individual differences in aging. By studying identical (MZ) and fraternal (DZ) twins, it can estimate how genes and environment affect the aging process. Some of its preliminary findings are the following: (1) Genetic factors appear to influence personality, mental, and activity-level changes as adults become older; (2) Maintaining an active lifestyle will contribute to more successful aging; (3) Continuing to engage in intellectual activities witll help adults retain cognitive functioning as they age; and (4) Keeping an active social life will contribute to stronger feelings of happiness and well being. This study is directed by Dr. Matt McGue.

The Minnesota Twin Family Study started locating male twins born between 1971 and 1982 in 1989. In 1992, it expanded its investigation to female twins born between 1975 and 1986. It is a prospective study of the development of psychological traits like personality and etiology of psychopathology like substance abuse. This project studies the physical, mental, and social changes that occur in twins as they pass from childhood into adolescence and from adolescence into young adulthood. Participants are asked to visit the university for an eight-hour assessment which focuses on four areas: (1)academic ability, personality, and interests, (2) family and social relationships, (3) mental and physical health, and (4) physiological measurements. Participants are contacted annually and revisit the university every three years. Dr. William Iacono directs the male project, and Dr. Matt McGue leads the female project. Questions about this study can be directed to Kevin Haroian, its administrative director. Additional information about twin research findings can be found in the brochure What's Special About Twins to Science? Below is a list of items addressed therein.

How Are Identical (MZ) and Fraternal (DZ) Twins Made?
Can Doctors Tell If Twins Are Identical or Fraternal?
What Accounts for the Similarity Among Twins? Genes or Environment?
What Is This Thing Called Love?
Could Divorce Be Inherited?
Growing Up and Growing Apart?
Resting EEG in Twins
Brain Responses (P300) in Twins

Dr. David T. Lykken
Dr. Lykken, a psychophysiologist and behavior geneticist, has been doing twin research since 1970. He is currently the PI of the Minnesota Twin Registry project (NIMH 37860), and was the PI of the recently completed Twin Study of Alcoholism (supported by NIAAA). Lykken works with the other PIs and graduate students on data analysis. His background and interests relate to many aspects of the study (e.g., analysis of twin data, psychophysiology, personality, psychopathology). With the publication of his new book, "The Antisocial Personalities," he brings special expertise to the study of the link between undersocialized behavior and the development of alcoholism and related disorders.

Dr. Matt McGue
Dr. McGue is a behavioral and quantitative geneticist who is responsible for the development and application of the necessary quantitative methodology for the MTFS. He is also responsible for coordinating data entry and management, and he supervises family recruitment. His major research interests are in the ares of the behavioral genetics of substance abuse and developmental behavior genetics. He is currently the PI of a twin study of normal aging (NIA AG 06886), and like Iacono and Lykken, he has had considerable experience directing large scale studies like the MTFS.List of Dr. McGue's Behavioral Genetics-related publications.

Dr. William Iacono
Dr. Iacono is a clinical psychologist and psychophysiologist who has been concerned with the identification and characterization of psychophysiological measures as prospective markers of psychopathology. In addition to overseeing the MTFS, he is responsible for overseeing the clinical assessment of study participants and the psychophysiological assessment and data analysis. He is also PI on an epidemiological study of first-episode schizophrenia, and he is currently co-investigator with William Grove on a family study of schizophrenia (NIMH 49738) in which psychophysiological measures are being used to characterize familial transmission in schizophrenia. He is also Director of the Neurobehavioral Aspects of Psychopathology and Personality training grant that is part of the clinical psychology doctoral program. List of Dr. Iacono's Twin Study-related publications.

Kevin Haroian
Mr. Haroian, the Study's Administrative Director, has over 15 years of experience working with the PIs and coordinating large research projects. He is also expert in the technical aspects of psychophysiology, laboratory hardward, and real-time computer programming. He provides technical training to the staff, monitors data collection and storage, supervises the day-to-day activities of the project, handles personnel matters and the budget, and maintains project documentation. He is responsible for directing project administration and insuring that the policies and directives of the PIs are implemented.