Twin studies have been highly valuable for estimating the inheritability of certain traits, including academic ability, personality, and interests; family and social relationships; mental and physical health; and physiological measurements. Researchers have been particularly interested in the prevalence of psychopathology, substance abuse, divorce, leadership, and other traits and behaviors related to mental and physical health, relationships, and spirituality. Research suggests that genetics play a strong role in the development of personal characteristics by serving as a blueprint for physical, social, and emotional development. Twins separated at birth and reared in different families have 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. Researchers have produced surprising results showing that social attitudes, behavior, and dental health all have a genetic influence.
Consensus amongst the scientific world is that behavior can be explained by a combination of both nature (genetics) and nurture (environment). This leads to the conclusion that similarities between twins are due to genetics and the differences between twins reared apart are due to the environment. Heredity is an important determining factor in shaping physical appearance, mental acuteness, preferences, personal characteristics, and personality. Researchers have uncovered remarkable similarities between twins raised in separate homes with different parents to be remarkably strong. Examination and scrutiny 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. The inheritability of academic ability, personality and interests, family and social relationships, mental and physical health, and other physiological measurements has inferred correlations for children raised outside their genealogical, biological, and ancestral groupings, but psychologists are not satisfied to rest on that conclusion alone.
Questions still remain regarding to what degree certain behavioral traits can be explained by genetics and the environment. Many studies have been conducted to understand how siblings interact and influence one another, how family environment has an impact on the mental health of adolescents, and how adoptive families are similar to and different from biological families. Extensive research on environmental and biological influences on adopted children and children biologically related to the parents has allowed sibling and parental influences to also be incorporated into the research. The Minnesota Twin Family Study has provided scientists a clearer understanding of the role of genes and environment on human development. The landmark series of investigations have helped identify genetic and environmental influences on the development of psychological traits; findings that have received both praise and criticism. On multiple measures of personality and temperament, occupational and leisure-time interests, and social attitudes twins raised apart were found to be about as similar as those reared together. This evidence for the strong inheritability of many psychological traits should never detract from the value or importance of parenting, education, and other interventions.