Societal values, chance and choice affect whether someone chooses to marry, but a new study published in the Journal of Personality and Social Psychology (Vol. 86, No. 2), suggests that genes, too, may play a role, particularly as they influence personality characteristics.
Principal investigator Wendy Johnson, a fourth-year differential psychology graduate student at the University of Minnesota, Twin Cities, and her faculty colleagues there analyzed data from the Minnesota Twin Registry consisting primarily of twin pairs born in Minnesota between 1936 and 1955.
The 7,094 twins had completed the Multidimensional Personality Questionnaire via mailings in the 1980s and reported whether they had ever been married--a category that included common law marriages and long-term cohabitation. Only 10 percent of the participants reported never being married.
The researchers found that identical twins--twins who share 100 percent of their genetic makeup--reported the same marital status more than 88 percent of the time. Dizygotic twins, or twins that are no more genetically alike than two siblings, more often differed, with 82 percent sharing the same marital status.
Additionally, identical twins were more likely to share personality traits, some of which were found to be associated with marriage.
For example, men who were married scored higher in social potency--the ability to control and profit from social interaction--than did unmarried men. Women who married, however, scored higher on scores of traditionalism and social closeness, and lower on alienation.
The findings suggests that previous studies that correlate being married with positive life outcomes, such as longevity and well-being, might have overlooked genetic influences on marriage and personality. In other words, perhaps those with socially adaptive personalities live longer, and they just happen to get married along the way.
"There might be some tendency for people who are doing better [in life] anyway to be more likely to marry," says Johnson. This may be especially true in American culture, in which marriage is encouraged and even expected, she notes.
Johnson hopes to replicate this study in a country such as Sweden, where marriage is not as normative as it is in the United States. With social pressure lessened, she says, genetic and personality influences on the choice to marry may have an even stronger effect.