New research published online May 15 has discovered that prenatal testosterone levels influence how adults react to infidelity.
“Confrontational and violent reactions to infidelity have been observed throughout history, across cultures, and among a variety of species,” Jon K. Maner of Florida State University and his colleagues wrote in their study, which was published in Social Psychological and Personality Science. “The current findings offer novel insight into a physiological mechanism potentially underlying confrontational responses to infidelity.”
Maner and his colleagues found men and women exposed to higher levels of prenatal testosterone were more likely to approach potential romantic rivals. The study involved 58 undergraduate students who were asked to imagine their romantic partner flirting with another person and then completed a computerized task to measure their willingness to approach or avoid various people.
Exposure to testosterone in the uterus has been found to lead to permanent changes in brain structure. Researchers obviously cannot directly measure prenatal testosterone levels in adults. However, the difference between the length of the index finger to the ring finger has been found to be an indicator of prenatal testosterone. This ratio is known as 2D:4D — or second digit to fourth digit.
Those exposed to higher levels of testosterone while in the uterus tend to have a lower 2D:4D. In other words, the shorter a person’s index finger is compared to their ring finger, the more testosterone they were exposed to in the uterus.
“Prenatal testosterone may be associated with confrontational responses to threatening intrasexual rivals as an adaptation to environmental instability,” Maner and his colleagues explained in the study.
Maternal stress has been linked to increases in prenatal testosterone. Researchers believe the effect could be an evolutionary adaptation to prepare offspring for a dangerous environment where mates are rare, sexual competition is fierce, and life is short.
“Environmental instability during early development may incline offspring toward a faster life history strategy, which entails heightened intrasexual competition, aggression, and risk taking,” the researchers added. “High prenatal testosterone may prepare individuals to respond confrontationally to reproductive threats, and this propensity may persist into adulthood.”
The study was co-authored by Saul L. Miller of the University of Kentucky, Jacqueline M. Coyle of Stetson University and Michael P. Kaschak of Florida State University.
