November 26, 2013
Oxytocin Makes Men More Attracted To Their Partners
April Flowers for redOrbit.com - Your Universe Online
A biological mechanism has been discovered that could explain the attraction between loving couples. Researchers at the Bonn University Medical Center found that if oxytocin is administered to men and if they are shown pictures of their partner, the bonding hormone stimulates the reward center in the brain, increasing the attractiveness of the partner, and strengthening monogamy.
Among mammals, monogamy is not very widespread; humans are one of the few exceptions. Compared to other mammalian species, many Homo sapiens couples have no other partners in a love relationship. Science has been trying to understand, therefore, the unknown forces that cause loving couples to remain faithful.
"An important role in partner bonding is played by the hormone oxytocin, which is secreted in the brain," says Prof. René Hurlemann, MSc, MD, PhD, Executive Senior Physician at the Inpatient and Outpatient Department of Psychiatry and Psychotherapy of the Bonn University Medical Center.
Dr. Hurlemann led an international team of researchers, including members from Ruhr University of Bochum and the University of Chengdu (China), which examined the effect of the "bonding hormone" more precisely. Their findings were published in a recent issue of the Proceedings of the National Academy of Sciences (PNAS).
Forty heterosexual men who were in permanent relationships were shown pictures of their female partners, as well as pictures of other women for comparison. The participants were first given a dose of oxytocin in a nasal spray. At a later date, they were given a placebo. The research team studied the brain activity of the subjects as well, with the help of functional magnetic resonance (fMRI) tomography.
"When the men received oxytocin instead of the placebo, the reward system in their brains when viewing the partner was very active, and they perceived them as more attractive than the other women," says psychologist Dirk Scheele, of the University of Bonn, who is lead author of the study.
In a second series of assessments, the research team tested whether oxytocin enhances the activation of the reward system only when seeing the partner or whether there is a similar effect with pictures of acquaintances and female work colleagues of many years.
"The activation of the reward system with the aid of oxytocin had a very selective effect with the pictures of the partners," says Scheele. "We did not detect this effect with pictures of longstanding acquaintances." Simple familiarity, therefore, is not enough to stimulate the bonding effect, the researchers found. The scientists are convinced that the reaction depends on loving couples.
The findings indicated that oxytocin activates the reward system, thus maintaining the bond between the lovers and promoting monogamy. "This biological mechanism in a couple relationship [sic] is very similar to a drug", says Prof. Hurlemann.
People are striving to stimulate the reward system in the brain, both in love and in taking drugs.
"This could also explain why people fall into depression or deep mourning after a separation from their partner: Due to the lack of oxytocin secretion, the reward system is understimulated, and is more or less in a withdrawal state," says Prof. Hurlemann.
The team says that therapy with the bonding hormone could be counterproductive, however. The administration of oxytocin could possibly increase the suffering, as it would make the longing for the missing partner even greater.
Monogamy does not make much sense at first glance as men have an advantage when they disseminate their genes as widely as possible through many different partners from a classical view of evolutionary biology.
The team, however, found another aspect that plays a significant role.
"When oxytocin strengthens the partner bond, it increases the stability of the persons providing nutrition and thus the chances of survival for the progeny," explains Prof. Hurlemann. And children provide a further dissemination of an individual's genes.