Oxytocin ensures monogamy in men

Researchers from the University of Bonn Medical Center have discovered a biological mechanism that can explain the attraction between loving couples. When men who have been given oxytocin are shown photos of their partners, the hormone stimulates the reward center in the brain, increasing the attractiveness of the partner and increasing the incentive for monogamy.
People are special creatures, at least when it comes to relationships. The intention for a monogamous relationship is something that few other mammals have. When people are in love, they produce the hormone oxytocin. It has recently been discovered that this hormone encourages men to enter into a monogamous relationship. How exactly does this work?

Oxytocin makes the partner more attractive

Researchers showed photos of wives to forty heterosexual men. Photos of random women were also shown for comparison. The men looked at the photos twice. Once they were given oxytocin via a nasal spray, the other time a placebo. The researchers then had the men look at the photos of the women and imaged the brain activity using functional MRI (fMRI).

When the men were given oxytocin, the reward center in the brain became active when they looked at the photo of their wife. This did not happen when they were shown photos of random women or when they were given the placebo. Showing photos of women who had known the men for a long time, such as long-term colleagues or acquaintances, also had no effect on the reward center in the men’s brains. Therefore, it was concluded that a loving relationship was necessary to activate the reward center.

The reward system

Thanks to the activation of the reward system by the hormone oxytocin, monogamy is promoted. The situation of someone in whom the reward system is activated can be compared to someone who has used drugs. This also activates the reward system in the brain. The fact that people want to activate their reward system can also explain why people can get so down after breaking up a relationship. The production of oxytocin then stops, and the reward system in the brain is no longer activated. The symptoms that a person then experiences can be compared to the effects of drug withdrawal.

The evolution

At first glance, it does not seem necessary for men to enter into monogamous relationships; After all, they can spread their seed and produce more offspring if they do not enter into monogamous relationships. The reason that the hormone oxytocin has survived evolution could be that a monogamous relationship increases the stability of the people who provide food, and therefore a greater chance of survival, according to the researchers.