A scientific investigation into human monogamy has found that the hormone oxytocin (OXT) can cause men to perceive their partners as more attractive than other women. When shown an image of their female partner, the reward regions of men’s brains were triggered by the hormone. It is therefore thought that the prevalence of oxytocin in males may increase the likelihood of them remaining faithful.
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Researchers from the University of Bonn in Germany and the University of Electronic Science and Technology of China analysed OXT interaction with brain dopamine reward systems in 40 heterosexual pair-bonded males.
During a controlled MRI experiment, the study found that intranasal OXT treatment made subjects perceive their female partner’s face as more attractive compared with unfamiliar women but had no effect on the attractiveness of other familiar women.
In a separate experiment, they also found that men dosed with oxytocin kept a physical distance from attractive female researchers, while their OXT-free counterparts all stood closer.
“Our results suggest that OXT could contribute to romantic bonds in men by enhancing their partner’s attractiveness and reward value compared,” the report concludes.
Plasma OXT levels can be elevated by several attachment-related experiences, including partner hugs, social support, massages or orgasms. It is thought that the hormone may facilitate the fidelity of men in a monogamous relationship by making them keep a greater distance from other women
The study notes that sexual monogamy is potentially costly for males, and few mammalian species other than humans exhibit it.