A new article, published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), theorizes about the biological source of monogamy.  Researchers note that there are few mammalian species that demonstrate monogamous relationships because it can be costly for reproducing.  This study found that a hormone called oxytocin could be the neurobiological explanation.  Researchers postulate that oxytocin may contribute to romantic bonds in men by enhancing their partner’s attractiveness and reward value compared with other women.

According to My Fox Philly in an analysis of the study, this so-called “cuddle hormone” may be the secret for someone to look more attractive in the eyes of another person that loves him or her.  This hormone is released primarily through physical touch, especially when people hug or kiss, and researchers think it’s the key to monogamy.  Researchers found that this hormone did not have the same effect with colleagues or strangers.

Psychology Today describes oxytocin as a powerful hormone. When individuals hug or kiss a loved one, oxytocin levels in the body increase.  The hormone also acts as a neurotransmitter in the brain.  In fact, the hormone plays a huge role in bonding between pairs of animals. Prairie voles, thought to be one of nature’s most monogamous species, produce large quantities of oxytocin. This hormone is also greatly stimulated during sex, birth, breast feeding, and a number of other activities involving close contact with loved ones.

Another analysis of the study, published in Medical News Today, states that oxytocin has drug-like effects.  Specifically, when an individual takes drugs, he or she is seeking a certain “high” or reward in the brain.  Oxytocin provides such a reward.  However, oxytocin has a selective reward effect, only activating with loved ones as opposed to someone the study subject was just familiar with.  This study only examined males, but other studies have indicated that oxytocin has a drastically different effect on the female brain.

Oxytocin also has a number of other effects.  Another study in PNAS examined how oxytocin triggers protective responses.  One negative impact of oxytocin is its inhibition of amygdala activity, which can be concerning in certain social situations.  This research found that, despite the inhibition, adverse information was still met with a protective response rather than an uninhibited and potentially illogical response.  To achieve that effect, oxytocin may also be affecting memory recall, functional coupling of other brain activities, and emotional modulation.  Together, these result in a protective response to social stimuli.