Do hormones make men choose between love or sex?

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      Everyone has a friend who is a “relationship person”. Happier spending their time with one individual rather than sowing their wild oats, relationship people have had numerous long-term partners, and never seem to be without their companion.

      Promiscuous friends are the opposite. Swiping on dating apps to tap the pool of local singles (pro tip: no one is picking their spouse based on their Tinder photos), sex-driven individuals would rather keep it casual.

      According to a UBC researcher, those behavioral differences might be due to a variation in hormone levels.

      Biologically, searching for sex and looking for love are two different things, says Alec Beall, a postdoctoral researcher in UBC’s department of psychology.

      Love—defined as a feeling of social bonding—is regulated by a hormone named oxytocin in both men and women. Released in the body in response to stimuli like looking into the eyes of a baby, examining photos of vulnerable kittens, or cuddling, the chemical plays an important role in creating strong, committed relationships, both towards a partner or a child.

      In men, testosterone is responsible for regulating the sex drive. Primarily produced in the testes, the hormone at healthy levels plays a role in arousal. While oxytocin is more of a nurturing chemical, testosterone is involved in motivating individuals to pursue casual sex.

      According to Beall, a high sex drive and a desire to nurture are opposing motivations.

      “My [past] dissertation research looked at priming people to feel tenderness, and seeing how it affected their short-term mating drive,” says Beall. “I showed UBC undergraduates pictures of puppies and kittens, and had them think about what it would be like to take care of them. Then they took a survey that assessed their desire to sleep around. What I found was that when people were in this parental caring mindset, they were less likely to report a desire to sleep around. When we primed them with pictures and erotic scenarios to make them think about a short-term mating encounter, they reported lower tenderness responses to pictures of infants. All these motivations are driven by complex underlying physiological components, which is what drove me to the oxytocin study.”

      Beall’s new research will examine whether the reason for those apparently opposing drives—whether to be sexually promiscuous or monogamous towards a partner—are because of oxytocin levels.

      His study will bring 25 men and 25 women into the lab at separate times, and give them a dose of either oxytocin or a placebo via a nasal spray.

      “What we’re expecting is that people under oxytocin will exhibit a weakened desire to sleep around, because the oxytocin temporarily boosts their desire to parent and nurture,” says Beall. “We hope to capture this change in motivation using several methods. First, we’ll use eye-tracking to note whether a participant’s gaze is drawn more to attractive, short-term sexual opportunities, or to human infants, and to the bodies of attractive swimsuit models or to their faces. Next, we are using questionnaires to assess whether participants report a reduced attraction to short-term mating prospects. Finally, we are using saliva tests to determine how much testosterone participants produce in reaction to erotic stimuli. We’re expecting that oxytocin will increase parenting motivation, and we’re using a number of psychological, behavioural, and physiological measures to see what happens with the short-term mating drive.”

      Beall believes that it’s an important evolutionary advantage to have separate hormones for sex and love. Humans have an innate desire to have children, and it’s necessary to acquire a mate to successfully reproduce. In order for those children to survive and pass on that genetic material, however, they have to grow to the age of sexual maturity—which would be more likely with additional adults to look after them.

      “Within evolutionary biology, the mating/parenting trade-off suggests that because we have limited bioenergetic resources, we cannot devote them to both parenting existing offspring, as well as producing a bunch of additional offspring,” he says. “Our bodies make an unconscious decision: we either invest in mating, or we invest in parenting.”

      Kate Wilson is the Technology Editor at the Georgia Straight. Follow her on Twitter @KateWilsonSays