Testosterone encourages ‘cuddling’ not only violence; animal study finds

A recent animal research found that testosterone can drive men to be more gregarious and friendly. The findings of Emory University neuroscientists’ study on Mongolian gerbils were published in the Proceedings of the Royal Society B.

“We’ve shown that testosterone may directly enhance nonsexual, prosocial conduct, along with aggression, in the same individual, for what we believe is the first time,” says Aubrey Kelly, an assistant professor of psychology at Emory University and the study’s first author. It’s unexpected because often we associate testosterone with escalating aggressive and sexual activities. However, we’ve demonstrated that, depending on the social environment, it can have more complex impacts. The research also demonstrated how testosterone affects oxytocin cells’ brain activity, the so-called “love hormone” linked to social bonding.

The study’s co-author is Richmond Thompson, a neuroscientist at Oxford College at Emory University.

Using rodent experimental models, Kelly’s lab has recently concentrated on the brain effects of oxytocin. The effects of steroids on fish’s neurological systems are studied by Thompson’s group. Both researchers are attempting to answer the question of how hormones function in the brain to enable an animal to quickly alter its behaviour in response to its social environment.

Kelly and Thompson live together as a married couple and also have a common research interest.

We were conversing over a glass of wine when the concept for this article first came to us, Kelly claims. It combines the two spheres of our research.

Most human research have found that testosterone makes people more violent. Kelly and Thompson questioned if testosterone might also generally reduce prosocial behaviours in addition to its ability to promote hostility toward invaders.

They also speculated that it might have a more drastic effect, enhancing favourable social reactions in situations where doing good deeds is appropriate.

The Kelly lab experimented on Mongolian gerbils, rodents that create enduring pair bonds and raise their young together, to answer this question. Males can be hostile during mating and when defending their territory, but they also engage in snuggling and protective behaviour when a female gets pregnant.

In one experiment, a male and a female gerbil were introduced. The males adopted their customary snuggling behaviours toward their companions once they developed a pair connection and the female got pregnant. The male test volunteers were subsequently given an injection of testosterone by the researchers. They anticipated that since testosterone often has an antisocial effect, the consequent sharp increase in a man’s testosterone level would reduce his tendency to cuddle.

As opposed to that, Kelly notes, “we were startled that a male gerbil became even more affectionate and prosocial with his spouse.” He developed into a “great companion.”

A week later, the researchers ran a resident-intruder test as a follow-up experiment. Each male gerbil who had previously gotten a testosterone injection was left alone in his own cage after the females were taken out of the cages. The cage was then filled with an unidentified guy.

A male would typically try to avoid or chase another male that entered its cage, according to Kelly. Instead, the local males who had previously received testosterone injections were friendlier toward the visitor.

However, when the initial male patients received another injection of testosterone, the friendly behaviour rapidly altered. When the intruder approached, they started displaying typical pursuing and/or avoiding behaviours. According to Kelly, “it was like they all of a sudden realised they weren’t allowed to be nice in that situation.”

According to the researchers, because the male subjects’ testosterone levels spiked while they were with their partners, it not only quickly increased the positive social reactions to them but also primed the males to act more prosocially in the future, even when the context changed and they were around another male. The second testosterone injection, however, quickly caused them to change their behaviour and become more hostile, as befitting a male intruder.

According to Kelly, “it seems that testosterone increases context-appropriate conduct. It appears to contribute to enhancing the propensity for being cuddly, protective, or violent.”

In a sense, the laboratory tests slowed down what males might go through practically simultaneously in the wild. Kelly argues that in their natural environment, mating with a spouse raises testosterone levels, preparing them to behave affectionately in the present and the near future when residing with their partner, even if the testosterone levels fall.

The gerbil would probably suffer another spike in testosterone if a competitor entered its burrow, which would prompt him to instantly alter his behaviour in order to ward off the competitor and save his offspring. As the social environment changes, testosterone then seems to aid animals in quickly switching between prosocial and antisocial behaviours.

The biochemical interactions between oxytocin and testosterone were also examined in the current investigation. The findings demonstrated that, in comparison to men who did not receive testosterone injections, men who did so showed increased oxytocin activity in their brains during interactions with a partner.

Kelly claims that although “we know that oxytocin and testosterone systems cross in the brain, we really don’t understand why.” When seen as a whole, our findings imply that one rationale for this overlap may be so they can cooperate to encourage prosocial behaviour.

Kelly claims that hormones appear to play a more sophisticated role in behaviour modulation compared to simply switching a “on” or “off” switch. “It’s like a convoluted dashboard where one dial might need to move a little up while another one slides down,” the speaker said.

Although human behaviours are much more complex than those of Mongolian gerbils, the researchers believe that their findings will serve as a foundation for more research in humans and other animals.

According to Thompson, the parts of the brain that our hormones activate are even the same. It will be useful to discover how hormones like testosterone assist other animals adjust to quickly changing social circumstances in order to forecast and ultimately comprehend how the same chemicals in human brains help shape our own reactions to the social environment around us. This will aid us in understanding the biological roots of their behaviour.