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It’s definitely bizarre to think about. Testosterone is the hormone that promotes aggression and extreme masculinity, right? Partly. It’s more like...testosterone helps males to quickly adapt and switch their behaviors between prosocial and antisocial depending on the scenario they find themselves in, according to recent scientific research on the sex hormone and behavior. The findings were published in the Proceedings of the Royal Society B journal and conducted by researchers at Emory University. They concluded that testosterone, the male sex hormone, can cause men to be more sociable and more friendly toward others.

Aubrey Kelly, one of the authors, says, “For what we believe is the first time, we’ve demonstrated that testosterone can directly promote nonsexual, prosocial behavior, in addition to aggression, in the same individual. It’s surprising because normally we think of testosterone as increasing sexual behaviors and aggression. But we’ve shown that it can have more nuanced effects, depending on the social context.”

Testosterone Can Affect the Production of Oxytocin

The love hormone, oxytocin, was also found to have a connection to testosterone, with testosterone affecting the activity of oxytocin cells. Oxytocin is usually associated with sexual and romantic bonding, as well as the bonding between mother and child after birth. The authors of the study were trying to better understand how different hormones function in the brain, using animal models for now, in order to help an animal to change its behavior based on the social situation it finds itself in.

Most people think that testosterone promotes aggressive behavior, and they aren’t wrong. The research also supports this as well. But study authors were questioning whether testosterone could also increase prosocial behaviors, instead of just increasing antisocial ones, such as hostility. They believed that the sex hormone could possibly boost positive social reactions in situations where this would be socially appropriate.

The animal models used were Mongolian gerbils. These rodents actually create long-lasting mated pairs and raise their young together, similar to humans. The male gerbils do become more violent during the mating season and will defend their territory, but they will also cuddle their females and display protective behavior toward the young once the female gerbil is pregnant. Who knew we had so much in common with gerbils? We are related after all…

Testosterone Injection Produced More Cuddling Behavior

Now for the experiments. A male and female gerbil were introduced to each other. They developed a pair bond and the female got pregnant. Awww. Once this happened, the male became cuddlier toward the female. Next, the males were given testosterone injections. The researchers thought that this would reduce the cuddling behaviors by the males, however, “Instead, we were surprised that a male gerbil became even more cuddly and prosocial with his partner. He became like ‘super partner.’”

A week later, the scientists performed something they called the “resident-intruder test.” The males who had been given a testosterone injection the previous week said bye-bye to their females, who were taken from the cage. He was now alone. Next, an unknown male was put in the cage. You would think that the original male would get mad and try to chase the intruder out, biting and fighting with it. “Instead, the resident males that had previously been injected with testosterone were more friendly to the intruder.” Surprise, surprise!

Testosterone Enhances Context-Appropriate Social Behavior

This more cordial behavior was quickly switched back to aggressiveness when the resident males were given another injection of testosterone. Kelly says, “It was like they suddenly woke up and realized they weren’t supposed to be friendly in that context.”

The scientists believe that the surge of testosterone in the males when with their female partners rapidly increased the more prosocial and positive social reactions since that was what the context called for at the time, while also priming them to act more prosocially in the near future, even when the context of the social situation changed (the introduction of the male and removal of their mate). With the second injection of testosterone and subsequent surge, this prompted them to act more “appropriately” towards the given social situation – getting the male intruder out and being aggressive/antisocial.

Kelly says, “It appears that testosterone enhances context-appropriate behavior. It seems to play a role in amplifying the tendency to be cuddly and protective or aggressive.” The hormone assists the animals in rapidly switching between prosocial and antisocial responses as the environment changes around them. It’s likely that in the wild, the gerbil would experience a surge of testosterone when another male gerbil would enter his territory.

In terms of their findings involving oxytocin, they found that the male gerbils injected with testosterone also exhibited higher oxytocin activity in the brain during their time with the female when compared to the males who were not injected.

Kelly says, “Our results suggest that one of the reasons for this overlap [testosterone and oxytocin activity in the brain] may be so they can work together to promote prosocial behavior.”