However, they also hypothesized that it might do something more radical, actually enhance positive social responses in contexts in which acting prosocially is appropriate.

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To test this question, they conducted experiments on Mongolian gerbils, rodents that form lasting pair bonds and raise their pups together. While males can become aggressive during mating and in defense of their territory, they also exhibit cuddling behavior after a female becomes pregnant, and they demonstrate protective behavior toward their pups.

In one experiment, a male gerbil was introduced to a female gerbil. After they formed a pair bond and the female became pregnant, the males displayed the usual cuddling behaviors toward their partners.

Testosterone Makes You a Lovable Partner

Researchers then gave the male subjects an injection of testosterone. They expected that the resulting acute rise in a male’s testosterone level would lessen his cuddling behaviors if testosterone generally acts as an antisocial molecule.

Instead, they were surprised that a male gerbil became even more cuddly and prosocial with his partner. In a follow-up experiment a week later, they conducted a resident-intruder test.

The females were removed from the cages so that each male gerbil that had previously received a testosterone injection was alone in his home cage. An unknown male was then introduced into the cage.

Normally, a male would chase another male that came into its cage or try to avoid it. Instead, the resident males that had previously been injected with testosterone were more friendly to the intruder.

The friendly behavior abruptly changed, however, when the original male subjects were given another injection of testosterone. They then began exhibiting normal chasing and/or avoidance behaviors with the intruder.

The researchers theorize that because the male subjects experienced a surge in testosterone while they were with their partners, it not only rapidly increased positive social responses toward them but also primed the males to act more prosocially in the future, even when the context changed and they were in the presence of another male.

However, the second testosterone injection then rapidly prompted them to switch their behavior to become more aggressive, as appropriate to the context of a male intruder. It appears that testosterone enhances context-appropriate behavior.

Testosterone Modulates Behavior In a Delicate Way

The laboratory experiments, in a sense, slowed down what the males might experience almost simultaneously in the wild. In their natural habitat, mating with a partner elevates testosterone, which primes them to act cuddly in the moment and the near future while living with their partner, even if the testosterone levels decline.

If a rival entered its burrow the gerbil would likely experience another surge of testosterone that would immediately help adjust his behavior so he can fend off the rival and protect his pups. Testosterone then appears to help animals rapidly pivot between prosocial and antisocial responses as the social world changes.

The current study also looked at how testosterone and oxytocin interact biologically. The results showed that the male subjects receiving injections of testosterone exhibited more oxytocin activity in their brains during interactions with a partner compared to males that did not receive the injections.

Taken together, the study results suggest that one of the reasons for this overlap may be so they can work together to promote prosocial behavior.

Rather than just flipping an “on” or “off” button to modulate behaviors, hormones seem to play a more nuanced role. It is like a complicated dashboard where one dial may need to move up a bit while another one moves down.

Human behaviors are far more complex than those of Mongolian gerbils, but the researchers hope that their findings provide a basis for complementary studies on other species, including humans.

Source: Medindia