Study says testosterone makes males want to cuddle more

By Danny Halpin via SWNS

Testosterone makes males cuddle more - as well as stoking aggression, according to a new study.

American scientists injecting Mongolian gerbils with the hormone found it made them cuddle more with their female partners and act friendlier towards other male intruders.

Study lead author Professor Aubrey Kelly, of Emory University, said: “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 show that it can have more nuanced effects, depending on the social context.”

The study, published in the journal Proceedings of the Royal Society B, also revealed how testosterone affects oxytocin cells – the so-called love hormone that is associated with social bonding.

Kelly and her fellow neuroscientist husband Professor Richard Thompson thought up the study over a glass of wine.

They wondered if testosterone might inspire more prosocial behavior in contexts where that is an appropriate response.

To test the theory, Kelly used Mongolian gerbils, which form lasting bonds and raise pups together.

Males can become aggressive during mating and while defending their territory but they also cuddle with their female partners when they become pregnant and are protective of their pups.

One experiment introduced a male and female gerbil and after they had bonded, the males showed the usual behavior of cuddling.

The researchers then injected the male with testosterone, expecting that it would become less cuddly.

Kelly said: “Instead, we were surprised that a male gerbil became even more cuddly and prosocial with his partner. He became like a super partner.”

A week later, the researchers put intruder male gerbils into a cage with lone males who had been injected with testosterone.

Instead of chasing or avoiding it, the resident males were more friendly towards the intruder.

This changed however after a further dose of testosterone and the resident males resumed their normal behavior.

Kelly added: “It was like they suddenly woke up and realized they weren’t supposed to be friendly in that context.”

The researchers theorized that because the male gerbils had a surge of testosterone while they were with their partners, that positive effect carried over and also made them more sociable towards the intruder.

However, the second dose flipped their behavior back and they became more aggressive as normal.

Kelly said: “It appears that testosterone enhances context-appropriate behaviour. It seems to play a role in amplifying the tendency to be cuddly and protective or aggressive.”

She added that the lab experiments slowed down what the males might experience almost simultaneously in the wild.

In their natural habitat, mating with a partner elevates testosterone which makes them act cuddly and in the near future, even if the testosterone levels drop.

If a rival entered the burrow the gerbil would likely experience another surge of testosterone that would immediately help adjust its behavior so it can fend off the rival and protect its pups.

Therefore testosterone appears to help animals pivot between prosocial and antisocial reactions.

The results of the current study also showed how male gerbils that received testosterone injections showed more oxytocin activity in the brain when with their partner compared to males that did not have the injection.

Kelly said: “We know that systems of oxytocin and testosterone overlap in the brain but we don’t really understand why.

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

She also said that rather than flipping a switch, hormones play a more nuanced role, “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 Mongolian gerbils but the researchers hope their work could boost our knowledge of biology in other species, including humans.

Co-author Professor Thompson added: “Our hormones are the same and the parts of the brain they act upon are even the same.

“So, learning how hormones like testosterone help other animals adjust to rapidly changing social contexts will not only help us understand the biological nuts and bolts that affect their behaviour, but also predict and ultimately understand how the same molecules in human brains help shape our own responses to the social world around us.”