THE ESSENTIAL
- A second injection of testosterone quickly caused the male rodents to change their behavior and made them more aggressive towards the same-sex intruder.
- Male rodents injected with testosterone showed increased activity of oxytocin, the happiness hormone, in their brains during interactions with their partner.
Testosterone would encourage more hugs! This is what scientists from Emory University in Georgia (USA) recently discovered. To reach this conclusion, they conducted a study, the results of which were published in the journal Proceedings of the Royal Society B Biological Sciences.
Experiments on rodents
As part of this work, researchers looked at the influence of this male sex hormone on relationships and social interactions, as the majority of research shows that testosterone is associated with aggressive behavior. For the purposes of the study, they conducted experiments in a lab on Mongolian gerbils, rodents that form long-lasting pair bonds and raise their offspring together.
More hugs following a spike in testosterone levels
In a first experiment, a male rodent was introduced to a female gerbil. Once they formed a pair and the female became pregnant, male gerbils exhibited affectionate behaviors towards their partners. The authors then injected testosterone into the male rodents. They expected that the increase in testosterone levels would reduce affectionate gestures. “On the contrary, we were surprised to find that the males hugged their partners even more,” said Aubrey Kelly, author of the work, in a statement.
Friendly behavior with a rodent of the same sex
In a second experiment, conducted a week later, the team removed the female gerbils from the cages so that each male rodent injected with testosterone was left alone. The scientists then placed another male rodent in the cage. “Normally, a male would chase another male who enters his cage, or try to avoid him. Instead, the male already present, who had been injected with testosterone, was friendlier to the intruder,” specified the researcher.
“Testosterone helps to adapt to social contexts”
The behaviors of humans are far more complex than those of Mongolian gerbils, but the authors hope their findings will allow for further studies in other species, including humans.
“Our hormones are the same, and the parts of the brain they act on are even the same. So learning how testosterone helps animals adapt to rapidly changing social contexts will not only help us understand the biological workings that affect their behavior, but also to predict and ultimately understand how the same molecules in the human brain help shape our own responses to the social world around us.” said Richmond R. Thompson, co-author of the research.
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