Testosterone is often thought to increase sexual urges and aggression in men, but a new study shows it also has a cuddly side.
In experiments, researchers injected testosterone into male gerbils to see how they would behave with their partners.
The injections promoted cuddling and “friendly behavior” and prepared them for “positive social interactions,” they found.
Testosterone affects the activity of oxytocin, the so-called “cuddle” or “love” hormone linked to social bonding, the researchers say, though they don’t know how.
Testosterone affects the activity of oxytocin – the so-called ‘cuddle’ or ‘bonding’ hormone associated with social bonding (file photo)
WHAT IS TESTOSTERONE?
Testosterone is the male sex hormone and is usually made in the testicles, but also in the adrenal glands, which are located near the kidneys.
It causes the voice to deepen, body hair to grow, and the genitals to expand during puberty.
In addition to affecting sex drive and sperm production, it also plays a role in the development of strong bones and muscles and how the body distributes fat.
Women also make small amounts of the hormone in the ovaries and adrenal glands, and it affects their fertility and bones and muscles.
In women, relatively small amounts of testosterone are released into the bloodstream by the ovaries and adrenal glands.
Testosterone and other androgens “play an important role in women’s healthy sexual functioning, especially in stimulating sexual interest and maintaining desire,” according to a study published last year.
“Testosterone initiates sexual activity and spreads sexual desire and behavior,” it says.
“In addition, testosterone is essential in modulating clitoral and vaginal physiology to facilitate genital lubrication, sensation and engorgement.”
The new study was conducted by researchers at Emory University in Atlanta, Georgia, led by assistant professor of psychology Aubrey Kelly and her husband Richmond Thompson, a neuroscientist.
“For what we believe to be the first time, we have shown that testosterone can directly promote non-sexual, prosocial behavior in the same person, in addition to aggression,” she said.
“It’s surprising because we normally think of testosterone as increasing sexual behavior and aggression.
‘But we have shown that it can have more nuanced effects, depending on the social context.’
The study, published in Proceedings of the Royal Society Bconcerned experiments on Mongolian gerbils (Meriones unguiculatus).
Used in scientific experiments since the 1800s, these tiny rodents form durable pair bonds and raise their pups together.
Males can become aggressive when mating and defending their territory, but they also show cuddling behavior after a female has become pregnant, and they show protective behavior towards their pups.
In one experiment, a male gerbil was introduced to a female gerbil. After they mated and the female became pregnant, the males exhibited the usual cuddling with their partners.
The researchers then gave the male subjects an injection of testosterone, assuming that the boost would reduce his cuddling behavior.
“Instead, we were surprised to see a male gerbil become even more cuddly and prosocial with his partner,” Kelly said.
“He became a super partner.”
In a follow-up experiment, the researchers removed females from the cages so that each male gerbil that had previously received a testosterone injection was alone.
An unknown male was then introduced into the cage – raising the possibility that the two rivals might start fighting.
“Normally a male would chase another male that got into his cage, or try to avoid it,” Kelly said.
“Instead, the male residents who had previously been injected with testosterone were kinder to the invader.”
Mongolian gerbils (Meriones unguiculatus, pictured) have been used in scientific experiments since the 1800s
MEN WITH HIGH TESTOSTERONE ‘ARE MORE DONKEY FANS’
Having high levels of testosterone may make men less generous and more likely to engage in selfish behavior, a study finds.
Psychologists from China and Switzerland measured the brain activity of men as they completed a task that required them to choose between generous and selfish options.
Men who were given extra testosterone three hours before completing the task tended to choose the more selfish options, they found.
Testosterone also dampened activity in a brain region known to be involved in the well-being of others.
However, the friendly behavior changed abruptly when the original male subjects were again injected with testosterone.
With the additional injection, the male began to chase or completely avoid the rival male invader.
“It was like they suddenly woke up and realized they weren’t supposed to be friendly in that context,” Kelly said.
Kelly said testosterone “improves context-appropriate behavior” and may play a role in “reinforcing the tendency to be cuddly and protective or aggressive.”
In the wild, testosterone also appears to help animals quickly switch between prosocial and antisocial responses, depending on the context.
The researchers found that men who received injections of testosterone showed more oxytocin activity in their brains during interactions with a partner compared to men who did not receive the injections.
Testosterone probably affects the activity of oxytocin, but the researchers aren’t sure how.
“We know that systems of oxytocin and testosterone overlap in the brain, but we don’t really understand why,” Kelly said.
Taken together, our results suggest that one of the reasons for this overlap may be that they may work together to promote prosocial behavior.
The obvious limitation of the study is that gerbils were used instead of humans, so the results should be applied cautiously to other animals.
Human behavior is much more complex than that of gerbils, but the findings could provide a basis for studies in other species, including humans.
“Our hormones are the same, and the parts of the brain they act on are even the same,” Thompson said.
3D illustration of a testosterone molecule. Testosterone is the male sex hormone and is usually made in the testicles, but also in the adrenal glands, which are located near the kidneys
Previous studies have linked the presence of testosterone to various social or psychological behaviors in men.
Last year, researchers at the University of Bristol found that testosterone does not lead to success in life, which contradicts previous assumptions.
The Bristol experts suggested that high testosterone could be the result of success, rather than the other way around, which could explain previous studies linking high levels of the hormone to a successful life.
Another 2021 study found that having high levels of testosterone can make men less generous and more likely to engage in selfish behavior.