Summary: Although most commonly associated with promoting aggressive behaviors, testosterone can also promote social affection and prosocial behaviors in men, according to a new gerbil study.
Source: Emory University
Testosterone may encourage friendly, prosocial behavior in men, according to a new animal study. Proceedings of the Royal Society B published research on Mongolian gerbils by neuroscientists at Emory University.
“For what we believe is the first time, we have shown that testosterone can directly promote prosocial, nonsexual behavior, in addition to aggression, in the same individual,” says Aubrey Kelly, an assistant professor of psychology at Emory and first author of the study. .
“It’s surprising because we normally 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.”
The work also revealed how testosterone influences the neuronal activity of oxytocin cells, the so-called “love hormone” associated with social bonding.
Richmond Thompson, a neuroscientist at Oxford College of Emory University, is a co-author of the study.
Kelly’s lab has recently focused on the neural effects of oxytocin using experimental rodent models. Thompson’s lab investigates the neural effects of steroids in fish. Both scientists are trying to solve the question of how hormones work in the brain to allow an animal to rapidly change its behavior, depending on the social context.
In addition to sharing this research interest, Kelly and Thompson share a home as a married couple.
“The idea for this article came from us talking together over a glass of wine,” says Kelly. “Bringing our two worlds of research together.”
Most human studies show that testosterone improves aggressive behavior. Kelly and Thompson wondered whether testosterone might, while increasing aggression toward intruders, also dampen prosocial behaviors.
However, they also hypothesized that it might do something more radical, actually enhance positive social responses in contexts where acting prosocially is appropriate.
To test this question, the Kelly lab conducted experiments with Mongolian gerbils, rodents that form long-lasting pair bonds and raise their young together. Although males can become aggressive during mating and in defense of their territory, they also display hugging behavior after a female becomes pregnant and show protective behavior towards their young.
In one experiment, a male gerbil was introduced to a female. After they formed a pair bond and the female became pregnant, the males displayed the usual cuddling behaviors towards their mates.
The researchers then gave the male subjects an injection of testosterone. They expected that the resulting sharp increase in a male’s testosterone level would decrease his hugging behaviors if testosterone generally acts as an antisocial molecule.
“Instead, we were surprised that a male gerbil became even more affectionate and prosocial with his partner,” says Kelly. “He became a ‘super partner’.”
In a follow-up experiment a week later, the researchers conducted a resident intruder test. Females were removed from their cages so that each male gerbil that had previously received a testosterone injection was alone in its home cage. An unfamiliar male was then introduced into the cage.
“Normally, a male would chase another male that entered his cage or try to avoid it,” says Kelly. “In contrast, resident males who had previously been injected with testosterone were friendlier to the intruder.”
However, the friendly behavior changed abruptly when the original men received another injection of testosterone. They then began to display normal pursuit and/or avoidance behaviors with the intruder.
“It was like they suddenly woke up and realized they didn’t have to be nice in this context,” says Kelly.
The researchers theorize that because the male subjects experienced an increase in testosterone while they were with their partners, it not only rapidly increased positive social responses toward them, but also primed the men to act more prosocially. in the future, even when the context changed and they were in the presence of another male.
However, the second injection of testosterone quickly prompted them to change their behavior to become more aggressive, in the context of a male intruder.
“Testosterone appears to enhance context-appropriate behavior,” says Kelly. “It seems to play a role in amplifying the tendency to be cuddly and protective or aggressive.”
The laboratory experiments, in a sense, slowed down what males could experience almost simultaneously in the wild. In their natural habitat, Kelly explains, mating with a partner raises testosterone, which prepares them to act affectionately in the moment and in the near future while living with their partner, even if levels of testosterone decrease.
If a rival entered her den, the gerbil would likely experience another surge of testosterone that would immediately help her adjust her behavior so she could fend off the rival and protect her young. Testosterone then appears to help animals quickly 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 men who received testosterone injections showed more oxytocin activity in the brain during interactions with a partner compared to men who did not receive the injections.
“We know that the oxytocin and testosterone systems overlap in the brain, but we don’t really understand why,” says Kelly. “Taken together, our results suggest that one reason for this overlap may be that they can work together to promote prosocial behavior.”
Rather than activating an on or off button to modulate behaviors, hormones appear to play a more nuanced role, Kelly says. “It’s like a complicated dashboard where one dial may have to move up a little while another dial moves down.”
Human behaviors are much more complex than those of Mongolian gerbils, but the researchers hope their findings will provide a basis for complementary studies in other species, including humans.
“Our hormones are the same, and the parts of the brain they act on are even the same,” says Thompson.
“Therefore, learning how hormones like testosterone help other animals adapt to rapidly changing social contexts will not only help us understand females and the biological cogs that affect their behavior, but also help us predict and, finally, to understand how the very molecules of the human brain help shape our responses to the social world around us.”
Jose Gonzalez Abreu, a former research specialist in the Kelly lab, is a co-author of the study.
Funding: The work was supported by the National Science Foundation.
About this social neuroscience research news
Author: Carol Clark
Source: Emory University
Contact: Carol Clark – Emory University
Image: Image credited to Aubrey Kelly
Original Research: Closed access
“Beyond Sex and Aggression: Testosterone Rapidly Adapts Behavioral Responses to Social Context and Attempts to Predict the Future” by Aubrey Kelly et al. Proceedings of the Royal Society B
Beyond sex and aggression: Testosterone rapidly matches behavioral responses to social context and attempts to predict the future
Although androgens are widely studied in the context of aggression, androgenic influences on prosocial behaviors have been less explored.
We examined the influence of testosterone (T) on prosocial and aggressive responses in a positively valenced social context (interacting with a mate) and a negatively valenced context (interacting with an intruder) in socially monogamous monogamous gerbils.
T increased and decreased prosocial responses in the same individuals to a conspecific and an intruder, respectively, both within 30 min, but did not affect aggression. T also had persistent effects on prosocial behavior; males in which T initially increased prosocial responses toward a partner continued to show elevated prosocial responses toward a male intruder days later until a second injection of T rapidly eliminated these responses.
Thus, increases in T can rapidly match behavior to the current social context, as well as prime animals for positive social interactions in the future. Neuroanatomically, T rapidly increased cellular responses of hypothalamic oxytocin, but not vasopressin, during interactions with a partner.
Taken together, our results indicate that T can facilitate and inhibit prosocial behaviors depending on the social context, that it can influence prosocial responses on both rapid and prolonged time scales, and that it affects the oxytocin signaling mechanisms that might mediate its behavioral influences depending on the context.
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