Consoling someone you know while they’re upset might seem like second nature to you, but how common is it in nature? Perhaps more so than we thought, as a new study has shown that the highly sociable prairie vole shows this empathy-based behavior when others are distressed. Like humans, it seems that our favorite “cuddle chemical,” oxytocin, has a big part to play.
More than just showing us that consolation could be more widespread in the animal kingdom than believed, the research is important because it demonstrates that, contrary to popular belief, advanced cognitive capacities may not be a prerequisite for this response.
“Consolation has been seen in great apes such as chimps and a few other species, but we always thought that high levels of cognition were needed to have this behavior,” study author Elissar Andari from Emory University told IFLScience. “Our most important point is that we have now shown, for the first time, consolation in animals with a small brain. This shows the response could be emotionally based, and doesn’t necessarily require cognitive aptitude.”
Prairie voles were chosen as subjects for the study, published in Science, due to their exceptionally social nature, which separates them from more traditional lab models. Unlike many mammals, they share parental duties and form enduring, monogamous bonds with mates. Interestingly, their close relative, the meadow vole, is both promiscuous and asocial.
Elephants are among the few species that have shown consolation behaviors. Africa Wildlife/Shutterstock
To find out whether prairie voles also show empathy-motivated behaviors, Emory researchers set up an experiment in which they temporarily isolated either known individuals, including relatives and mates, or strangers using a transparent barrier. One of the pair, the “demonstrator,” was then either left alone or exposed to a stressor, a small foot shock delivered alongside a noise.
If the pair knew one another, during the stressful experience the observer began mirroring the demonstrator’s anxiety-like behavior, increasing self-grooming. And when they were reunited, the observer spent significantly longer grooming the demonstrator that had been shocked, compared to the control that was not stressed. In contrast, strangers did not show this response, and neither did meadow voles.
As anticipated with conditioning experiments, when the noise was played but without the shock, the demonstrator showed a fear and anxiety response by freezing. But interestingly, in familiar pairs the observer also froze, which Andari says is the “first demonstration of emotional contagion behavior” in these animals. As further evidence of this, observers also matched the physiological responses of stressed demonstrators, producing similarly elevated levels of the stress molecule corticosterone.
As the hormone oxytocin is strongly linked with empathy and bonding in humans, the researchers repeated the experiment after pharmacologically blocking the oxytocin receptor in the observers’ brain, and this time no grooming responses were seen. Further indicating a role for oxytocin, prior work has shown that meadow voles and prairie voles have different oxytocin receptor distributions in the brain, Andari says, with the former showing “significantly fewer in key emotional brain regions.” And when they looked at observer brain activity of the anterior cingulate cortex, a known emotional brain region in human empathy, it showed increased activity when familiar prairie voles were seen in distress. In addition, specifically blocking oxytocin receptors in this region once again abolished consoling behaviors in these animals.
Moving forward, the authors believe this information could further our understanding of certain neuropsychiatric disorders, such as autism, where emotional and social development are disturbed.
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