Empathy is a quintessential human trait—when we see our friends and neighbors sad or hurt, we give them hugs. Except that humans are not the only animals that show signs of empathy. According to a new study, prairie voles console each other in times of need, more or less like humans do—a finding that could lead to a better understanding of human empathy down the road.
Biologists have actually known for several decades that humans aren't the only animals that care about each other. In 1979, researchers discovered that chimpanzees console each other after being attacked and even reconcile with their attackers through hugs, kisses, and holding hands. Dogs do much the same thing, as do elephants and ravens. Those are all relatively intelligent species, however, hinting that empathy requires a certain degree of cognitive sophistication.
Empathy doesn't require a very sophisticated brain.
The question is, what underlies empathy—consolation in particular—and could it be something more basic than biologists had previously thought?
To find out, James Burkett, a neuroscience graduate student at Emory University, and his colleagues turned to Microtus ochrogaster, better known as the prairie vole, a relative of the common rat and not an especially sophisticated creature. (Kinda cute, though.) Burkett and his team took several dozen voles and paired them up in side-by-side cages. One, the "demonstrator," was first separated from the other, called the "observer." Then, the demonstrator was either left alone for a while or subjected to mild electrical shocks to the feet for half a second—sort of like putting a nine-volt battery on your tongue—five times over the course of 24 minutes.
After being reunited, observer voles spent a lot more time licking and grooming their demonstrator partners when they'd been shocked than when they'd simply been separated—about four times as much, in fact, for a total of about 40 seconds on average over the course of 10 minutes, compared with 10 seconds when the demonstrator rat hadn't been electrically shocked. Observers also reserved their attention for upset mates and siblings, but not strangers. The researchers also found they could turn consolation behaviors off by injecting voles with a drug to suppress oxytocin, the so-called "love hormone" that, among many other things, plays a role in regulating social behavior and emotions.
Taken together, the researchers argue, the results mean that empathy and consoling don't require a very sophisticated brain—though exactly what they do require remains unclear. "[T]he confirmed absence of consolation in the closely related meadow vole and in most macaques [a socially adept monkey species] shows that consolation behavior emerges only under particular social and evolutionary conditions," the researchers write. "Understanding the neurobiology of oxytocin-dependent consolation behavior in prairie voles may help us to understand the diverse deficits in detecting and responding to the emotions of others that are present in many psychiatric conditions, including autism, schizophrenia, and psychopathy."
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