Dogs, dolphins and elephants are known to show empathy when a loved one is in pain, and now researchers have found the first consoling behavior in a rodent, known as the prairie vole.
Researchers say the findings, published Thursday in the US journal Science, could help scientists better understand human disorders such as autism and schizophrenia, in which a person's ability to sense the emotions of others is disrupted.
The secret to empathetic behavior lies in the hormone oxytocin, which promotes maternal bonding and feelings of love among humans, too.
Scientists at the Yerkes National Primate Research Center at Emory University created an experiment in which they isolated prairie voles - dark rodents which mate in long-term monogamous pairs and raise their offspring together - from others they knew.
Then they gave one prairie voles a series of mild shocks before returning it to its loved one.
Once reunited, the unaffected rodents swiftly began to lick and groom the fur of the animals that were in distress after the shocks.
They "licked the stressed voles sooner and for longer durations, compared to a control scenario where individuals were separated but neither was exposed to a stressor," said a statement from Emory University.
Consoling behavior was also not seen in prairie voles that were unfamiliar with each other before being separated.
Knowing that in the human brain, the receptor for oxytocin - also known as the love hormone - is associated with empathy, researchers decided to block this neurotransmitter in the brains of some of the animals.
They found that blocking oxytocin caused the animals to stop consoling each other.
"Many complex human traits have their roots in fundamental brain processes that are shared among many other species," said co-author Larry Young, director of the Silvio O. Conte Center for Oxytocin and Social Cognition at Emory University.
Young said his research points to a potential role for oxytocin in the treatment of autism spectrum disorder, though more work is needed.
"We now have the opportunity to explore in detail the neural mechanisms underlying empathetic responses in a laboratory rodent with clear implications for humans."
According to study co-author Frans de Waal, who first discovered animal consolation behavior in chimpanzees in 1979, the findings also shed new light on the range of animals that feel empathy, and how empathy is separate from complex cognition.
"Scientists have been reluctant to attribute empathy to animals, often assuming selfish motives," he said.
"These explanations have never worked well for consolation behavior, however, which is why this study is so important."