Rats, like humans, will show kindness to strangers, but only if the rats in distress are of a familiar type, a new study has found.

Neurobiologists from the University of Chicago have discovered that rats display empathy-like behavior toward other rats, but the basis of that empathy is environmental, rather than genetic. The creatures aren’t born with an innate motivation to help rats of their own kind, but instead those with whom they are socially familiar.

“Rats choose to help according to which rats they’ve had a positive social experience with in the past,” said study author and postdoctoral researcher Inbal Ben-Ami Bartal.

As part of what Bartal calls the “Mowgli experiment” — a reference to the boy raised by wolves in Rudyard Kipling’s “The Jungle Book” — researchers plucked albino pups from their mothers on the day they were born and transferred them to a group of black-patched rats. As adults, the albinos refused to help other albinos but readily freed black-patched rats.

“There’s no mirror in nature,” said study author and neurobiologist Peggy Mason. “They are not born with an idea of who they are, and therefore, who they should help.”

Scientists watch as rats take part in a study of empathy at the University of Chicago. (Kevin Jiang/University of Chicago)

The study was published online Tuesday in the journal eLife.

The researchers said empathic behavior is common in the natural world. “Helping and empathy are evolutionary advantages,” Mason said. “If Mom doesn’t know how her pups feel, the pups die — and that’s not going to work evolutionarily.”

In social animals, including humans, empathy starts with the mother-child bond but develops to include a peer network. And though rat empathy is not the same as human empathy, the basis is the same: We are upset by another individual’s distress.

“That’s the building block of the empathic response,” Bartal said. “When we help end the distress of that person, it relieves the distress in ourselves.”

In an experiment, researchers trapped one rat inside an uncomfortable, coffinlike restrainer with a door that could only be opened by a free-roaming rat. The jailed rodent squirmed inside its clear plastic cell, showing signs of distress.

The researchers’ first study of rat empathy found that albino rats, raised with other albino rats, formed a strong enough bond within two weeks to help each other. After that study, scientists began asking what would happen if an albino rat saw a trapped albino rat that was a stranger.

“The prediction was that they wouldn’t be so helpful toward strangers, but they were exactly as nice to the strangers as they were to the cage mates,” Bartal said.

Then they wondered whether an albino rat wouldn’t be as nice to rats of a different strain: Long-Evans rats, which are white with a cape of black fur.

The researchers found that a free albino rat would help a trapped Long-Evans rat, even one it had never met before, if it had lived with one in the past. Otherwise, it would not free the struggling creature. Familiarity appeared to override a natural social bias against a foreign strain, but was that bias ingrained from birth?

Their Mowgli experiment proved it wasn’t: There was no innate basis for the rats to only help their own strain. Only by seeing family and siblings, or friends living in the same cage, do the rodents determine who is worthy of empathy.

It is tempting to expand the findings to humans, particularly to issues of race, for example. But Mason says races are different than strains because there’s even less of a genetic barrier between races.

Race is “actually not biological. It’s cultural. There’s far more genetic variation within populations than between populations,” she said. “Certainly in America, what we call a different race is hugely a cultural construct.”

Still, Bartal said, there’s an obvious takeaway: “It does suggest that a diverse social environment does wonders for expanding helping behaviors toward others who are not similar to yourself.”

Kim is a freelance science journalist based in Philadelphia.