Nature, NPR, Wired, et al.

With a few liberating swipes of their paws, a group of research rats freed trapped labmates and raised anew the possibility that empathy isn’t unique to humans and a few extra-smart animals, but is widespread in the animal world. Though more studies are needed on the rats’ motivations, it’s at least plausible they demonstrated “empathically motivated pro-social behavior.” People would generally call that helpfulness, or even kindness.

“Rats help other rats in distress. That means it’s a biological inheritance,” said neurobiologist Peggy Mason of the University of Chicago. “That’s the biological program we have.”

The experiment built on research conducted several years ago by geneticist Jeff Mogil at McGill University, where mice were shown capable of “emotional contagion” — a slightly scary-sounding term denoting a tendency to become upset when cagemates were in pain. This might not seem surprising, but anecdotes from wild animal observations don’t pass academic scrutiny, and it hadn’t before been shown in captive mice. It hinted at unexpectedly sophisticated cognition: Mice were supposed to feel pain, but not each other’s, at least not outside children’s stories.