“Using fiber photometry, immunohistochemistry, calcium imaging and other diagnostic tools, researchers found that all the rats they studied experienced empathy in response to another rat’s signs of distress.

However, to act on that empathy, the helper rat’s neural reward circuitry had to be triggered, and that only occurred if the trapped rat was of the same type as the helper rat, or member of its ingroup.

“Surprisingly, we found that the network associated with empathy is activated when you see a distressed peer, whether they are in the ingroup or not,” Kaufer said. “In contrast, the network associated with reward signaling was active only for ingroup members and correlated with helping behavior.””