The findings, published today, Tuesday, July 13, in the journal eLife, suggest that altruism, whether in rodents or humans, is motivated by social bonding and familiarity rather than sympathy or guilt.
“We have found that the group identity of the distressed rat dramatically influences the neural response and decision to help, revealing the biological mechanism of ingroup bias,” said study senior author Daniela Kaufer, a professor of neuroscience and integrative biology at UC Berkeley.
With nativism and conflicts between religious, ethnic and racial groups on the rise globally, the results suggest that social integration, rather than segregation, may boost cooperation among humans.
“Priming a common group membership may be a more powerful driver for inducing pro-social motivation than increasing empathy,” said study lead author Inbal Ben-Ami Bartal, an assistant professor of psychobiology at Tel-Aviv University in Israel.
Bartal launched the study in 2014 as a postdoctoral Miller fellow in Kaufer’s laboratory at UC Berkeley. Bartal, Kaufer and UC Berkeley psychology professor Dacher Keltner led a research team that sought to identify the brain networks activated in rats in response to empathy, and whether they are mirrored in humans. The results suggest they are.
“The finding of a similar neural network involved in empathic helping in rats, as in humans, provides new evidence that caring for others is based on a shared neurobiological mechanism across mammals,” Bartal said.
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.”
Specifically, the rats’ empathy correlated with the brain’s sensory and orbitofrontal regions, as well as with the anterior insula. Meanwhile, the rodents’ decision to help was linked to activity in the nucleus accumbens, a reward center with neurotransmitters that include dopamine and serotonin.
Source material from University of California Berkley