Rats Will Avoid Actions That Hurt Others -- Even If It Earns Them A Treat

A new study has found that rats, like humans, will avoid actions that can cause pain to their fellow beings.

This trait is known as harm aversion.

Researchers believe their findings will help scientists develop new treatments to increase harm aversion in human patients who show psychopathic behavior.

"We share a mechanism that prevents antisocial behaviour with rats, which is extremely exciting to me," says professor Christian Keysers, study group leader at the Netherlands Institute for Neuroscience. "We can now use all the powerful tools of brain science to explore how to increase harm aversion in antisocial patients."

To investigate harm aversion in rats, the researchers gave them a choice between two levers they could press to receive sugary treats.

Once the animals developed a preference for one of the two levers, the scientists reconfigured the system so that pressing their favorite lever would also cause the rat in the next cage to receive an unpleasant shock while the treat was being dispensed. When the fellow rodents reacted by squeaking their protest, the rats stopped using their preferred lever.

"Much like humans, rats actually find it aversive to cause harm to others," said Dr. Julen Hernandez-Lallement, first author of the study and a researcher at the NIN.

The researchers then scanned the brains of rats and found a region of the brain, known as the anterior cingulate cortex, to become active. This same brain region has also been found to light up in people empathising with the pain of others.

"It shows that the moral motivation that keeps us from harming our fellow humans is evolutionary old, deeply ingrained in the biology of our brain and shared with other animals," said Dr. Valeria Gazzola, a senior author of the study.