Evidence of Empathy? Lab Rats Choose Freeing Caged Buddies Before Chocolate Treat

If you thought mammals higher on the phylogenetic tree were the only ones with a little bit of compassion, this study by University of Chicago psychologists will show you otherwise. Researchers found that even lab rats have a sense of empathy, which they will act upon.

Peggy Mason, Jean Decety and Inbal Ben-Ami Bartal at the university put two rats in an enclosure -- one free and one within a cage that could be opened from the outside by a fellow rat.

In repeated tests, rats freed another trapped rat in their cage, even when yummy chocolate served as a tempting distraction. Twenty-three of the 30 rats opened the trap by pushing in a door. The rats could have gobbled the chocolate before freeing their partners, but often didn't, choosing to help and share the goodies.

"Basically they told us (freeing another rat) is as important as eating chocolate," Mason said Mason. "That's a very striking thing."

In some cases, the rats first took the chocolate chips out of a container, but didn't eat them, then freed the other rat and shared "almost as if they were serving them chocolate," Mason said. The research is reported in Thursday's journal Science.

Here's an example:

Wired has more on the research:

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,” Mason said. “That’s the biological program we have.”

Scientists have long studied empathy and emotional connections between animals. Wired reports that Frans de Waal of Emory University, who conducted research the emotional nature of chimpanzees, elephants and dolphins, said this emotional component of the brain must be to some extent within all mammals and "runs deep within us." Wired notes other research where mice became upset when other mice confined with them were upset.

In previous research, Bartal said, according to Wired, that when she conducted surgeries on the mice, the other mice seemed to get anxious. After this, she decided to go to University of Chicago to design a new experiment with Decety and Mason, which resulted in what the women believe shows the rats have empathy but also act upon it when given the opportunity:

Once rats learned to free their trapped and agitated partners, they did so almost immediately in trial after trial. The behavior was clearly deliberate. When the restrainer was empty, rats ignored it. When stuffed rats were restrained, the rats ignored them. “It’s compelling evidence that it’s the distress of the trapped cagemate motivating this helping behavior,” said Mason. “It is a huge leap up to use emotional contagion to actually do something, to actually help another individual.”

To make sure the rats weren’t responding to some immediate social reward — a rat version of a thank-you hug — the researchers tweaked the apparatus so that trapped rats were released into a separate cage. Again, the rats freed each other.

The researchers are reported as saying empathy could be seen in mammals because of the care and nurturing they experience and give to their young. Social settings, such as living in groups, may also make empathy an advantageous trait.

From here, Wired reports that the researchers plan to conduct experiments to see if only the sensation of the other animal's distress is what is causing the free rat to open the door, or if it is truly empathy.

The Associated Press contributed to this report.