Rats Will Free Trapped Companions Over Eating Chocolate

The capacity for empathy was long considered a sophisticated trait reserved for humans and our closest primate (Review) relatives. A landmark 2011 study from the University of Chicago, however, dramatically challenged this view by placing lab rats in a difficult social dilemma. A free-roaming rat was put in an arena with two small enclosures: one containing a trapped and distressed cagemate, and another holding a tempting pile of chocolate chips. The free rat, which quickly learned how to open the enclosures, was then faced with a choice between immediate self-gratification and helping another in need.

Overwhelmingly, the rats chose compassion over candy. They consistently opened the enclosure to free their companion before turning their attention to the chocolate, even when they could have easily eaten the treat first and then freed the other rat. This act of prioritizing another's well-being is a powerful form of prosocial behavior. The researchers noted that the helping was likely driven by a form of empathy known as emotional contagion, where the free rat essentially "catches" the anxiety of its trapped peer, motivating it to act.

In a final, remarkable display of altruism, many of the rescuer rats would even save a piece of the chocolate to share with their newly liberated friend. This extra step went beyond simply alleviating another's distress and moved into the realm of active sharing. The groundbreaking experiment suggested the biological roots of kindness and empathy run far deeper and are more widespread in the animal kingdom than we ever imagined.