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American Association for the Advancement of Science

Honor among rats

The presence of a rat trapped in a restrainer elicits focused activity from his cagemate, leading eventually to door-opening and consequent liberation of the trapped rat.
[Image Science/AAAS]

In an unusual example of empathy in animals other than primates, new research shows that rats will liberate their distressed cagemates from a trap, even when they get no additional reward.

These animals seem to be showing empathy, which has often been considered unique to primates. An empathetic animal can "put itself in another's shoes" while maintaining its own perspective and emotional separation.

Inbal Ben-Ami Bartal of the University of Chicago and colleagues now report that after several training sessions, most rats learned to quickly open a container holding a fellow cagemate. The fact that the rats were able to release their cagemates indicates that they recognized the distress of the other rat, but were able to maintain enough calm to open the cage, rather than just freeze or run around.

The rats didn't open containers that were empty or that contained other objects, but they did free other rats even when they weren't allowed to socialize with them afterwards, which is a reward for rats.

And, when the free rats had access to a handful of chocolate chips, which they could have eaten by themselves, they still freed their trapped cagemates and shared the chocolate with them.

This research appears in the 9 December 2011 issue of the journal Science.