Bartal, I. B. A., Decety, J., & Mason, P. (2011). Empathy and pro-social behavior in rats. Science, 334(6061), 1427-1430.
Whereas human pro-social behavior is often driven by empathic concern for another, it is unclear whether nonprimate mammals experience a similar motivational state. To test for empathically motivated pro-social behavior in rodents, we placed a free rat in an arena with a cagemate trapped in a restrainer. After several sessions, the free rat learned to intentionally and quickly open the restrainer and free the cagemate. ...