Rats can experience “emotional contagion”: when one rat is distressed, another acts the same way. But can a rat show a more nuanced form of empathy in which it acts to alleviate the suffering of another? To find out, Bartal et al. tested whether rats would rescue a trapped cagemate, without any obvious reward.
The group found that rats would release trapped cagemates from restrainers, but ignored empty restrainers or those containing only a toy rat. In some trials, the rats would free their trapped cagemate before opening a restrainer containing chocolate, a preferred rat treat. In the accompanying video, paper author Peggy Mason narrates several runs of the experiment.