It seems that spending time with others does more than make you happy, it makes you more empathetic. In a research study done by Inbal Ben-Ami Bartal, et al., rats who were exposed to other rats were more likely to help that.
There were two types of rats used, while type albino rats, and rats with black fur. Free albino rats were trapped with other albino rats they had never spent time with before. For twelve days the free albino rats interacted with a new albino rat on each day. When these albino “strangers” were locked in a cage that the free albinos were able to open, the free albinos unlocked the cage, giving the other rat freedom. However, when presented with a black-furred rat, the free albino rats did not open the locked cages. This indicates that having exposure to a certain kind of rat, not just any rat, increases prosocial behavior towards that specific rat group.
Next, free albino rats were housed with black-furred rats for two weeks, then re-housed with albino rats for another two weeks. These free albino rats were then more likely to free a black-furred rat when given the chance. Therefore, rats do not need to become familiar with a specific rat, but rather, with a type of rat group. So, their empathy extends beyond the specific familiars they are used to to include an entire rat group.
The researchers then added a twist to the experiment: they housed newborn albino rats with a black-furred foster family. These albino rats were then only exposed to the black0furred rats, not other albino rats. Later, these albino rats unlocked cages for black-furred rats, but not albino rats.
Main author Inbal Ben-Ami Bartal said, “Rats are apparently able to categorize others into groups and modify their social behavior according to group membership.” Therefore, it’s not genetic similarity, but familiarity, that increases prosocial behavior in rats.
Another researcher in the study, Peggy Mason, added, “Exposure to and interaction with different types of individuals motivates them to act well toward others that may or may not look like them. I think these results have a lot to say about human society.”
Original paper: “Pro-social behavior in rats is modulated by social experience” (DOI: 10.7554/eLife.01385.001) can be found here.