Lil' Wayne once said, "Off the rat, he won't rat no more." Elegant as Weezy's lyrics were, he might be using "rat" a little incorrectly, since it turns out rats are predisposed toward helping each other (among other things). Rats, long known to be social creatures, will help each other escape from cages, and display actual empathy.
In a study by the University of Chicago, a rat was placed inside a clear cage, which could be opened from the outside, and another rat was placed in "freedom" outside the cage for one hour at a time.
At first, the free rat attacked the cage (seemingly to open it; not the way beta fish attack the glass in attempt to attack each other). After about a week, the free rat learned how to open the cage and did so.
Inbal Ben-Ami Bartal, coauthor of the study and psychologist for University of Chicago, said, "It's very obvious that it is intentional. They walk right up to the door and open the door."
The study was recreated with an empty cage. Of 40 rats, five learned how to open the empty cage (or cages with stuffed replicas of rats), while 23 of 30 learned how to free live rats.
This proves empathy because the "free" rat feels distress while another rat is trapped. Hence the opening of the cage. When the trapped rat is free, the original free rat no longer feels distress, no longer has reason to open the cage.
The study was then recreated by putting chocolate, which rats apparently love (who knew), in the cages. The rats freed chocolate as often as they did other rats. They even saved some for their rat buddies, which Bartal said was "shocking," but "they actually carried it out of the restrainer sometimes but did not eat it."
As exciting as this study is, it does call this into question: if you were locked in a room and your friend rescued you, would he also bring chocolate?