It has been observed for many years that mice appear to show empathy for other mice in pain; scientists call this "emotional contagion." It has also been demonstrated that cage mates will offer what seems to be comfort to their apparently distressed companion, which then seems to reduce the comforting mouse's pain symptoms. This apparently altruistic behavior in mice has been refuted by those in the scientific community who say that, while it may look to us as though these are altruistic behaviors, they do not indicate that the mouse was acting out of any motivation to help another, but just as possibly working to reduce their own distressful response to hearing and seeing another's distress, an ultimately selfish motivation.
The current University of Chicago study was carefully designed to prove the behavior is, indeed, altruism. They did this by including the treats aspect of the experiment--showing that the rats would free their cage-mate from a trap even though it meant having to share their chocolate chips with them--proving that the behavior was performed without selfish intent and against their own organism's best interest (if you define "best interest" as hoarding food). Indeed, if a rescuer first ate some of the chocolate, they would save a piece for the trapped rat and then hand it to them when their companion was finally liberated. Rescue-rats took three to seven days of non-stop work and concentration to learn how to open their distressed companion's trap to free them. They did not put effort into opening an empty trap or a trap holding a toy rat.
The Simple Explanation of these findings is that rats, like all other units of consciousness, follow the Golden Rule. It is not anthropomorphic to attribute altruism to animals. Or selfishness, which is altruism's opposite pole. The Simple Explanation says, "It is the job of every UC, no matter its hierarchical level of complexity and sophistication, to reach out laterally to its neighbors, working together for the good of all."
Go rats, go!