During the holidays, if kids become brats, you can shout with a straight face, “Start acting like rats!’’ According to a study in the journal Science, University of Chicago researchers discovered that lab rats can show empathy — a quality not previously demonstrated in rodents — at levels that are rare even in primates. Free rats sensed distress in caged rats and worked tirelessly to free them. When chocolate chips were added to the experiment, the free rat did not selfishly gobble them up and let the caged rat languish. It still freed the other rat and shared the sweets. Researchers hope their observations will inform studies of human empathy. Despite the rat’s image as the first creature to abandon a sinking ship, the new finding may inspire a rising tide of concern for one’s fellow beings, especially during the holidays. If even rats put others first, surely humans can, too.