Twenty years ago a team of psychologists revolutionized the way that we see ourselves. It all began with an experiment to see if mammals, like rats, had the capacity to laugh. When the small rodents play, they emit ultrasonic chirps, so researchers tickled them and set up recorders to amplify sounds that human ears aren’t equipped to hear. According to Peter McGraw and Joel Warner in their book The Humor Code: A Global Search for What Makes Things Funny, “when the researchers began poking at the bellies of the rats in their lab, their ultrasonic recording devices picked up the same 50-kilohertz sounds. The rats eagerly nestled their fingers for more.”

But Jeffrey Burgdorf, one of the researchers, wasn’t ready to celebrate yet — “I don’t necessarily call it laughter; I call it a signal of positive affect.” Yet, this points to a significant conclusion: Laughing is innate and we’re not alone when we do it. Sometimes we laugh when we’re nervous, or to signal our good intentions toward another person. In any case, you’ve probably laughed more today than you think you have, and that’s never a bad thing — or is it?

Don’t miss the first, second, and third entries of our Why We Laugh series, and don’t miss all of Fandor’s latest editorials, like Phantom Body Horror in Cinema and Tune in to the Radiohead Effect. Plus, check out our takes on movies like “A Star is Born” and “Roma.”