Play Pharrell Williams’ “Happy” and I bet an earworm wriggles its way into your brain. It’ll start innocently enough, a few snippets of the international chart-topping and impossibly infectious track on loop. But later that day, you might find yourself humming it as you prepare dinner. Wake up the next morning and it may still be burrowed deep, the refrain sliding into your consciousness without warning.

Also known as involuntary musical imagery (INMI), the experience of spontaneously recalling a tune and then getting it stuck in your head on repeat is a common one. Its prevalence lies in the myriad ways that we can catch one. “The most frequent trigger is recent exposure to the actual song,” says Dr. Kelly Jakubowski, a postdoctoral research assistant at Durham University�...