Because you’re unfamiliar with the lyrics. People can recall the first verse of a song, but after the chorus, they might stumble over the words. The song becomes incomplete, which transforms into an intrusive thought, according to Ira Hyman Jr. of Western Washington University. Songs intrude during tasks that are either difficult, causing the mind to wander, or easy, allowing repetitive thoughts to enter. To flush out these stuck songs, called earworms, find an engaging task that requires the auditory and verbal components of your working memory, like reading a good book or watching a favorite show.—Anahad O’Connor, from The New York Times