In a series of papers published in 2012, a British musical psychologist named Victoria Williamson led a research group that spent time studying earworms. They asked people to describe the songs stuck in their heads, and found that very few songs occurred more than once. People did tend to report songs like Jingle Bells around the holidays, and pop songs that were constantly on the radio showed up a lot more in the answers too. In another part of the study Williamson and her team with the BBC, surveying radio listeners to try and figure out what gave them earworms. Unsurpisingly, the most common cause was recent or repeated exposre to a song. So the top 40, and Jingle
