Earworms: What are they and how do they get in our heads?

We've all gotten them before: songs that have become so engrained in our memory that they are almost impossible to get out. I am talking about earworms. The term "earworm" was coined by psychologist James Kellaris and he likes to describe it as a "cognitive itch created by a catchy tune". There is no temporary solution for getting rid of an earworm other than repeating it over and over in your mind, until it is eventually replaced with other thoughts.
Most earworms come from songs that have a repetitive pattern or an unusual time signature. Due to these qualities, the songs become intriguing or easily reproduced. Many psychologists have theorized that earworms could be the brain's way of trying to close a gap in rhythm, scale, or lyrics. Although there is no clear explanation as to why earworms occur, these previous examples could help explain something.
Research by Kellaris shows that 98% of individuals experience earworms. Men and women experience earworms, but studies have shown that these earworms last longer for women and irritate them far more than men. Some alternative names for earworms are: "humsickness", "repetunitis", "obsessive musical thought", and "tune wedgy".
There is no guaranteed way to destroy an earworm but there are ways to offset that annoying tune in your head: turn on the radio, play a different melody on a nearby instrument, and even chew on a cinnamon stick (as done by one of Kellaris's subjects). Earworms can keep one interested for some time, but in the long run they can be very annoying. All I can say is keep listening to that tune in your head, it may go away sooner or later, or it may not.