A catchy song or melody that gets stuck in your head and keeps playing repeatedly; also called an involuntary musical imagery.
Modern coinage combining 'ear' and 'worm' (something that burrows/persists), parallel to the German 'Ohrwurm' and related to the false belief that things could burrow into ears. Became widely used in English in the 21st century.
Scientists found that earworms are more likely to stick when you're tired, stressed, or have heard the song many times—your brain gets 'stuck' in a musical loop that actually engages multiple brain regions, which is why thinking about something else almost never works!
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