Hey Jude: Get that song out my head!

In most cases, earworms will disappear after a few minutes. In some cases, earworms can last hours or even days. McNally-Gagnon is also a musician, who is often infected, which is why she wanted to better understand how and why it occurs.

For starters, she asked French-speaking Internet users to rank 100 pop songs according to their ability to be compulsively repeated within one's mind. The top five were: Singing in the Rain (Gene Kelly), Live Is Life (Opus), Don't Worry, Be Happy (Bobby McFerrin), I Will Survive (Gloria Gaynor) and, in first place, Ça fait rire les oiseaux by Caribbean sensation La Compagnie Créole. (A complete list is published at www.brams.org).

In the laboratory, McNally-Gagnon and her thesis director Sylvie Hébert, professor at the University of Montreal School of Speech Therapy and Audiology and a member of the International Laboratory for Brain, Music and Sound Research (BRAMS), asked 18 musicians and 18 non-musicians to hum and record their obsessive songs and note their emotional state before and after. The researchers found earworm infections last longer with musicians than with non-musicians.

The phenomenon occurs when subjects are usually in a positive emotional state and keeping busy with non-intellectual activities such as walking, which requires little concentration. "Perhaps the phenomenon occurs to prevent brooding or to change moods," says Hébert.

The study also revealed that auditive memory in people is can accurately replicate songs. Humming among musicians was only one key off original recordings, while non-musicians were off by two keys.

McNally-Gagnon and Hébert now plan to study earworms using MRI or Transcranial Magnetic Stimulation technology. "The only such studies that have been conducted were on test subjects who mentally imagined a song," says Hébert. "We believe the neurological process is different with earworms, because the phenomenon is involuntary."