Oh Mickey, you’re so fine, you’re so fine you blow my mind. Hey Mickey.

Chances are you’ve heard that song before — Mickey, by Toni Basil. And there’s also a pretty good chance that sometime today, that song will pop up in your head when you least expect it. That’s just the way it is with catchy tunes; they get stuck in our heads. Commonly called “earworms,” scientists still aren’t exactly sure why our brains hold onto these songs, but a new study suggests it could relate to the size and shape of a person’s brain.

Published in the journal Consciousness and Cognition , the study found that the frequency in which people heard earworms, which are commonly called involuntary musical imagery in the medical community, was associated with varying thicknesses in different parts of the brain. Specifically, those who experienced them the most had thicker Heschl’s gyri and right inferior frontal gyri. The former is an area involved in auditory perception and musical memory, while the latter plays a role in pitch memory, CBS News reported.

They also found that participants’ brain structures were different depending on whether they perceived the music as annoying or helpful toward going about their daily routines. Among those who found it helpful, the right parahippocampal area of the brain larger — this part of the brain is involved in memory encoding and retreival. The researchers also found these people were better able to suppress the earworms. On the other hand, those who found the earworms annoying tended to have more grey matter in the temporal lobe, where emotions are regulated.

“Areas in the auditory cortex that we know are active when you actually listen to music seem to be physically different in people who are experiencing music that’s not even there,” study co-author Lauren Stewart, of Goldsmith’s, University of London, told New Scientist.

The study was small, only involving 44 participants. Each of them filled out two surveys: the Involuntary Musical Imagery Scale and the Goldsmith’s Musical Sophistication Index. The first asked them how often they experienced the earworms, how much they moved to them, and how helpful they were throughout the day. The second survey asked about the participants’ music listening habits — how much they listened to music or wrote it and how often they attended concerts, for example. They then underwent magnetic resonance imaging (MRI) scans so researchers could see how their answers correlated with their brains’ structures.

The researchers stressed their study didn’t prove having certain brain shapes caused earworms or their subsequent emotions. Of course, these emotions could arise from a combination of factors, such as the situation a person is in when they experience an earworm — if they’re in a bad mood, chances are they won’t perceive the earworm positively, and vice versa.

Other studies have also shown a link between a higher frequency of earworms and neuroticism and non-clinical levels of obsessive compulsion. “These people tend to have more repeated thought processes in general, so it’s perhaps not a surprise that these are reflected in their experiences of mental music as well,” Victoria Williamson, a researcher who has studied the types of music that become catchy, told Science Friday. Perhaps these people’s brain structures affect how they perceive earworms. Further research will determine these answers as well as what exactly causes earworms in the first place. As for how to stop them, just chew some gum .

Source: Farrugia N, Jakubowski K, Cusack R, Stewart L. Tunes stuck in your brain: The frequency and affective evaluation of involuntary musical imagery correlate with cortical structure. Consciousness and Cognition . 2015.