We're all familiar with songs getting stuck in our head while we're awake, but it turns out this can happen during sleep as well. A new study investigating the phenomenon indicates that earworms invading our brains at night could cause problems in getting to sleep and staying asleep.
"Our brains continue to process music even when none is playing, including apparently while we are asleep," says neuroscientist Michael Scullin from Baylor University.
He and colleagues used surveys of 199 people, as well as a sleep lab test involving 50 volunteers, to measure how listening to music before bedtime affects sleep. In particular, the team focused on catchy earworms, technically known as 'involuntary musical imagery'.
In the survey part of the study, participants who frequently listened to music during the day were more likely to report persistent nighttime earworms, which then had a negative effect on sleep quality through the night.
For the lab test, individuals were played instrumental or standard versions of Shake It Off by Taylor Swift, Call Me Maybe by Carly Rae Jepsen, and Don't Stop Believin' by Journey. Polysomnography tests were used to measure subsequent sleep quality.
Earworms were reported throughout the night by participants, with those catching an earworm taking longer to fall asleep, spending more time in the light stages of sleep, and waking up more times during the night.
Surprisingly, the instrumental versions of the songs caused about twice as many earworms (and more subsequent sleep problems) than the versions with vocals.
"We thought that people would have earworms at bedtime when they were trying to fall asleep, but we certainly didn't know that people would report regularly waking up from sleep with an earworm," says Scullin. "But we saw that in both the survey and experimental study."
Brain scans showed more slow oscillations during sleep in the people who reported getting an earworm – a sign of memory reactivation. The brain region involved, the primary audio cortex, is also linked to earworm processing when people are awake.
Past studies have linked late-night music listening with better sleep in those with insomnia, perhaps because it can relax the body. The researchers behind the new study suggest that actually it might be worse for our sleep – that even after the tunes stop, our brains continue to process them for several hours.
Scullin suggests avoiding listening to music right before bed to limit the chance of a catchy tune taking hold in our minds. Engaging in some other cognitive activity before sleeping, like making a list of jobs for the next day, might also help clear the mind, Scullin says.
"Everyone knows that music listening feels good," says Scullin. "Adolescents and young adults routinely listen to music near bedtime. But sometimes you can have too much of a good thing."
"The more you listen to music, the more likely you are to catch an earworm that won't go away at bedtime. When that happens, chances are your sleep is going to suffer."
The research has been published in Psychological Science.