What does your brain look like on Christmas? That's what Danish researchers set out to find out, using fMRI brain scans to determine who has "bah humbug" syndrome and who truly believes.
When the researchers showed pictures to two groups of people, the fMRI showed different areas of the brain associated with spirituality, self transcendence and recognition of facial emotion lighting up in response in the people who had positive associations with Christmas traditions, compared to a calmer response in a group that didn't celebrate Christmas.
The study, which was published in the BMJ Christmas issue, known for its spoofs and quirky research, spotlights how fMRI research often overreaches, producing questionable results.
So did the research actually pinpoint the Christmas spirit?
"If you dig deep enough, you'll find all the explanations you're looking for," study co-author Bryan Haddock of Rigshospitalet, a hospital affiliated with Copenhagen University in Denmark, said.
"They didn't control for Hanukkah," Michael Atherton, a former educational neuroscience researcher at the University of Minnesota, quipped.
"If they'd looked at Hanukkah memories I'd be surprised if they didn't get the same areas [to show activation]," he said. "It could be for birthdays, too - anything involving eating and opening presents."
You can't know, in other words, that 20 or 30 other types of experiences wouldn't trigger the same thing.
The Christmas spirit researchers, who met at nights and on weekends to work on the project, would agree. It's too difficult, they admit, to do a proper study on exactly what goes on in the brain when people think about a holiday.
"It's a bit of a debate we're trying to make lighter," Haddock said. "You can argue that you can understand the Christmas spirit better from this, or a Grinch can say, this is bollocks - localizing it doesn't make anyone any wiser."
The BMJ Christmas issue often highlights big issues in medical research with seemingly trivial subject matter. In this case, the researchers took a break from their regular research on migraines to do the Christmas brain scans.
"Although merry and intriguing, these findings should be interpreted with caution," they explain in the press release. "Something as magical and complex as the Christmas spirit cannot be fully explained by, or limited to, the mapped brain activity alone."