The neuroscientists, led by Christelle Meyer at the University of Liège in Belgium, recruited 28 young men and women at different times of year to answer questions about their mood, emotions, and alertness; have their melatonin (a hormone that regulates the sleep cycle) levels measured; and complete two psychology tasks in a brain scanner. One task was a test of vigilance and involved pressing a button as fast as possible whenever a stopwatch appeared at random intervals on-screen, and the other was a test of working memory, which involved listening to streams of letters and spotting when the current letter was the same as the one presented three items earlier. The basic idea was to see if the participants’ brain activity during these tasks was different depending on the season.

The participants’ feelings of alertness, their emotional state, and melatonin levels mostly didn’t vary with the seasons, and they actually performed equally well on both tasks in the scanner regardless of the time of year, thus undermining the idea that the winter has an adverse effect on our mental abilities (more on this shortly). One question on mood did show some seasonal variation, but participants’ moods were lowest in the fall, not winter. In terms of underlying brain function, participants’ neural activity was highest during the memory task for those participants tested in spring and lowest for those tested in the fall, so, far from being a special case, winter brain activity sat in the middle.