You might have thought all the hours whiled away gazing wistfully out of the window in the summertime would dent your performance at work - but it turns out we're actually sharper during the summer.
A new study by a team at the University of Liege has found people's brains are sharper and attention spans higher around the summer solstice, while they're at their slowest in the depths of winter.
The team deprived 28 people of sleep for two days, then kept them in a low-lit environment for another three days. After that, they were asked to perform tasks on a computer while their brains were monitored.
The study, published in Proceedings of the National Academy of Sciences, suggested the body can keep track of the seasons, even if it's not exposed to any light.
"The study provides compelling evidence for previously unappreciated annual variations in the cerebral activity required to sustain ongoing cognitive processes," said the authors.
"For [a] sustained attention task, the maximum and minimum responses were located around summer and winter solstices, respectively."