Got a tough problem to solve? Try daydreaming.

Contrary to the notion that daydreaming is a sign of laziness, letting the mind wander can actually let the parts of the brain associated with problem-solving become active, a new study finds.

Kalina Christoff of the University of British Columbia in Canada and her colleagues placed study participants inside an fMRI scanner, where they performed the simple routine task of pushing a button when numbers appear on a screen. The researchers tracked subjects' attentiveness moment-to-moment through brain scans, subjective reports from subjects and by tracking their performance on the task.

Until now, scientists had thought that the brain's "default network," which is linked to easy, routine mental activity, was the only part of the brain that remains active when the mind wanders. But in the study subjects, the brain's "executive network" — associated with high-level, complex problem-solving — also lit up.

The less subjects were aware that their mind was wandering, the more both networks were activated.

"This study shows our brains are very active when we daydream – much more active than when we focus on routine tasks," Christoff said.

The findings, detailed in the May 11 issue of the journal Proceedings of the National Academy of Sciences, suggest that daydreaming is an important cognitive state where we may unconsciously turn our attention from immediate tasks to sort through important problems in our lives.

"When you daydream, you may not be achieving your immediate goal – say reading a book or paying attention in class – but your mind may be taking that time to address more important questions in your life, such as advancing your career or personal relationships," Christoff said.

That's particularly good news, because daydreaming can occupy as much as one third of our waking lives, previous studies have found.