Our minds may wander during boring tasks because daydreaming is actually the brain's normal state, rather than a pointless distraction, according to a new U.S. study.

The researchers, reporting their findings today in the U.S. journal, Science, found that daydreaming could be the result of the brain mulling over important - but not immediately relevant - issues when the external environment ceases to pose interesting and engaging problems.

According to Mason, the most important question is why our brains evolved to wander at all. His team suggests that perhaps it keeps our brains aroused during mundane tasks, or simply that our brains may wander because they can.

"In a sense these thoughts reflect an amazing capacity on our part to multi-task," said Mason. "It is as if we have a sense of how much [attention] we have 'left over' and allocate these resources to working out some problem or anticipating what we have to do in the near future."