The old adage “When you want a job done right, give it to a busy man” might have a basis in science. Researchers at the University of Texas, Dallas, have just released a study which purports that people with the busiest schedules perform best on cognitive tests. The work was published in Frontiers in Aging Neuroscience.

What is most interesting is that researchers arrived at their conclusions coming from the completely opposite direction. Their hypothesis was that harried, mentally taxed, so-called “stressed out” people would be “wearing out their brains,” and end up with worse cognition.

"On every test, those who had fuller days and less time on their hands outperformed those who were less busy. We were somewhat surprised, I have to be honest," Professor Denise Park, one of the study's authors, told NPR.

The researchers now theorize that the daily mental grind of completing task after task is building our brains up and improving mental skills. That performance gap between the busy and the free seemed to be wider among older participants too, "which is particularly exciting," Park says.

It's exciting because the results imply that staying active in old age could protect against dementia. Previous findings have corroborated this, and that includes not just mental effort but physical exertion.

The researchers have stopped short of drawing too tight a corollary between busy-ness and being sharp. "It could be that people become slowly less busy over their lifetime as dementia [sets in]," Park says. That would make less busyness a consequence of failing cognition, not the other way around.

So what's the take-away here? Should we all start burning the candle at both ends in the hope of finishing those Sudoku puzzles more quickly? Park cautions against placing too much value on being chronically busy before its effect on more than our cognition was measured.  "Maybe those people are experiencing some negative effects from a lifetime of busyness. We haven't looked at that," she says.