You've probably heard that multitasking will rot your brain. I've written plenty of posts on the subject myself. Here's one saying that doing two or more things at once makes you as dumb as being stoned. Here's another on research showing that multitasking physically shrinks your brain (yes, really).

But science isn't static. One year's ironclad truth, is the next's discarded theory. Even the most accepted ideas can be overturned by fresh evidence. Is this about to happen to the case against multitasking?

Does exercising willpower just generate more of it?

That's the focus on a fascinating INSEAD Knowledge post with the heretical title "In Defense of Multitasking." In it, INSEAD professor Steven Sweldens points out that some of psychology's most celebrated notions -- such as the idea of willpower as a finite resource -- have recently come under assault when other researchers failed to replicate headline-grabbing results. This turmoil in the discipline is apparently complicating our understanding of multitasking.

If willpower is a finite resource then multitasking is obviously a great way to fritter it away. But new experiments by Sweldens' and colleagues are calling this understanding into question. Perhaps, instead, willpower is more like a beefy friend you can call up to help you with difficult tasks. If you manage to enlist this brawny buddy to help you with one task, it just makes sense have it pitch in with others while it's around. If that model holds, then multitasking is a smart way to accomplish more.

The researchers tested out this alternate understanding of willpower and multitasking by asking study subjects to do two tasks that draw on self-control simultaneously -- ignoring subtitles on a muted video and resisting gobbling a bowl of Pringles, for example.

In contrast to what you'd expect if willpower is indeed a limited resource, subjects' whose willpower was asked to do double duty actually did better at controlling themselves than those facing only a single task. Activating willpower for one task seemed to make completing a second easier.

The running start approach to tackling your hardest tasks

How can you put that insight to use in real life? The findings suggest that if you are already "in the zone" doing for one task and have some energy to spare, switching straight to another might give you a lift, much like a running start can help an athlete clear a higher hurdle than they could surmount from a standstill.

Multitasking, in this sense of using your momentum to leapfrog from one task to another, may actually be useful.

Or, if you don't have multiple tasks to pair together, Sweldens suggests another way to put his study to use: "Next time you need a boost in concentration, try listening to music at a very low volume as you work. The activity of mentally cancelling out the sound should be enough to tap the brain's enormous reserves of willpower and focus."

No, this isn't permission to check your email 57 times a day.

A word of caution: while trying to immediately leapfrog from one task to another might be a good idea, capitalizing on the willpower you've already summoned, the researchers found no such benefit to doing two hard things sequentially. That means if you tackle one difficult to-do list item and then take a break to eat a sandwich or check your email, you'll probably find getting started on the next pretty arduous.

That means that while the current blanket ban on multitasking might need some amending, these findings shouldn't be seen as an endorsement for constant inbox checks or near constant glances at your phone. That sort of multitasking is pretty much guaranteed to result in nothing good.

"A certain amount of tunnel vision is necessary to get things done nowadays, with incessantly pinging phones and scrolling social-media timelines providing powerful distractions," concedes Sweldens.