This 2010 Frontline interview with Clifford Nass is a great explanation of the state of the art on research in multitasking. The bottom line is, we’re terrible at it, we’re not really designed to do it, and people who think they can successfully multitask really can’t.

So what gets lost?

Some things that we know get lost are, first of all, anytime you switch from one task to another, there’s something called the “task switch cost,” which basically, imagine, is I’ve got to turn off this part of the brain and turn on this part of the brain. And it’s not free; it takes time. So one thing that you lose is time.

A second thing you lose is when you’re looking at unrelated things, our brains are built to relate things, so we have to work very, very hard when we go from one thing to another, going: “No, not the same! Not the same! Stop it! Stop it!”….

At the end of the day, it seems like it’s affecting things like ability to remember long term, ability to handle analytic reasoning, ability to switch properly, etc., if this stuff is, again, … trained rather than inborn. If it’s inborn, what we’re losing is the ability to do a lot of things that we’re doing. We’re doing things much, much poorer and less efficiently in time. So it’s actually costing us time….

You’re confident of that?

The demonstration that when you ask people to do two things at once they’re less efficient has been demonstrated over and over and over. No one talks about it — I don’t know why — but in fact there’s no contradictory evidence to this for about the last 15, 20 years. Everything [as] simple as the little feed at the bottom of a news show, the little text, studies have shown that that distracts people. They remember both less. Studies on asking people to read something and at the same time listen to something show those effects. So there’s really, in some sense, no surprise there. There’s denial, but there’s no surprise.

The surprise here is that what happens when you chronically multitask, you’re multitasking all the time, and then you don’t multitask, what we’re finding is people are not turning off the multitasking switch in their [brain] — we think there’s a switch in the brain; we don’t know for sure — that says: “Stop using the things I do with multitasking. Focus. Be organized. Don’t switch. Don’t waste energy switching.” And that doesn’t seem to be turned off in people who multitask all the time.

I think in a sense my contemplative computing work is about how you switch the multitasking part of your brain off, and start concentrating again.