Is multitasking a myth?

00:00PROFESSOR: How do you feel about people driving while talking on their cell phones? Smart, not smart? Also consider the case like let's suppose that you have a hands-free setup. So you don't have to be looking down on your cell phone or typing away or holding your cell phone.

00:17Maybe that's OK. What do you think? Is there no problem with driving while talking on your cell phone, provided you're not looking down and pecking away at it? My rule is if I am talking on my cell phone, certainly if I'm turning left, I put the damn cell phone on my lap.

00:33And I tell whoever it is, I can't talk to you and turn left at the same time. Anyway, the real question here is not for me to lecture you about driving, but to think about why is that a problem? Why can't you talk to a person and pay attention to driving?

00:51What is the big deal? And so the intuition is we have some kind of limited processing ability. OK? We're not super, super computers who can just do millions of things at once. We have some kind of limit in how much stuff we can handle. And I think everybody will have this intuition.

01:09You can't think about lots of different things at once. I like to think of this as the toaster model of cognition. That is you plug in the toaster. And the lights dim. So if everything's on the same circuit, there's some kind of unitary thing resource that's limited, and more of it goes here, less of it goes here.

01:28So obviously, we don't have simple circuits like that in our brain. And the relevant scarce commodity isn't just electricity. It's not electrons. It's some other kind of occult thing we don't totally understand. But there's still some sense in which some of our mental processes are on the same circuit.

01:46So think about this. How many people feel like you can listen to music and read difficult stuff at the same time? Raise your-- I'm curious. How many people feel like they can do that? Only a few. Yeah, I can't do it at all, like at all. Like, even background music that I don't even care that much about-- no.

02:03Someday, I mean, I think these are really stunning individual differences. I don't know if there's any good work on it. I haven't seen it. But I think it's really interesting. How about recognizing faces and scenes at the same time? Can you do that?

02:14Yeah? How many people feel like you can recognize a face and a scene at the same time? In fact, Michael Cohen, who gave that lecture on brain-computer interfaces a month ago or so, showed some beautiful work that actually you are better at recognizing a face and a scene presented simultaneously than two faces or two scenes.

02:36Can you think why that might be? So what Michael showed is not just that you can recognize a face and hold it in working memory, a face and a scene, better than two faces or two scenes, but the degree to which you have that cost of doing two things in one category, rather than spreading over two categories, is linearly proportional to how different the activation patterns are for those categories in the ventral visual pathway.

03:01So faces and scenes are totally different from each other. And so you get a big benefit for separating your two items across faces and scenes. Other things that are more similar in their pattern of response in the ventral pathway, like faces and bodies, you get a smaller benefit.

03:16So it's consistent with this idea that to the degree that we have separate processors, you can do, to some extent, processing in parallel.