MP: Well, the question of multi-tasking is a complicated one, because there are many grains or levels at which we could ask the question. In fact, we are pretty limited in what we can do at any one given time. But given time is usually thought of in psychological studies as in the millisecond range. However, we can shift from task to task, and of course we all do this during the course of a day. That can be pretty efficient—and in that sense we can multi-task, start on one task, and switch to something else, and come back again.

What the psychologist is usually saying when he says there’s a limit to attention is really to look at this millisecond range—what we’re doing at any one time. So if you’re listening to me intently, you’re going to miss things in the background. And you might feel that you’re aware of everything, but, in fact, psychological studies have shown that, really, vast changes can occur in the background. And provided they don’t produce the cues—the particular physical cues that lead to reorienting of attention—you’ll just miss them. So, at one level, we’re pretty severely limited; at another level, gross level of time, we are able to shift from task to task. Of course, this is something that depends a lot on our interest and on our training and so on.

RJ: In shifting from task to task at that level, does it take a certain amount of time to really get into the task where you can pay full attention to it?

MP: Yes, and that time is definitely measurable by psychological experiment. On the other hand, it isn’t like twenty minutes or so. It’s in, probably, millisecond-to-second range to shift from one task to another. In terms of the overall day, or what people are trying to talk about in terms of being able to do more than one thing at a time, in the gross lay sense, it isn’t really severe punishment, but it does cost. And these costs can be measured.

RJ: Is there any indication that young people, for instance, who were brought up instant-messaging while watching TV, are able to do this better than adults? And that, kind of, some of the issues people are bringing up about information overload and that sort of thing actually has to do with the amount of training?

MP: Uh, the question about whether young people, being raised in a more Web culture, are better able to do this than their older contemporaries not raised in that culture… as far as I know, that question hasn’t really been definitively answered. My guess would be that they’ll have made certain adaptations, or developed certain skills. Anyway, in older age, we lose some of these abilities, probably due to changes in the nervous system that come with age, so although I can’t really say that the definitive experiments have been done, it seems quite likely that people raised with access to all the information that’s available on the Web with the click of a button are maybe better able to take advantage of it than people who are always having to write things down, go to the library sometime later and so on.

RJ: So if there’s a finite amount that we can pay attention to at a given time, is it possible to overload the brain circuitry over a larger period of time? Throughout our day, the more things we’re exposed to, the more stimulus, that the less our ability is to pay attention?

MP: The question of whether we can overload and get fatigue… again I might have a little difficulty in pointing to the best studies that deal with this, but it seems almost certain that we can get fatigued from high mental effort during the day. And that is like any other kind of fatigue; it requires a certain amount of restoration. There are psychological theories to this effect—that restoration is required after intense mental effort—and that seems likely to be the case. But, again, I’m not certain we have the definitive answer to this question.

RJ: Is that the sort of thing where, if you were exposed to lots of flashing advertisements and signs, thatpotentially those could be forces that wear us down?

Russ Juskalian is a contributor to The Observatory and a freelance writer.