Friday, June 25, 2010

Multi-tasking and Memory, One More Time

I have talked about the problems of multi-tasking before. But this trend among youg people is so pernicious and damaging, I just have to bring it up again.

A whole new generation of multi-taskers is upon us. These young people know how to use cell phones, text messages, the Web, video games, IPods, and assorted other electronic gizmos, often at the same time. Sometimes, driving a car is thrown in for good measure (until an accident occurs).

I work with secondary school teachers, and most of them are in awe of these kids. I have seen teachers brag about how talented their own kids must be because they are such impressive multi-taskers. Increasingly, however, teachers come to realize that multi-tasking intereferes with learning. Some teachers are particularly upset with cell phones, which they try to ban, with little success. Talk about trying to take candy from a baby! In the old days, we kids tried to hide reading of comic books during class. Today, the game is to hide text messaging on cell phones. Ah, such is progress.

Multi-tasking is certainly a talent, but one that exacts a high price on learning. Formal brain research has shown that the brain can only do one thing at a time. Multi-tasking is accomplished much in the manner of "multiplexing," an engineering term denoting doing one thing for an instant, then another, and another, and finally returning to the next step of the first task. All this switching is distracting and interferes with memory formation and what memory reseasrchers call "consolidation" into lasting memory.

Memory consolidation is often prevented when one event follows too soon after an initial learning event. There is a whole theory about this, called the Interference Theory of Learning. Memory of initial learning events can be blocked if you try to learn two things at once. In fact, learning may be disrupted for both things.

In a recent test of this phenomenon, a group of 29 people (17 to 30 years of age) was trained to discriminate two sound pips that differed in length by a fraction of a second. In one group of subjects, the training occurred consecutively, which ordinarily produces some inefficiency with learning because the second task interferes with remembering the first. Moreover, results from another group of subjects revealed that when practice on the two tasks was interleaved in multi-task fashion, there was no learning on either condition.

Another recent study should get your attention: a group of study participants, divided into those that were heavy multi-taskers and those that multi-tasked only infrequently. All participants were probably at the higher end of general mental capabilities, given that they were Stanford college students. Each participant was tested in a series of thinking tests to check for any difference in the way the two types of people processed information and disciplined their attentiveness. Heavy multi-taskers were less able to sustain focus in the presence of distractions. The heavy multi-taskers performed worse even though their experience and presumed skill at multi-tasking should have made them more effective at these tasks. The heavy multi-taskers believed they were good at multi-tasking, when in fact they were bad at it.

Nor is intelligent thought likely to benefit from multi-tasking. Multi-tasking bombards working memory with scrambled and unfocused information and probably keeps the brain from learning how to optimize focus and orderly sequence thoughts. Several studies show that intelligence correlates with working memory capacity, which under the best of circumstances is limited. Working memory is the platform on which you think.Over-loading this small-capacity thinking platform just makes it harder to think straight.

So, now tell me again why multi-tasking is a good ability. While you are at it, try to convince me that it has no deleterious effect on ability to focus, sustain attention, and think.


Banai, K. et al. 2010. Learning two things at once: differential constraints on the acquisition and consolidation of perceptual learning. Neuroscience. 165: 436-444.

Ophir, E., Nass, C. and Wagner, A. D. 2009. Cognitive control in media multitaskers. Proceedings of the National Academy of Science. Aug. 24. doi: 10.1073/pnas0903620106