Monday, March 26, 2007

The bottleneck in the brain

The New York Times brings us more evidence that multitasking doesn't work well:

"Multitasking is going to slow you down, increasing the chances of mistakes," said David E. Meyer, a cognitive scientist and director of the Brain, Cognition and Action Laboratory at the University of Michigan. "Disruptions and interruptions are a bad deal from the standpoint of our ability to process information."

The human brain, with its hundred billion neurons and hundreds of trillions of synaptic connections, is a cognitive powerhouse in many ways. "But a core limitation is an inability to concentrate on two things at once," said René Marois, a neuroscientist and director of the Human Information Processing Laboratory at Vanderbilt University.

Mr. Marois and three other Vanderbilt researchers reported in an article last December in the journal Neuron that they used magnetic resonance imaging to pinpoint the bottleneck in the brain and to measure how much efficiency is lost when trying to handle two tasks at once.

Study participants were given two tasks and were asked to respond to sounds and images. The first was to press the correct key on a computer keyboard after hearing one of eight sounds. The other task was to speak the correct vowel after seeing one of eight images.

The researchers said that they did not see a delay if the participants were given the tasks one at a time. But the researchers found that response to the second task was delayed by up to a second when the study participants were given the two tasks at about the same time.

In many daily tasks, of course, a lost second is unimportant. But one implication of the Vanderbilt research, Mr. Marois said, is that talking on a cellphone while driving a car is dangerous. A one-second delay in response time at 60 miles an hour could be fatal, he noted.

"We are under the impression that we have this brain that can do more than it often can," observed Mr. Marois, who said he turns off his cellphone when driving.
A slideshow accompanies the article, with images of New Yorkers talking and texting while biking, skateboarding, and walking.
Slow Down, Multitaskers; Don’t Read in Traffic (New York Times)

Related posts
Multitaskers, take note
Multitasking makes you stupid
On the advantages of writing by hand
On continuous partial attention
On continuous partial attention and reading habits
On wireless connections in classrooms

comments: 3

Eustace Bright said...

Humans' desire to multitask is as interesting as our inability to do it. Perhaps we overload our senses because of a misfiring of our productivity gene (gross simplification, I bet), or because we modern individuals have grown uncomfortable with stillness between activities, a silence that endangers us to the sensation of spiritual emptiness and an ironic disconnect from nature and other people.

A different explanation would be that whereas the study asked subjects to do two activities requiring active (conscious) thinking (the keypad layout and its association with the sounds/symbols was almost certainly novel), sometimes people aren't multitasking two activities that both require conscious attention. Driving, playing a drum set, and typing are examples of activities that demonstrate the ability of the brain to perform activities subconsciously for sustained periods. (Have you ever noticed, likely with panic, that you have not been paying attention to your driving for more than one turn or stop and go?) Thus, I would be interested to see the results of a similar study wherein at least one of the activities is a very familiar activity, trained into the motor cortex. I wonder if the results would be similar or different!

Michael Leddy said...

The driving scenario is a puzzling one -- is it that we're not paying attention, or that we're not aware that we're paying attention?

My son did some research on multitasking recently and found one explanation of its appeal in brain chemistry -- when the brain has data rapidly surging through it, it produces more dopamine, which makes us happier, at least for the moment.

I share your sense that for many people multitasking distracts them from difficult realities -- always texting, always with earbuds, always not quite otherwise alone.

Eustace Bright said...

What a great study your son has done! The result you mention matches with my own emotional experience.

Regarding driving, the degree and frequency of "novelty" is probably the deciding factor on how far into the subconscious an activity is monitored by the brain. Walking takes little active thought, and even hard thinking can be done while walking. The introduction of lightposts or other pedestrians in the path may cause disruption to the extent that the thinker is not already familiar enough with that configuration of obstacles. If the configuration is new, then the user has a novel situation that requires figuring out. Even a second or third (or more) time the obstruction pattern is encountered, I hypothesize that the thinker will have to set aside his thoughts to remember how to navigate. Brain scans would determine rather easily whether any tasks that once were the realm of conscious execution can be habituated to the point that they can be accomplished in the unconcious parts of the brain simultaneously with a different task in the conscious, or if, by contrast, it is not possible for the brain to do this, and it has to simply flit back and forth quickly (so quickly that we don't realize we're thinking about it, as you seem to have put it). My guess is that we'll find true (that is, simutaneous) multitasking theoretically possible, and indeed evident in some of our behaviors, but prohibitively difficult to attain for complex behaviors that constantly indroduce "novel" problems, such as talking on a phone (who knows what the person is going to say!) or listening to a song or all driving conditions.