Study: Brain has one-track mind VU pair says it shows why phones, driving don't mix
2007-02-07

Friday, 01/26/07
By RALPH LOOS, Staff Writer


Despite common belief that the human brain is built for multitasking, two Vanderbilt scientists believe that our cerebral center is nothing more than a one-trick pony.

It's a fact our brain works hard to hide.

"As complex as it is, it struggles," said Rene Marois, an associate professor of psychology at Vanderbilt University. "While we get the impression that we are able to do two things at once, such as driving and talking on a cell phone, in reality our brain shuts down one of the functions briefly as we're taking on the other task. All the information in our brain suddenly hits a bottleneck."

Marois and Paul Dux, a postdoctoral research associate in psychology, are the first to identify the regions of the brain responsible for what previous researchers labeled the "bottleneck."

Results of the Vanderbilt duo's work are timely as Tennessee and other states consider banning the use of cell phones while driving.

Tasks 'bottleneck' in brain

Making an argument for such a ban was not the goal of the research, though Marois and Dux admit their work is likely to be used as a reference down the road.

"We were interested in trying to understand limitations and in finding where in the brain this area called an information bottleneck might be taking place," Dux said. "We found that tasks as simple as pressing a button when a visual stimulus appears caused a delay in brain function."

They also suggest that other simple tasks, such as opening a door and lighting a cigarette simultaneously, come at a cost to brainpower.

The delay is known as dual-task interference, and the researchers said driving presents particular challenges.

"While we are driving, we are bombarded with visual information," Marois said. "Our research features neurological evidence that the brain cannot effectively do two things at the same time. Even those people who think using a headset with their cell phone while driving is safe, but they're still doing two cognitively demanding tasks at once."

To identify the bottleneck, they used functional magnetic resonance imaging, a technology that reveals the brain areas active in mental tasks by mapping changes in the blood's oxygen levels. Dux and Marois rapidly sampled brain activity while subjects performed two demanding tasks: pressing the appropriate computer key in response to hearing one of eight possible sounds and uttering an appropriate response to seeing images.

Brain puts driving on hold

The results revealed that the central bottleneck was caused by the inability of parts of the brain to process the two tasks at once.

Each brain region that responded to tasks and showed neural activity was slotted, or prioritized.

"The neural response to the second task was postponed until the response to the first was completed," Dux said. "So when you're driving and you decide to dial someone up on the phone, you are actually putting the driving on hold, as far as your brain is concerned. That can be dangerous."

Brain research or not, some Tennesseans think cell phones and driving should be banned. Period. The only legislation on the books in Tennessee deals with cell phones while driving through a school zone.

"Not long ago I was stopped at a red light and saw a woman drive through the intersection talking on a cell phone with one hand and smoking a cigarette with the other," said Mary Spicer of Nashville. "I guess she was driving with her knees. It's getting ridiculous, and I've written our lawmakers about putting a law on the books."

Not everyone agrees.

"Education is the answer, not legislation," Barry Breen of Nashville said. "Cell phones are another additional distraction while driving. Any number of distractions is present when driving. Should reaching to adjust the CD player also be banned ... how about turning to talk to someone in the vehicle, etc.?"

The National Highway Traffic Safety Administration has published a study indicating that driver distractions
were blamed for 20 to 30 percent of all vehicular accidents in 2004.

Marois and Dux say they do not talk on their cell phones while driving.

"Dual-tasking can cost up to a full second, and that's a good period when you're moving the speed limit," Dux said.

Research doesn't end

Next up for the researchers is the exploration of what is happening in the bottleneck to slow performance.

"We may look at people involved doing complex activities like flying a plane to see how their brains react to multitasking," Dux said. "A pilot seems to be doing many things at once. But is his brain doing more than one thing at a time?"

There's at least one aspect of such a study that the Vanderbilt duo won't have to worry about.Passengers aren't the only ones on an airline not allowed to use their cell phones in-flight.


Source: Tennessean.com