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CMU research has implications for talking on phone while driving

For brain, 2 tasks not better than 1

Friday, July 27, 2001

By Deborah Mendenhall, Post-Gazette Staff Writer

This will come as no surprise to anyone who has been cut off in traffic by an erratic driver with a cell phone attached to his ear:

Research by Carnegie Mellon University scientists shows that people can't effectively operate an automobile and talk on a cell phone -- or even to a passenger -- at the same time.

And the state of New York's legislative solution to require "hands free" cellular phones won't work either because the conversation itself, not just holding the phone, is what distracts the brain, said Marcel Just, psychology professor and leader of the CMU team.

"Viewing the brain as a work engine, talking on cell phones and having conversations while driving has to take a toll," he said. "The brain can only do so much."

Last month New York legislators responded to a growing national concern and became the first state to ban drivers from talking on hand-held cellular telephones, effective Dec. 1.

The safety issue gained momentum in April when model Niki Taylor suffered near-fatal liver damage in a car accident after a driver looked down to answer his cell phone, ran off the road and hit a utility pole.

Participants were not driving when studied, but performed tasks similar to those they would experience behind the wheel.

The study, to be published next week in the journal NeuroImage, used a noninvasive technique called functional magnetic resonance imaging, or functional MRI, to monitor the brain activity of 18 people who were performing a visual processing task while scientists read to them.

While it would seem logical that listening and looking would not compete for the brain's energy because those tasks are processed in different areas, that's not what researchers found.

"We gave the body and the brain every opportunity to do things simultaneously without competition from overlapping parts," Just said. "It turns out in some ways they are drawing on the same resource pool, and it's limited."

They found that the amount of brain activity allotted to the visual task decreased by 29 percent while the subjects also listened to a sentence.

And the subjects had even more difficulty understanding what was being said. Brain activation associated with language comprehension decreased by 53 percent if the subjects were performing a demanding visual task while trying to listen.

The same principle applies to a driver having a conversation with passengers, he said. Other research has shown that language processing is automatic, and that a person can't will himself not to process what someone else is saying. In previous tests, subjects were asked not to pay attention to what was being said. They were able to decrease brain activation, but not block it out completely by will.

Most of us instinctively turn down the radio or ask passengers to be quiet as we navigate a difficult stretch in the road.

"It is unsafe to have an engrossing conversation in demanding driving conditions, but that is not something you can legislate," Just said. "This can be handled better through driver education and promoting good practices."

No one has addressed what happens when the driver is listening to instrumental music, he said. But performing other activities while driving, such as turning around to discipline children in the back seat, putting on cosmetics or reading a book, is certainly hazardous.

"In a way, that's even worse because the driver has to take his eyes off the road," he said, "but I think people already know that and they don't need me to do a brain imaging study to tell them that looking away from the road is bad."

The research is part of a project to develop imaging methods to measure brain workload in information-driven technology environments.

It's not often discussed in brain imaging research, Just said, but the brain is a biological organ that is constrained by available energy and can only do so much work at one time.

"It's really surprising how much the brain activation goes down when trying to do two things simultaneously," he said. "It's a sizable effect."

In the study, scientists used the most recent functional MRI methods to measure activity in tiny portions of the brain, measuring a twentieth of a cubic centimeter, keeping track of how language-related activity affected the visual processing activity. The functional MRI technique records changes in blood flow, an indication of brain activation, in each portion.

The measurements were taken every three seconds while subjects listened to sentences and compared the structures of two complex three-dimensional objects.

The study showed mutual interference between separate areas of the brain that are doing very different types of thinking.

The study was funded by the Air Force Office of Scientific Research. Other members of the research team included Carnegie Mellon psychology professor Patricia Carpenter, Timothy Keller, Lisa Emery, Holly Zajac and Keith Thulborn, professor at the University of Chicago Medical Center.

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