Are You Listening?

Cell Phones Impair Driving

Carnegie Mellon scientists have shown that just listening to a cell phone while driving is a significant distraction. It causes drivers to commit some of the same types of errors that can occur under the influence of alcohol. New findings by Carnegie Mellon researchers show making cell phones hands-free or voice-activated is not sufficient in eliminating these distractions.

"Drivers need to keep not only their hands on the wheel, they also have to keep their brains on the road," said Carnegie Mellon Professor Marcel Just, director of the Center for Cognitive Brain Imaging and author of the report to be released in the upcoming journal "Brain Research."

For the first time, the Carnegie Mellon study used brain imaging to document that listening to a call reduces the amount of brain activity associated with driving by 37 percent. This can cause drivers to weave out of their lane, based on the performance of subjects using a driving simulator.

Other distractions, such as eating, listening to the radio or talking with a passenger, also can divert a driver. Though it is not known how these activities compare to cell-phone use, Just said there are reasons to believe cell phones may be especially distracting.

"Talking on a cell phone has a special social demand, such that not attending to the cell conversation can be interpreted as rude, insulting behavior," he noted. A passenger, by contrast, is likely to recognize increased demands on the driver's attention and stop talking.

The 29 study volunteers used a driving simulator while inside an MRI brain scanner. They steered a car along a virtual winding road at a fixed, challenging speed. They were either undisturbed, or they were asked to decide whether a sentence they heard was true or false.

Just's team used state-of-the-art functional magnetic resonance imaging (fMRI) methods to measure activity in 20,000 brain locations, each about the size of a peppercorn. Measurements were made every second.

"The clear implication is that engaging in a demanding conversation could jeopardize judgment and reaction time if an atypical or unusual driving situation arose," Just said. "Heavy traffic is no place for an involved personal or business discussion, let alone texting."

The project was funded by the Office of Naval Research. Other members of the Carnegie Mellon research team included post-doctoral research associate Timothy Keller and research assistant Jacquelyn Cynkar.

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