Listening on a cell phone can make a driver as dangerous as a drunken one

Listening on a cell phone, even with a headset and free hands, can make a driver as dangerous as a drunken one, a new study suggests. Researchers have previously explored this territory, but Carnegie Mellon University scientists tried a new tack: they looked at the brain. They used brain imaging to show that listening to a cell phone significantly reduces the brain activity that occurs during undistracted driving. This drop in brain function increases driving mistakes - such as weaving out of the lane or hitting a berm on the shoulder of the road.

In the study, to be published in the journal Brain Research, 29 drivers, ages 18 to 25, used a driving simulator while inside a sophisticated brain scanning machine, called functional MRI. They steered a car along an empty but winding two-lane highway at a fixed speed of 43 miles per hour. Then, they repeated the simulation while listening to statements of general knowledge. After each statement, they had five seconds to say whether it was true or false. The MRI measured second-by-second changes in activity in 20,000 brain locations. It showed that listening caused a 37 percent decrease in activity in the parietal lobe, which controls skills involved in driving. Activity also decreased in the occipital lobe, the center of visual information processing. At the same time, listening increased activity in the area of the cortex that is linked to language.