Cell Phones Dangerous After You Hang Up

July 11, 2002 -- -- TESTING TESTING TESTING TESTING Researchers have found scientific evidence that driving while talking on your cell phone significantly reduces alertness and may pose a serious risk in traffic.

Researchers from Carnegie Mellon and the University of Rhode Island measured drivers' alertness while conducting cognitive tasks, like talking on a cell phone or remembering lists.

"There is a very substantial decrease in the amount of brain activity, the amount of neural activity allocated to driving, while you are simultaneously listening," said Marcel Just, a Carnegie Mellon professor.

Just's study used magnetic resonance imaging to measure subjects' brain activity while using a cell phone. According to the study, the amount of brain activity decreased 29 percent when participants were listening to a conversation.

"The fundamental implication is that engaging in a demanding conversation could jeopardize judgment and reaction time if an atypical or unusual driving situation arose," said Just.

It’s All in the Eyes

URI's Manbir Sodhi and Jerry Cohen designed a head-mounted, eye-tracking device that measures the position of a driver's eye. The device has two cameras: one that looks at the road and one that can measure 250 eye movements per second.

According to Sodhi, drivers' eyes move constantly when focused on the task at hand — driving — but when engaged in other cognitive tasks while driving, like changing a radio station or talking on a cell phone, those eye movements slow significantly. During cell phone conversations, the eyes stayed focused straight ahead and drivers experienced tunnel vision.

"You are not moving [your eyes] as much … You are keeping them straight ahead more than you would under quite normal conditions," Sodhi said.

And Sodhi found that the so-called tunnel vision does not end when the conversation does, perhaps because drivers are still thinking about their conversation.

Even the cell phone industry acknowledges the dangers of driving on the phone and promotes safe habits.