Talking and driving don't mix, researchers say

Last Updated: Thursday, January 18, 2007 | 5:47 PM ET

CBC News

Two researchers are presenting a study aimed at identifying the "bottleneck" in the brain that makes it hard for people to multitask as a reason to avoid talking on a cellphone while driving.

"Our new research offers neurological evidence that the brain cannot effectively do two things at once. People think if they are using a headset with their cellphone while driving, they are safe, but they're not, because they are still doing two cognitively demanding tasks at once," said René Marois, an associate professor of psychology at Vanderbilt University in Nashville, Tenn. 

Marois and Paul E. Dux, a postdoctoral research associate in the psychology department, tested people to see what happened when the subjects were asked to perform two tasks at once, a news release Thursday said.

"The neural response to the second task was postponed until the response to the first was completed." -Paul E. Dux

The second task was often postponed, said their research abstract, published in the journal Neuron on Dec. 20.  

"These results suggest that a neural network of frontal lobe areas acts as a central bottleneck of information processing that severely limits our ability to multitask," the abstract said.

The researchers asked the subjects to press an appropriate computer key in response to hearing one of eight possible sounds and utter an appropriate syllable in response to seeing one of eight possible images. 

The results show that "the neural response to the second task was postponed until the response to the first was completed," Dux said.

Responses were delayed when the two tasks were presented nearly simultaneously, Marois said. But if the individual had a second or more between the tasks, "we did not see this delay."

Neither man uses his cellphone while driving.

"I'm Australian, and it's illegal there, so I'm trained not to," Dux said.

Even if he could, he wouldn't. A second is "a long time when you're travelling at 60 miles per hour."