Talking on a cell phone while driving is far more dangerous than chatting with a passenger in the vehicle.
A study detailed in the December issue of the "Journal of Experimental Psychology" says driving performance is significantly reduced while a driver is on a phone, even the hands free variety.
The study, done at the University of Utah tested 41 mostly young adult drivers with both sexes equally represented.
Researchers placed drivers in three situations.
Conversation with a hands-free phone, conversation in the car with another individual and no conversation at all.
In a simulator, subjects were presented some ordinary challenges, changing lanes and speeds, speeding up, slowing down and paying attention to other traffic.
Each driver was told to pull off the highway at a specific rest area and stop.
In every case, drivers engaged in a cell phone conversation drove significantly worse than drivers talking with passengers.
Those on phones were more likely to drift side to side and were four times more likely to miss pulling off the highway into the rest area.
Passenger conversation hardly affected driver attention at all.
Missing from the study is an exact reason why cell phone use has such a debilitating effect on driving.
Doctor Frank Drews led the study.
He says phone users may find it more difficult to hold in working memory the intent to stop or even turn in pre-planned areas.
He says conversation analyses showed when driving tasks became more difficult drivers tended to use simpler language, reducing the number of syllables-per-word.
The researchers noticed passengers tended to take an active role in supporting the driver point out surrounding traffic.
They suspect that shared resource may be helpful rather than a hindrance to the driver.
(Copyright 2008 by Newsroom Solutions)