We were both mildly curious about this speed demon, so we looked over into the other car. In the driver's seat was a young man - perhaps in his early or mid-20s - and in his hands was a Sony PSP.

For those who don't know, the PSP is a handheld video game system - a PlayStation for the palm of your hand - and this guy was playing it behind the wheel!

Every day, drivers like Mr. PSP head out on the road, distracted by cell phones, illegal in-car video systems and a variety of other techno-gadgets, all of which contribute to as many as half of the 6 million crashes reported in the United States annually, according to a recent study reported in the journal Neuron.

"Distracted driving," the category that encompasses these kinds of activities, is the reason given for 4,000 to 8,000 car crashes reported each day in this country, according to Vanderbilt University researcher Rene Marois.

The night that my fiance and I saw Mr. PSP, I rolled down my window and chastised him right there in the street. For the record, he denied that he was playing a video game and instead explained that he was watching a movie, but "not watching the screen." Still, watching anything other than the road while you're hurtling down the highway at 65 or - let's get real here - 80 miles an hour is dangerous.

That's because our brains aren't programmed to process images as quickly as we may think, Marois and her partner James Todd discovered. The pair used functional magnetic resonance imaging to monitor the brain activity of 20 patients who were then barraged with visual information.

While humans may see something, they need time to process the visual information, Marois and Todd found. "Whenever we pay attention to an object or a visual event, we actually need up to a second or half a second," the pair wrote in their Neuron article. "While our brain is busy processing one visual event, we may not be able to process other visual events that are going on in the visual world."

Information being processed by the human brain may "bottleneck," and that delay, which applies to non-visual communication like cell phones, too, can be critical behind the wheel, according to University of Utah psychologist David Strayer.

Strayer, who authored a recent study on the topic in the Journal of Experimental Psychology: Applied, asked participants to drive in a simulator while talking on their cell phones. He found that the reaction time of drivers who spoke on the phone was slowed about 20 percent and hypothesized that talking on a cell phone actually created a "virtual reality" between the two people conversing. Instead of dealing with the real, physical world around them, drivers' attention was diverted to the world of their conversations, leading to an increased risk of accident.

I guess it might be time for me to hang up and drive.

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