Mr. Pence is well aware of how destabilizing cellphones, iPods and hand-held video game players can be to family relations. "I see kids text under the table at the restaurant," he said. "They don't teach them etiquette anymore.” Some children, he said, watch videos in restaurants.

"They don't know that's the time to carry on a conversation," he said. "I would like to walk up to some tables and say, 'Kids, put your iPods and your cellphones away and talk to your parents.'" But even he has found that enforcing rules is harder than might be expected. He now permits Savannah to send text messages while watching TV, after he noticed her using a blanket over her lap to hide that she was sending messages to friends. "I could have them in the same room texting, or I wouldn't let them text and they would leave," said Mr. Pence of his children. "They are good kids, but you want to know what they are up to."

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In fact, texting appears to be easier than talking for some cellphone users, providing yet another distraction for them inside their cars. Mr. Blanton at Vanderbilt, like many of his peers, texts his mother and friends even when both of his hands should be on the steering wheel. "I can text without looking at the phone," he said. "It's definitely not safe. Sometimes I'll look up and I don't remember where I've been driving."