Most of us are neither pilots nor astronauts. We are not trained to steer large hulks of steel and gasoline while manipulating small computers. So there’s something blindingly obvious about the risks of texting while driving. Yet research is beginning to show that driving while simply talking on a cell phone—including using hands-free technology--can prove dangerous，even deadly. 
    In late July，the Center for Auto Safety released hundreds of pages of a study that identified the cell phone as a serious safety hazard when used on the road. And though it’s impossible to accurately calculate how many car accidents nationwide are cell phone related, David Strayer, a psychology professor at the University of Utah，estimates that only 2％of people are able to safely multitask while driving. 
    Strayer, who for more than a decade has been studying the effects driving and cell-phone use have on the brain，says those 296 are probably the same people who would be really good fighter pilots. Rarities. Some of Strayer's other findings show that most drivers tend to stare straight ahead while using a cell phone and are less influenced by peripheral vision（周边视觉）. In other words，“cell phones，”he says，“make you blind to your own bad driving. 
    And even though the common assumption is that hands—free technology has reduced the more dangerous side effects of cell-phone use，a series of tests conducted by Strayer seems to indicate the opposite. A passenger acted as another set of eyes for the driver in the test and even stopped or started talking depending on the difficulty of conditions outside the car. Meanwhile，half the drivers talking on a hands-free phone failed bypassing（绕过）the rest area the test had called for them to stop at. 
    Part of the problem may be that when people direct their attention to sound，the visual capacity of their brain decreases，says Steven Yantis，a professor of psychological and brain sciences at Johns Hopkins University. It can be as if a driver is seeing the image in her head of the person she is talking to，there by decreasing her ability to see what’s actually in front of her.