From Robin Marantz Henig in The New York Times:
In the last few years, 30 states have considered legislation to outlaw the use of hand-held cellphones while driving. Most have failed. But three states now have such laws. The most far-reaching, New Jersey’s, which went into effect this month, prohibits drivers from doing anything else – not just talking while holding a cellphone but restraining a pet, reading a map or eating a Krispy Kreme doughnut on the way to work. The ultimate antimultitasking law.
*****Still, in the long run, multitasking is what wastes time. Last year, psychologists at the University of Michigan reported that when they asked subjects to perform two or more experimental tasks – solving arithmetic problems, say, at the same time they identified a series of shapes – the frontal cortex, the executive function center of the brain, had to switch constantly, toggling back and forth in a stutter that added as much as 50 percent to the time it would have taken to perform the tasks sequentially instead of simultaneously.