Melinda Beck writes in the Wall Street Journal:
These findings, published in the journal Nature last week, underscore why people aren’t very good at multitasking—our brains are wired for “selective attention” and can focus on only one thing at a time. That innate ability has helped humans survive in a world buzzing with visual and auditory stimulation. But we keep trying to push the limits with multitasking, sometimes with tragic consequences. Drivers talking on cellphones, for example, are four times as likely to get into traffic accidents as those who aren’t.