While engaged in the listening task, drivers simultaneously listening to sentences veered off the road and onto the shoulder almost 50% more often than those allowed to focus uniquely on driving. And all they had to do was steer the car forward: no cars veered into their lane, no children darted into the road, no construction site loomed up unexpectedly.
"Before we ever ran any of these studies, some thought, 'Well, these were two independent tasks, performed by two independent brain areas,' " Just says. But certain brain regions are very likely critical to both tasks, he adds, and the flow of traffic in the multi-tasking brain appears to have slowed as a result. "It can only do so much at a time."
Listening isn't so easy
People mistakenly believe that listening is a light burden and readily adjustable when competing demands crop up, Just says. But he believes that spoken language is neither simple to process nor easy to tune out.
"For a driver, it's insidious," he says. "You think driving is kind of effortless, chatting is kind of effortless, so what the heck. And you can combine them and, mostly, you're fine. But in hard driving, that can be a definite risk."
If listening is demanding, talking appears to be even harder, especially when the other person isn't in the car. In a study published in June in the journal Experimental Psychology, University of South Carolina psychologist Amit Almor put 47 subjects in a surround-sound console and had them detect visual shapes on a monitor or use a mouse to track a moving target on a screen.
When the subjects listened to prerecorded narratives, their attention to the visual task before them dipped significantly. But as they then answered questions about what they'd seen, or even just got ready to speak, their attention to the task on the screen didn't dip -- it plummeted.
"It has not anything to do with manipulating the phone or holding it," Almor says. "It's the attentional demands of conversation that matters." Those demands shoot up, he adds, when drivers expect to contribute to conversations.
Some researchers, in fact, fear that the new law may cause more traffic accidents, not fewer, because they envision more distractions for many motorists. When ring tones chime and drivers scramble to find their newly purchased headsets -- or, alternatively, scan the roadsides for police enforcing the new ban -- their attention, already stretched, will be further taxed.
Strayer suggests, too, that motorists who believe they're now safer because they're not using a hand-held may now spend more time on the phone in the belief that cellphones' safety issues have been addressed.
It's clear many drivers agree with Schwarzenegger's contention that the roads will be safer. Denise Spooner of Claremont says that although she has her doubts about other drivers, she's pretty sure that hands-free-calling-while-driving has made her a less-hazardous motorist. A stick-shift owner -- and a longtime user of headsets -- Spooner, a 52-year-old historian at Cal State Fullerton, says having both hands available for rapid response "makes the difference."
"What else," she asks, "could it be?"
--
melissa.healy@latimes.com
