Image: Driver speaks on cell phone in Maryland
A driver speaks on his cellular phone while driving through traffic in Prince Frederick, Md.
By Jon Bonné
msnbc.com

We’ve all heard it before: Keep your eyes on the road and don’t get distracted by phone calls or your passengers. New research, though, is providing a more nuanced view of how we focus while driving and what can erode our ability to do it safely. Simple rules, it seems, don’t always work.

In a newly published study, Spanish researchers detail how they tested drivers’ responses while performing a range of tasks — not just talking on the phone, but speaking with passengers or performing a series of mental calculations. The idea was to measure drivers’ overall cognitive ability; in other words, how well did individuals drive while they were also focused on other things?

What the psychologists leading the study concluded was that while everyone has a finite amount of mental processing ability, individuals also have the ability to manage how it is divided from one task to the other.

So, a small task — chatting casually with a passenger, or a quick phone call — isn’t necessarily a big distraction if the driver is in a familiar location and in light traffic. But a more complex driving situation, such as busy city streets, requires more attention. Most drivers know that, of course, and will often be less likely to use a mobile phone or let their mind wander. Overwhelming external stimuli may be stressful, but they can also focus people on the task of driving their cars.

By contrast, a drive on a quiet country road or a rural highway can be a problem because the driving task is not mentally engaging, leaving the driver’s mind to wander and lose focus. In that case, more external stimuli — talking to a passenger or listening to some music — might help to keep the driver’s brain engaged.

Nor are external tasks the only thing that can affect an individual’s ability to drive, according to the study, which appears in a June issue of the Journal of Experimental Psychology. Internal mental tasks — doing quick calculations or trying to remember something that once happened to you — also have an effect.

Attentive drivers, then, must be able to properly distribute their attention at any given time between the road outside, any distractions inside the car and even their own thoughts.

That amounts to what study co-author Luis Nunes of Spain’s national traffic agency, the Direccion General de Trafico, describes as “a process of cognitive management,” determining what’s most important at any given moment and being able to shift your actions to adjust for the changing levels of driving difficulty.

When a driver feels overwhelmed, it’s often because he isn’t able to change focus quickly enough from one task to another.

“Attention is really an active process,” says Nunes. “It will depend very strongly not only on the things that are going around him, but also on the priorities he has assigned on the tasks he is doing.”

How drivers were tested
Nunes and the other researchers measured the responses of 12 volunteer drivers — six men, six women — on an uncrowded Spanish highway outside Madrid. After letting them get used to the test car, a Citroen, the scientists threw a series of distractions at them as they drove: having a phone conversation; speaking with a researcher sitting in the car; listening to audio instructions and repeating them back; recalling specific details from memory; even doing conversions in their head between euros and Spanish pesetas.

All the while, a special optical tracking system monitored the drivers’ eye movements and recorded how often they would scan the road outside and look at the speedometer or the rear-view mirrors. Spotlights were also flashed occasionally in a driver’s field of vision as a signal to press a button near the steering wheel.

Overall, the study found the distractions could reduce drivers’ ability to detect changes on the road by up to 30 percent. They also determined that “endogenous” behavior — something that occurs in drivers’ minds, like complex thought, was as distracting as “exogenous” behavior, an external distraction like a conversation or a phone call.

Why our minds wander
Avoiding “endogenous” behavior may not be easy; there is a certain, inevitable tendency to let one’s mind wander when engaged in a familiar or routine activity. And as people become more experienced drivers, they begin to see driving as routine and grow comfortable with what remains a fundamentally risky behavior. Each time we arrive safely, we reinforce our belief that what we’re doing is safe until we begin to take it for granted, or so argues psychology professor E. Scott Geller, author of “The Psychology of Safety.”

“We get to our destination safely, yet we got there by at-risk behavior,” says Geller, who runs the Center for Applied Behavior Systems at Virginia Tech. “We keep getting away with it.”

The more familiar driving becomes to us, the more confident we feel about our ability to take on other tasks while we’re behind the wheel. And because driving skills are largely repetitive, we tend to lose concentration. That, Geller suggests, is why you might end up driving yourself toward work on the weekend or inadvertently turning onto your street when you meant to stop by the grocery store first.

Geller agrees that the sense of familiarity creates an extra risk behind the wheel.

“Cognitively we put the driving task in automatic mode because it is pretty simple usually,” Geller says. “When it’s in automatic mode, you’re not prepared for the unexpected.”

Rethinking safety rules
The Spanish study’s conclusion that thoughts can be as distracting as external actions suggests that some of the seemingly straightforward rules about safe driving aren’t that simple: While talking on the phone as you drive obviously poses a greater risk than not talking, a short call to say you’re on your way may provide far less distraction than a detailed conversation with someone sitting next to you in the car.

And whether you use a hands-free device may be less important than what you’re actually saying. “Perhaps it’s not a big deal to say to someone, ‘OK, I’m arriving late, wait for me half an hour,’” Nunes says. “But if you are a salesman or are having a complex negotiation on the phone with a customer this may lead you, perhaps, more easily to an accident.”

In addition, a speaker or a headset may actually prompt drivers to stay on the phone longer and have more complex conversations because they think they have taken steps to simplify the task.

And it’s not just phone calls. Any kind of complex behavior or thought can be distracting while you drive, the study found, even something like rehearsing a presentation you have to give at work. More specifically, productive processes — thoughts that require mental output — are more taxing to the driver than receptive ones, which simply require absorbing information.

Thoughts that require visualizing other spaces also can be distracting, especially if it requires visualizing motion, which can clash with the motion of the car. For example, Nunes says, trying to think about navigating your way through a complex road map may require a lot of effort if you think about it in terms of motion. You may be better off trying to visualize your path as a still image.

Even more distracting can be any mental activity with emotional impact — an argument with a passenger or anxiety over a forthcoming date.

And when it comes to conversations, there is a major difference, Geller points out, between chatting with a passenger and speaking on the phone. A passenger sees most of what a driver sees and can stop in mid-conversation if a road hazard appears. Someone on a cell phone only knows if you tell them.

“People can carry on very good conversations in a car. That’s not the problem,” Geller says. “The problem is using your resources when you need them, and the other person on the cell phone can’t tell when that’s needed.”

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