The Real Risk of Driving While Using Your Phone

A study shows why no one should get too comfortable on the road.

Posted Jun 10, 2014

Oleg Mikhaylov/Shutterstock

The message that smart phones can cause real problems for drivers is finally gaining traction. Texting while driving, as we now know, is extremely dangerous because it requires you to look away from the road—and it soaks up precious mental resources. Even talking on the cell phone can be dangerous.

But if it is so obvious to nearly everyone that using cellphones while driving is dangerous, why do so many of us continue to do it? And why do so many people (mistakenly) think that they are actually good at multitasking while driving?

This question was addressed in an interesting study by Nathan Medeiros-Ward, Joel Cooper, and David Strayer in the June, 2014 issue of the Journal of Experimental Psychology: General

As they point out, recent theories of attention suggest that when we perform complex tasks, we use two circuits of behavior: One circuit focuses on task performance; the other on the strategy for the task we are performing. When driving, the lower-level circuit (called the inner loop of attention) is involved in aspects of driving like keeping the car in the proper lane. The higher-level circuit (called the outer loop of attention) is involved in aspects of driving like dealing with unpredictable elements such as cars, wind, and pedestrians). Another example: When using a computer, the inner loop controls the typing of letters, while the outer loop controls your selection of words for a sentence.

To explore these aspects of attention, the researchers had participants drive in a simulator.  Participants were driving down a straight (virtual) highway. The difficulty of the task was manipulated by changing the wind—the more unpredictable the wind, the harder it was to keep the car in a lane. The researchers also manipulated the complexity of a second task that participants had to perform.  The secondary task interferes with the outer loop—the more complex the secondary task, the more the outer loop must focus on that task rather than watching the road.

Sometimes, participants did no secondary task. Sometimes, they performed a 0-back test in which they heard digits between zero and nine, and had to repeat back the digit they just heard. This task is fairly easy to do. Sometimes, participants did a 2-back test, in which they heard digits and then had to repeat the one they heard 2 digits ago—to keep on the task, they had to remember each new digit and then say back the one they heard two digits before. This task is hard.

Participants drove down the highway in each combination of wind, while doing either no second task, the 0-back task, or the 2-back task, as researchers measured how well the drivers were able to stay in their virtual lane.

When participants did no secondary task at all, they were equally good at staying in their lane, regardless of the level of wind. When the wind was highly unpredictable, participants fared much worse as the secondary task got harder. That is the typical finding in multitasking.

Interestingly, when the wind was only moderately unpredictable, people's driving was not strongly affected by the secondary task—they were reasonably good at staying in their lane regardless of how difficult the secondary task got. And when the wind was highly predictable, participants actually got better as the secondary task got harder.

What is going on here? 

When driving conditions are very easy, our inner loop of attention guides our driving and our outer loop has little to do—so it tends to monitor how the inner loop is doing. Unfortunately, paying added attention to a skilled task can actually make performance of that task worse. (This is one reason why skilled golfers and tennis players say they struggle when they pay too-close attention to the mechanics of their swing.) So in this case, when conditions were steady, the complex secondary task occupied the outer loop, allowing the inner loop do its job without complication.

When the driving task is more difficult, though, the inner loop guides driving, while the outer loop handles the disruptions caused by the wind. In this situation, the two systems function well together.  But when the outer loop is kept busy by a difficult secondary task, it cannot monitor the unpredictable wind as carefully, and driving suffers.

What does this mean for driving?

Most of the time, driving is fairly easy, and there are few unpredictable events. As a result, most people actually drive reasonably well even while they are talking on the cell phone. Unfortunately, it is, by definition, impossible to know when unpredictable events will happen, and so when performance suffers, it can be disastrous. And that is why it is so important to avoid distracted driving.

Just because participants in this study actually improved when they were distracted is no excuse to multitask when you are on the road. Remember: The easy driving task in this study just required staying in a straight lane with no other cars, pedestrians, or wind.  Real driving has many more unpredictable aspects than that—and your outer loop of attention has plenty to do.

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