Driven to Distraction

Driving and cell phones don't mix.

The Research Studies

cellphone-drivingCell phones may be convenient but there's one place they seem to do more harm than good - and that's behind the steering wheel. Psychological research is showing that when drivers use cell phones, whether hand-held or hands-off, their attention to the road drops and driving skills become even worse than if they had too much to drink. Epidemiological research has found that cell-phone use is associated with a four-fold increase in the odds of getting into an accident - a risk comparable to that of driving with blood alcohol at the legal limit.

But cell phones aren't the only cause for concern. A host of emerging, even more engaging and time-consuming in-car technologies, such as navigational displays and Internet browsers, although developed to make long commutes more productive, also present new challenges for drivers. Cognitive psychologists and human-factors engineers are teaming up to document how these new gadgets affect driving performance and traffic safety.

David Strayer, PhD, of the Applied Cognition Laboratory at the University of Utah has studied cell-phone impact for more than five years. His lab, using driving high-fidelity simulators while controlling for driving difficulty and time on task, has obtained unambiguous scientific evidence that cell-phone conversations disrupt driving performance. Human attention has a limited capacity, and studies suggest that talking on the phone causes a kind of "inattention blindness" to the driving scene.

In one study, when drivers talked on a cell phone, their reactions to imperative events (such as braking for a traffic light or a decelerating vehicle) were significantly slower than when they were not talking on the cell phone. Sometimes, drivers were so impaired that they were involved in a traffic accident. Listening to the radio or books on tape did not impair driving performance, suggesting that listening per se is not enough to interfere. However, being involved in a conversation takes attention away from the ability to process information about the driving environment well enough to safely operate a motor vehicle.

According to Strayer's laboratory research, cell-phone drivers were also more likely to miss traffic signals and often failed to see billboards and other signs. A special eye-tracking device measured where, exactly, drivers looked while driving. Even when drivers directed their gaze at objects on the road (during simulations), they still didn't "see" them because their attention - during a cell-phone call - was elsewhere.

Corroboration came from a 2003 Spanish study that found, in a rare experiment using drivers in real cars on actual highways, that complex phone conversations affected visual scanning and reduced a driver's ability to detect, discriminate among and respond to visual targets - by as much as 30 percent. In this study, by psychologists Miguel Angel Recarte Goldarecena, PhD, of the Universidad Complutense in Madrid, and Luis Miguel Nunes González, PhD, of Spain's Administration for Traffic Safety, found equivalent effects from hands-free phone and live in-car conversations. In a 2002 study, they had found that low-demand conversations could be held with no interference. They concluded that the complexity of the conversation was what compromised concentration, whether the driver talked by phone or to a passenger. Thus, distractions inside one's own head can be just as disruptive as environmental distractions.

Strayer and his colleagues compared data for hand-held and hands-free devices and found no difference in the impairment to driving, thus, they say, raising doubts about the scientific basis for regulations that prohibit only hand-held cell phones.

The Utah lab is also measuring the increased risk associated with cell-phone use relative to other real-world activities - most recently, alcohol consumption. Disturbingly, forthcoming research will show that talking on a cell phone (even hands-free) hurts driving even more than driving with blood alcohol at the legal limit (.08 wt/vol). When talking on a cell phone, drivers using a high-fidelity simulator were slower to brake and had more "accidents" than when they weren't on the phone. Their impairment level was actually a little higher than that of people intoxicated by ethanol (alcohol).

Why Does This Happen?

Strayer's lab is building a theoretical account for why cell phone use disrupts driving performance. So far, the evidence points to conversations forcing drivers to withdraw their attention from the visual scene.

Frank Durso, PhD, with Kerstan Mork and John Morris of Texas Tech University, are also attempting to define the nature of the distraction. Is it a specific cognitive function? Is it attention, a broader enabler of cognitive function? More concretely, is it a conflict between the mental image and the current situation, such as an "out-of-the-car" conversation that puts drivers somewhere else mentally? The answer could help policy makers determine how to suitably regulate these devices. With or without legislation, says Durso, it's important to raise drivers' consciousness about the dangers of distraction.

From Research to Real Life

First and most obviously, drivers can make themselves, their passengers and other people on the road safer by putting down their cell phones. The standard advice is park in a safe place to make or take calls; at the very least, pull over to the curb or a highway shoulder if phone communication is truly urgent.

Second, drivers should also be aware that whether a cell phone is hands-on or hands-free makes no difference in terms of mental distraction. According to the research, the mental activity of conversation, whether in person or over the phone, is what takes one's mind off the road. What happens in the head happens regardless of what happens with the hands.

Third, drivers tempted to talk on the mobile might ask themselves if they would drive drunk. If not, they should put down the phone.

Fourth, drivers can pay attention to the nature of distraction in the car - with heightened awareness that new devices aimed at a better driving "experience" can have unintended side effects. Multitasking in or out of the car has been shown in many psychological experiments to divide attention and limit working memory - both essential to safe driving. Especially in the car, drivers should aim for the thoughtful use of any new devices or gadgets.

Finally, drivers need to remember that warnings (and, in some localities, legislation) about cell-phones and driving are prompted by cross-sectional studies of drivers of varied ages, educational levels, and years of driving. Susceptibility to distraction while driving has nothing to do with smarts or skill. In fact, psychologist Durso and his doctoral student Andy Dattel point out that although experts can do many things automatically, detecting hazards is not among them. Thus, Durso says, "anything that disrupts resource management can have consequences even in experts."

Cited Research

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Strayer, D. L., Drews, F. A., & Johnston, W. A. (2003). Are we being driven to distraction? Public Policy Perspectives, Vol. 16, 1-2. (Published by the Center for Public Policy and Administration, University of Utah).

Strayer, D. L., Drews, F. A. & Crouch, D. J. (2003). Fatal distraction? A comparison of the cell-phone driver and the drunk driver . In D. V. McGehee, J. D. Lee, & M. Rizzo (Eds.) Driving Assessment 2003: International Symposium on Human Factors in Driver Assessment, Training, and Vehicle Design. Published by the Public Policy Center, University of Iowa (pp. 25-30).

Strayer, D. L., Drews, F. A. Crouch, D. J., & Johnston, W. A. (2005). Why do cell phone conversations interfere with driving? In W. R. Walker and D. Herrmann (Eds.) Cognitive Technology: Transforming Thought and Society (pp. 51-68), McFarland & Company, Inc., Jefferson, N.C.

Strayer, D. L. & Drews, F. A. (In Press). Multi-tasking in the automobile. To appear in A. Kramer, D. Wiegmann, & A. Kirlik (Eds.) Applied Attention: From Theory to Practice.

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American Psychological Association, February 1, 2006