In Brief: The Quirky Brain: Why cell phone conversations distract drivers

Harvard Mental Health Letter

Roughly eight in 10 Americans who own cell phones say they talk on them while driving. The results can be disastrous, causing motor vehicle accidents and deaths. About one-third of U.S. traffic accidents each year (about 1.6 million) are attributed to people talking on cell phones.

But many cell phone users remain skeptical that they might be endangering themselves or others. After all, why would talking on a cell phone in a car be any more distracting than talking to a passenger in the next seat? Studies suggest several possible reasons.

One study using a driving simulator found that drivers conversing by cell phone were more likely than those talking to passengers to drift between lanes and to miss an exit they were instructed in advance to take. When the researchers analyzed the complexity of the conversations in this study, they found that drivers and passengers tended to modulate their speech in response to external traffic cues. For example, they stopped talking when a traffic problem developed, or the passenger would offer advice to help the driver navigate. Conversations taking place by cell phone, on the other hand, did not vary much in response to changing traffic conditions (perhaps no surprise, because only the driver was actually aware of what was happening on the road).

Some drivers have switched to hands-free cell phones in an effort to eliminate the physical distraction of trying to hold onto a cell phone while steering the car. But a review of studies concluded that hands-free cell phones are just as distracting as handheld models. One study found that any cell phone use caused impairments similar to those observed in drunk drivers.

And while people like to think they can multitask, cognitive research suggests that the brain tends to focus on one major activity at a time, while slowing the processing of other external cues. That is why talking on a cell phone may cause "inattention blindness." In any event, the research provides an important reminder to all drivers: hang up and drive.

Ship AN. "The Most Primary of Care — Talking about Driving and Distraction," New England Journal of Medicine (June 10, 2010): Vol. 362, No. 23, pp. 2145–47.

Strayer DL, et al. "A Comparison of the Cell Phone Driver and the Drunk Driver," Human Factors (Summer 2006): Vol. 48, No. 2, pp. 381–91.