Friends Don’t Let Friends Listen and Drive

I am an insatiable fan of public radio. But whenever my daily commute gets hairy—and I live in Chicago, where potholes swallow cars and lane markers disappear faster than self-respect at a bottomless mimosa brunch—I instinctively turn the radio off.

Distracted driving isn’t just about station-surfing or texting or wearing Google Glass. Conversation—speaking and listening—can be distracting.  We have a limited supply of cognitive resources like attention, research tells us. If we expend some on Terry Gross interviewing our favorite author, we’ll have less to work with as we merge across four lanes of traffic.

But does it matter just what we listen to? A team of researchers, led by Benjamin Bergen at the University of California, San Diego, has recently asserted that some topics—and not particularly anger-inducing or shocking ones—may especially interfere with our ability to drive.

According to one increasingly popular theory, we process language by mentally simulating the events being described. Talking about kicking a ball requires us to activate parts of the brain required to kick a ball; ditto for comprehending the ball’s trajectory. With this theory in mind, the researchers hypothesized that conversing about topics that employ our perceptual or motor systems—specifically, how things look, sound, or are performed—may interfere with our ability to look, listen, and drive.

In their study, participants sat behind the wheel of a driving simulator, asked to stay “a safe stopping distance”—approximately 40 meters—behind the car in front of them.

While driving, they also responded to true-false sentences. Some were the abstract, factual trivia you would expect: The capital of North Dakota is Bismarck or Entomologists are scientists who primarily study insects. But others involved performing detailed actions: To open a jar, you turn the lid counterclockwise or To balance on a soccer ball, you rotate your ankles inward. A third set involved visualizing objects: The letters on a stop sign are white or A postage stamp is bigger than a tea bag. Finally, to serve as a control, sometimes participants were simply told, Say the word “true” or Say the word “false.”

The lead vehicle was programmed to brake during some of these sentences, allowing researchers to measure how long it took participants to themselves brake, as well as how closely their following distance hewed to 40 meters. They found that, for all three of the sentence types, participants were slower to brake—by about three quarters of a second—than in the control condition. This is no surprise. Interestingly, however, differences within the three sentence conditions emerged when researchers looked at how well participants maintained the following distance. Sentences involving actions or visualizations—sentences predicted to interfere with the motor and visual skills necessary for driving—produced longer and more variable following distances. The researchers argue, “By contrast with braking at the sight of brake lights, maintaining a specific following distance is a higher order task, which requires heavier use of higher level visual and motor memory and planning.” That is, though any sort of language might impair something as basic as reaction time while driving, language that requires us to simulate seeing or hearing or doing disproportionately affects more complex parts of driving.

The researchers’ story is not airtight: participants were no better at maintaining the 40-meter following distance in the abstract trivia condition than in the control condition, which seems odd to me. Also, although the study controlled for the difficulty of the sentences, it did not control for their interestingness. Perhaps it was the novelty of the perceptual and motor sentences (and to my mind, balancing on a soccer ball is vastly more interesting than the capital of North Dakota) that distracted the drivers. But on the whole, the study tells me what I know already: my love of public radio would be best served by abandoning the harrowing roadways and commuting to work on the El.