Texting isn’t like other kinds of driving distractions. It’s way more dangerous because it so encompasses our attention that it strips away an emergency "sixth sense" that alerts us when something is about to go wrong.
A new study from researchers at the University of Houston pits texting against two other kinds of distraction—emotional stress and plain-old daydreaming. It sent 59 people driving down the same stretch of (simulated) road four times, once on regular high alert, once each while being bombarded with either challenging or distressing questions, and once while they were texting. And texting—surprise—was by far the most distracting of them all.
Ioannis Pavlidis and his research team measured both the stress levels of participants and the effect of that stress on their driving, characterized by lane departures and swerving. In the case of emotional and cognitive stressors, driving actually got a little safer, with regard to baseline measurements: There were more involuntary jerks on the wheel, but their heightened stress state enabled the participants to better cope with them.
"This paradox suggests an effective coping mechanism at work, which compensates erroneous reactions precipitated by cognitive or emotional conflict," writes Pavlidis. "This mechanisms’ grip slips, however, when the feedback loop is intermittently severed by sensorimotor distractions."
Even more interesting is that these distractions didn’t make any difference when reacting to "startling events." This, posits Pavlidis, suggests that we can process these surprise events automatically, before the stressed, distracted parts of the brain have time to get involved.
Texting, on the other hand, short circuits everything. It is, says Pavlidis, "disruptive and dangerous, even in moderate amounts" because it knocks out humans’ last line of conflict resolution defense in the anterior cingulate cortex region of the brain.
Pavlidis says that the anterior cingulate cortex (ACC), a part of the brain that helps control autonomic functions like blood pressure and heart rate, as well as some higher-level brain functions, helps correct errors. In the case of driving, he believes that it notices the jitters caused by the stressors. These jitters make the driver jerk the steering wheel more than usual or hit the gas by mistake in urban areas, for example. The ACC corrects for this, probably by actually seeing your hands as you steer and noticing the errors. When this hand-eye feedback loop is interrupted by something like texting, "ACC filtering slipped, failing at times to counterbalance instinctive motor reactions and thus, resulting into occasional lane departures," writes Pavlidis.
So, while we are well equipped to deal with stressful distractions (and seem to perform better because of them—on paper at least), sensorimotor stressors like texting hijack our visual attention, and short circuit our safeguards, making it pretty much the most dangerous thing you can do while driving.
Maybe, then, those texting-while-driving laws, often ridiculed as nothing more than political attention-grabbers, have a place next to our existing distracted-driving laws after all.
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