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A 'Sixth Sense' Protects Inattentive Drivers, Except When They're Texting

Researchers find a weakness in the brain's excellent error-correction hardware.
May 13, 2016, 12:00pm

An obvious retort against anti-driving and texting laws is that there are in fact many different ways of being distracted while driving. Texting just happens to be a relatively new, high-profile example. This would then make such laws examples of "feel-good laws," a favorite right-wing dis against legislation that arguably has more impact on public sentiment than real-life.

A new study led by University of Houston computer science researcher Ioannis Pavlidis adds an interesting twist to this intuition. In comparing several different varieties of driving distraction, the researchers found that texting had the unique ability to strip away the brain's defensive "sixth sense," a reflexive mechanism that intervenes in cases where a jittery, distracted driver might otherwise drift into another lane or sail off some cliff at high speed.


In their work, Pavlidis and co. set about exploring three types of driving distraction: emotional distress, absent mindedness, and texting. 59 volunteers were tasked with driving the same simulated highway segment under varying conditions, with each making four drives in total. The first was under normal, "focused" conditions, while the second and third were made while being asked cognitively challenging questions and emotionally distressing questions, respectively. The final drive was while texting. The order of the drives was randomized.

"Texting is a well-known example of a secondary task antagonistic to driving; it is a sensorimotor stressor, where the driver needs to move her/his eyes and one hand between the car's controls and the smartphone all the time," Pavlidis and his team write. "Most other types of antagonistic stressors are cognitive or emotional in nature. There has been little work about the distracting effect of each stressor category."

All three distracted conditions resulted in "jittery" driving behavior, but only texting resulted in full-on dangerous lane deviations. Drivers being asked either set of questions were generally able to maintain a straight course or a course on par with "normal" driving conditions. In the study, stress was measured using nose sweat (basically) as an indicator, while driving performance was (obviously) quantified as veering off course to the left or right.


So, what's the difference between texting and zoning out? Shouldn't distraction be distraction?

Not quite. Pavlidis suggests that the reason for the differing degrees of distraction may trace back to a region of the brain known as the anterior cingulate cortex, or ACC. The ACC is a busy nook of brain tasked with low-level functions like regulating blood pressure, but also high-level stuff like reward anticipation, decision making, and emotions. At the fundamental root of all of these functions is theorized to be conflict resolution and error correction—a constant comparison of actual outcomes vs. expected outcomes that occurs subconsciously.

When an error occurs while driving, whatever the cause, the ACC starts lighting up. The result is physiological stress and a burst of fight-or-flight energy sent to the driver's arms. The result is jitteriness. Strong jitters pulling to the right or left are caught by the AAC which sends back error corrective signals. So, the driver is able to stay more or less on track.

The AAC relies on a closed corrective loop between the brain, hands, and eyes. To adjust for deviations, it needs to be able to see them. But the act of looking at a phone is enough to break this loop and head off any corrective action that AAC may otherwise deem necessary. Hence, the results of the study. As a (partially) visual distraction, texting is uniquely dangerous.

"Pure emotional and cognitive distractions, although `rattle' human physiology and spawn reactive motor responses, they are managed at a second level by a corrective mechanism, and the observable error effect is negligible," Pavlidis told me. "However, this correction works only as far as there is no physical distraction. If a physical distraction combines with a cognitive and/or emotional stressor, then all hell breaks loose, because the `rattling' system underneath is left unchecked for a moment."

The brain is very good at stuff, to the point of neurologically implementing an error correction loop, but technology still fights back.