In case you’ve missed it , talking on your cell phone while driving is pretty dangerous. Although distracted driving may be more dangerous than drunk driving, the campaign to raise awareness and create a stigma around cell-phone use during driving chafes against introspection. Despite a large and growing body of work suggesting that distraction from cell phone use impairs reflexes, obstacle avoidance, and attention to signs and traffic signals, many people feel like they can safely drive while on the phone.

Anecdotally, driving seems automatic, intuitive, and easy, especially if the route is familiar (which allows navigation to proceed implicitly in the habit-based caudate nucleus, instead of explicitly in the hippocampus). Unlike texting, (or eating or applying make-up), which draws the driver’s eyes away from the road and hands away from the steering wheel, cell-phone use (especially the hands-free variety) appears more insidiously impairing. This is because we usually realize when our eyes are drawn away, or our hands are occupied, but we don’t always realize when our attention has wandered, or we’re distracted. ­­

In general, people overestimate their ability to multi-task, which is why, for instance, you might type the word you meant to say, instead of the word you meant to type. Dr. David Strayer, whose lab has led work in the domain of multi-tasking and cognitive impairment, told me by email that the gap between cognitive impairment and self-awareness might be what makes changing policy difficult: “50% of drivers favor laws prohibiting talking on a cell phone while driving…[but]…these drivers want the laws to apply to other drivers. They are overconfident in their own driving (and multitasking) ability.”

This is perhaps why many states have yet to seriously legislate against hands-free cell-phone use, although texting is banned almost everywhere. If using a cell-phone while driving is so dangerous, is it the type of impairment that people are unaware of? Or do people realize they are impaired, but decide to drive while using cell-phones anyway?

A recent study, published in Psychonomic Bulletin and Review, by David Sanbonmatsu, David Strayer, and colleagues from the University of Utah, investigated whether people are aware of their impaired driving during cell-phone use. In the study, one hundred undergraduate students were recruited and assigned to one of two conditions: a cell-phone group, which spoke on the phone to a friend or family member for the duration of the driving tasks, and a control group, which only completed the driving tasks. The two groups completed the same series of driving tasks in a driving simulator.

Participants were required to drive as safely as possible, follow traffic laws, and stop for pedestrians and obstacles. Afterward, participants estimated the number and type of errors they committed, and rated both the safety of their driving and how capably they believed they could drive during other tasks (such as talking on a cell phone).

Talking on a cell-phone while driving is still unsafe: participants in the cell-phone group committed significantly more serious driving errors than participants in the control group. In the control group, the number of serious driving errors was negatively correlated with participant’s assessment of their driving safety. That is, the more errors participants in the control group committed, the less safe they rated their driving. In the cell-phone group, there was a positive correlation – participants with more serious driving errors tended to rate their safety as higher. This pattern of results was the same when participants were asked about their perceived ability to drive safely while distracted. Finally, participants in the cell-phone group were also far less accurate at remembering which serious errors they had committed.

Although not perfect, humans are fairly good drivers who, unencumbered by distractions, are aware when they screw up. In the control group, which focused on driving, participants committed fewer errors, remembered the errors they did commit, and rated their driving safety to match how they actually drove. By contrast, the cell-phone group committed more errors, did not remember which errors they committed, and had little idea how safely they actually drove. Distraction, it seems, turns ordinary drivers into zombie motorists.

This study illustrates the deceptiveness of cognitive impairment. In some cases, cognitive impairment is obvious (try a Stroop task, which we’ve covered before). More often, cognitive impairment is not obvious. We are often blissfully unaware that we have a blindspot in our vision, which our brain fills in; or that we miss obvious anomalies when we’re staring right at them.

Usually the stakes are quite low: Spotting these oversights while comfortably browsing the internet is interesting and amusing. But when the stakes are high, and awareness of cognitive impairment is low, it’s a recipe for disaster. Data from the study by Sanbonmatsu and colleagues suggest that cell-phone use while driving hits that not-so-sweet spot. Despite committing multiple serious driving errors (including failing to stop at a stop sign, or swerving off the road), participants who were speaking on their cell phones had little awareness of the errors they committed, or their unsafe behavior more generally.

So, next time you’re out for a spin and the phone buzzes, let it go to voicemail. Just because it seems like you can pay full attention to the road, you almost certainly can’t.

Reference for the article discussed in this post:

Sanbonmatsu, D. M., Strayer, D. L., Biondi, F., Behrends, A. A., & Moore, S. M. (2015). Cell-phone use diminishes self-awareness of impaired driving. Psychonomic Bulletin & Review.