There is considerable evidence that using a cell phone impairs driving ability. The research has even reached the popular consciousness: hosts of radio call-in shows ask cell-phone callers to pull over before making their comments; drivers give wide berths to people who are obviously talking while they drive.

All this knowledge begs the question: If drivers are aware of the dangers of cell phone use, can they compensate for their weaknesses and effectively negate any problems from driving with a phone? Mary Lesch and Peter Hancock had been part of a 2003 team that had found drivers reacted slower to a stoplight when distracted with a simulated cell-phone dialing task. In a new article, they took another look at the data from that study to see if they could answer this secondary question: can drivers effectively compensate for the distraction of a phone?

In the 2003 study, participants drove cars around an outdoor test track and were asked to stop as quickly as possible when a red light flashed outside the car. Their reaction time, stopping time, and and stopping distance were measured. To simulate using a cell phone, participants had to indicate whether a digit flashed on a small monitor inside the car matched a phone number they had memorized before the task began. Participants were slower to react and more likely to go through the red light when doing the cell phone task.

The same participants had also been asked to rate how confident they were about dealing with the distraction, but this data was not analyzed in the original study. In 2004, Lesch and Hancock returned to this data with a new analysis. They divided the respondents into two age groups, older and younger, and analyzed the data for men separately from women. They then looked at confidence levels and reaction time. Here is the result:

Drivers with high confidence are those who indicated they were “comfortable” or “very comfortable” dealing with the distraction while driving. Low confidence drivers rated themselves “uncomfortable” or “very uncomfortable.” The change in reaction time reflects how much slower a driver reacted to a traffic light when distracted compared to driving without a distraction—so a taller bar indicates poorer performance driving with a cell phone. If drivers were able to compensate for their weaknesses, we might expect that more confident drivers would show a smaller change in reaction time. This holds true for male drivers, but women—especially older women—tend to react just as slowly, whether or not they believe they are comfortable handling the distraction.

The participants were also asked to rate how demanding the task was, and women rated it as significantly less demanding than men—despite the fact that women’s overall performance was not significantly different from that of men.

Though they consider this research to be “exploratory” due to the small number of participants (36), Lesch and Hancock argue that these results suggest that individuals are unable to assess the danger of driving with a cell phone. A common argument against banning cell phone use while driving is that drivers are aware of the dangers and can use their judgment to decide when it’s safe to make a phone call. If nothing else, these results certainly call that line of reasoning into question.

Lesch, M.F, & Hancock, P.A. (2004). Driving performance during concurrent cell-phone use: are drivers aware of their performance decrements? Accident Analysis and Prevention, 36, 471-480