The moment of a car crash is the result of thousands of split-second decisions gone wrong: overlooking a deer lurking on the side of the road, or slamming on the brakes at the wrong time. Those instincts are honed through hours spent behind the wheel, but new research in JAMA Internal Medicine suggests that they’re also linked to brain development, which could explain why some teenagers get into more car crashes than others do.
The paper, released Friday, suggests that this disparity could come down to differences in working memory.
Already, car crashes are the leading cause of death for teens in the US. It’s easy to pin that on reckless driving and less experience on the the road, but more recent research suggests that there’s more going on.
The scientists behind this new paper report that teens who develop working memory skills at slower rates are more likely to get into car crashes than those who develop at the average rate.
Elizabeth Walshe, Ph.D., a post-doc at the University of Pennsylvania and the study’s lead author, tells Inverse that brain development may play a major role in how we teach teens to drive in the first place. Time behind the wheel is important, but testing working memory skills may reveal more about true driving ability.
“If working memory was screened routinely, it may be possible to identify teen drivers who are at greater risk for crashes based on their rate of development,” she says.
Working memory is believed to be important to driving skills because it falls under the umbrella of executive functions. Executive functions are basically the higher-level thinking processes that allow us to manage complex tasks, plan ahead, and think before we act. In teenagers, though, executive function is still developing. Not having decision-making skills fully online does have benefits, as impulsive decisions can lead teens to experiences and lessons that they benefit from later in life.
But it’s not great for driving skills.
In a 2017 review paper, Walsche noted that younger drivers with lower levels of executive function make more mistakes, drive more recklessly, and have higher risks of crashing. But in this study, she zeroed in on why she suspects the crucial process comes down to working memory: because it helps us multitask.
“Working memory is important for attending to the task at hand and processing information in the moment, as well as managing multiple sub-task demands,” explains Walshe.
Working memory is the process that allows you to execute the basic actions of driving — steering, braking, and accelerating — while you’re also watching for swerving lunatics or remembering which exit to take. Essentially, driving safely is about multitasking in the safest way possible.
Usually, working memory develops on a linear trajectory: It gets better as a teenager gets older. That development seems to plateau “as late as the mid 20s or even 30s,” notes Walsche, though scientists haven’t really pinned down an exact age when working memory peaks. But the rate at which working memory develops during teenage years seems to be particularly important for driving skills.
Walshe saw this when she followed 118 teens for seven years, from when they were 11 to 13 to when they were 18 to 20. At each point, they conducted surveys that measured working memory over time and had the teens report how many car crashes they got into when they reached driving age.
Over that period, the teens who developed working memory skills more slowly than average ended up in more car crashes. Those who developed working memory skills more quickly than average, on the other hand, were less likely to report being in a car accident.
Interestingly, all of these drivers had been on the road for the same number of years, showing that it’s not just time in the car that leads to fewer accidents, it’s also how the brain is developing during those hours behind the wheel.
This, as Welsche notes in the paper, gets to an important idea: Though car crashes are a leading cause of death for teenagers, most teen drivers don’t actually crash. But finding patterns that explain which drivers do get into accidents might provide a way to build in extra protections.
In the future, driver’s ed may focus a little less on hours in the car, and a little more on how the brain is actually developing while driving circles around the neighborhood.
Design, Setting, and Participants: This prospective cohort study used data from a longitudinal cohort of 118 community youth in Philadelphia, Pennsylvania. Working memory and other risk factors were measured annually from age 11 to 13 years (prelicensure, in 2005) to 14 to 16 years (in 2009), and again at 18 to 20 years (in 2013). In 2015, a follow-up survey of driving experience identified 84 participants who had started driving. Latent growth curve modeling was used to examine the association between variability in the baseline (intercept) and developmental trajectory (slope) of WM and the crash outcome.
Main Outcomes and Measures: Self-reported crashes were the primary outcome. Variability in the relative growth of WM development along with traits and behaviors associated with risky driving were assessed.
Results: Of 84 participants (39 [46%] male; mean [SD] age, 20.46 [1.09] years), 25 (29.8%) reported they had been involved in at least 1 crash. Controlling for other crash risk factors, the model indicated that variation in the linear slope of WM growth was inversely associated with reporting a crash (b = −6.41; SE = 2.64; P = .02). Crashes were also associated with reckless driving behavior (b = 0.40; SE = 0.18; P = .03). Variation in the intercept of WM was not associated with crashes (b = −0.245; SE = 0.67; P = .72).
Conclusions and Relevance: The results suggest that a relatively slower WM growth trajectory is associated with young driver crashes. Routine assessment of WM across adolescence may help to identify at-risk teen drivers and opportunities for providing adaptive interventions (eg, driving aids or training) that can address limitations in WM-related skills that are critical for safe driving.