The higher rate of motor vehicle crashes involving teenage drivers has been attributed to their general “recklessness” and inexperience behind the wheel. A new study, however, points to another possible factor, one involving a particular feature of the adolescent brain: a working memory that is not yet fully developed.

“We found that teens who had slower development in working memory were more likely to report being in a crash,” said Elizabeth Walshe, the study’s lead author and a postdoctoral researcher in injury prevention at the University of Pennsylvania, in a released statement.

She and her colleagues say their findings, which were published last Friday in JAMA Network Open, suggest that assessing the working memory of individual teens could be an important addition to the graduated driver licensing programs that states have implemented in recent years for adolescent drivers.

“There is considerable variation in working memory development during the teen years, and some teens may not be as ready to drive on their own without additional assistance,” said Daniel Romer, the study’s senior author and research director of the Annenberg Public Policy Center at the University of Pennsylvania.

“If our findings hold up in larger samples with diverse youth, we will need to start assessing cognitive ability, such as working memory, to see if some adolescents are less ready for independent driving,” he added.

Motor vehicle crashes are the leading cause of injury and death among 16- to 19-year-olds in the United States. Six teens die every day on American roads.

Study details

For their study, Walshe, Romer and their co-authors analyzed data from participants in the Philadelphia Trajectory Study, a longitudinal study that tracked risky behavior in Philadelphia youths over a multiyear period. The young people entered the study in 2004 when they were 10 to 12 years old, and were repeatedly assessed until 2014.

One of the factors measured during those assessments was working memory, a form of short-term memory that “allows for in-the-moment monitoring, updating, and planning,” as the authors of the current study explain in their paper.

Because driving is a complex task that requires people behind the wheel to pay careful attention to the ever-changing environment through which their vehicle is moving, working memory is crucial for safe driving, the researchers stress.

The original Philadelphia Trajectory Study involved 387 young people. In 2015, Walsh, Romer and their colleagues invited all of the participants to take part in a follow-up survey about their driving experiences, including whether they had ever been involved in a crash. About a third — 118 — agreed to take the survey. Of those, 84 were found to have a driver’s license and were included in the current study’s analysis.

Key findings

Twenty-five of the 84 survey respondents with a driver’s license — almost 30 percent — said they had been involved in a crash as a driver. Most — 18 — reported a single crash, although four of the young people reported two crashes, and three reported three or more crashes.

The most common reported reckless driving behavior was ignoring speed limits. Only 32 percent of the survey’s respondents said they had never done that. The least-reported reckless behavior was driving after consuming alcohol, which almost 86 percent of the young people said they had never done.

The young people who reported reckless driving were the most likely to report having been involved in a crash. Age, gender and years driving were not, however, correlated with crashes.

The researchers then looked for an association between the results of the young people’s working memory assessments with their reported record of crashes. They found one. The youths in the study whose working memory had developed the slowest — whose growth in this cognitive ability was less-than-average — were significantly more likely to have been involved in a crash while driving.

Those who had exhibited a greater-than-average growth in working memory were, however, significantly less likely to report being in a crash.

Those findings held after adjusting for alcohol and marijuana use.

Limitations and implications

The study has important limitations. First, the number of participants was small, which limits the power to detect associations. In addition, the participants’ crash history was self-reported and, therefore, may or may not have been entirely accurate.

Still, other studies — ones in which teenagers were tested on driving simulators — have linked a lower capacity for working memory with a greater likelihood of reckless driving and crashes. Researchers have also found that variability in working memory capacity during adolescence is tied to impulsivity and substance use, known risk factors for reckless driving.

Together, these findings help to explain an important point that Walshe and Romer make in their paper: While crash statistics “indicate that risk is high in young drivers, most young drivers do not crash.”

The current study, they stress, “builds on the scientific foundation for evidence-based guidelines for the counseling and management of young drivers by addressing individual variation in development.”

“Encouragingly, these findings suggest that any interventions that could improve or enhance [working memory] development during adolescence may offer a novel way to reduce the risk” of crashes,” they add.

FMI: You can read the study in full on JAMA Network Open.