Development of the adolescent brain may play a critical role in involved in motor vehicle crashes


Research into why adolescent drivers are involved in motor vehicle crashes, the leading cause of injury and death among 16- to 19-year-olds in the United States, has often focused on driving experience and skills.

But a new study suggests that development of the adolescent brain may play a critical role in whether a teenager is more likely to crash.

The study finds that slower growth in the development of working memory is associated with motor vehicle crashes, which points to cognitive development screening as a potential new strategy for identifying and tailoring driving interventions for teens at high risk for crashes.

The study, led by researchers at the Annenberg Public Policy Center of the University of Pennsylvania (APPC) and Children’s Hospital of Philadelphia (CHOP), is the first longitudinal study of working memory development in relation to vehicle crashes.

The paper “Working Memory Development and Motor Vehicle Crashes in Young Drivers” was published today in JAMA Network Open.

The research examines data from 118 youth in Philadelphia who were part of a larger group that participated in a six-wave survey from when they were 10- to 12-year-olds, in 2005, until they were 18- to 20-year-olds, in 2013-14.

The survey measured working memory development, as well as associated risk-related traits and behaviors.

This group later participated in a follow-up survey on driving experience.

“We found that teens who had slower development in working memory were more likely to report being in a crash,” said the lead author, Elizabeth A. Walshe, Ph.D., who is a postdoctoral fellow at the Annenberg Public Policy Center and at the Center for Injury Research and Prevention at CHOP.

Driving and working memory

Working memory, which develops through adolescence into the twenties, is a frontal lobe process associated with complex, moment-to-moment tasks essential to driving.

“Safe driving involves scanning, monitoring, and updating information about the vehicle and environment while managing multiple subtasks (e.g., adjusting speed, steering, in-vehicle controls) and distractors (e.g., peer passengers and cell phones),” the researchers said in their paper.

All of these tasks challenge working memory, especially when a young driver has not yet fully learned to automate many basic driving routines.

Adolescent drivers have the highest rate of crashes, injuries, and mortality.

While poor skills and inexperience explain some of the risk shortly after a new driver receives a license, crash risk is inversely related to age during the early years of driving.

In other words, among equally new drivers, those who are 17 years old have a higher crash rate than those who are 20 years old, which suggests a possible developmental link.

“Not all young drivers crash,” Walshe said. “So we thought, what is it about those who are crashing? It could be related to variability in working memory development.”


Prior research has shown a link between lower working memory capacity and reckless and inattentive driving, crashes, and poor performance on simulated driving tasks.

For the current study, the researchers recruited participants from the Philadelphia

Trajectory Study, a broad six-wave study conducted by researchers at APPC and CHOP. Across seven years – when the adolescents were 11-13 years old to 18-20 years old – this study measured the change in working memory and other characteristics.

Subsequently, in 2015, 118 young adults, including 84 drivers and 34 non-drivers, took the follow-up survey on driving. Among the drivers, 25 reported having a crash history and 59 reported no crash history.

The drivers who reported crashes and those who didn’t started from about the same point in working memory capacity though the trends diverged from there.

The researchers found that the relative growth of working memory was associated with car crashes within three years after starting to drive. Young drivers whose trajectory of working memory growth was less-than-average in the group were more likely to report being in a crash; drivers with greater-than-average growth in working memory were more likely to say they had not been in a crash.

The analysis controlled for other risk-related factors including reckless driving and drug use.

Driving crashes: “Predictable and preventable”

The researchers say the results have important policy implications.

While all 50 states have some type of graduated driver licensing (GDL) program that gradually lifts restrictions for young new drivers, the research suggests that individual assessments of adolescents’ cognitive development may play an important part, too.

“If our findings hold up in larger samples with diverse youth, we will need to start assessing cognitive abilities, such as working memory, to see if some adolescents are less ready for independent driving,” said Daniel Romer, Ph.D., research director of the Annenberg Public Policy Center and a senior fellow at the Center for Injury Research and Prevention at CHOP. “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.”

Flaura K. Winston, M.D., Ph.D., founder and scientific director of the Century for Injury Research and Prevention at CHOP, said that enabling teens to become safe drivers is a health concern for physicians. Prior research has focused on driving skills and experience, but this study examines cognitive development in typical adolescents and suggests that individual variation plays a critical role.

“This research points to the fact that crashes are predictable and preventable,” said Winston, who also is an APPC distinguished research fellow. “It focuses attention more on the role of the driver and the driver’s clinician. A clinician could identify teens who will be at an increased risk and use ‘precision prevention’ to tailor anticipatory guidance so that young drivers achieve independent mobility in a safe way.”

Precision prevention, Winston said, could provide different types of driver training or a release from driving restrictions at different times based on their development.

The researchers said that some form of standardized screening or testing during adolescence could determine which teens have slower development of working memory. “Ideally, we’d be able to offer interventions like driver training or technologies like in-vehicle alert systems to assist new drivers who need it,” Walshe said.

In addition to Walshe, Romer, and Winston, the study was conducted by Laura M. Betancourt, Ph.D., and Kristin Arena, B.S., at CHOP, and Atika Khurana, Ph.D., of the College of Education, University of Oregon, who is also an APPC distinguished research fellow.


A variety of affective factors influence teen decisions and behaviors, as Ronald Dahl explained. He began with what he called the health paradox of adolescence. Although adolescence is the healthiest period of the life span physically, a time when young people are close to their peak in strength, reaction time, immune function, and other health assets, their overall morbidity and mortality rates increase 200 percent from childhood to late adolescence. Many of the primary causes of death and disability in these years—which include crashes, suicide, substance abuse, and other risky behaviors—are related to problems with control of behavior and emotion.

The reasons why adolescents can have difficulty controlling their emotions and behavior are complex, and a thorough overview of decades of research on adolescent development was beyond the scope of the workshop.1 Instead, the focus was on identifying key insights that may have particular relevance to the problem of teen crashes and to use these insights as an entry point for exploring possibilities for improving the effectiveness of teen driving safety efforts.

A complex web of physiological, psychological, and environmental conditions contributes to an increase in impulsivity in adolescents and influences both decision making and regulatory functions that affect driving as well as other adolescent behaviors

Indeed, a hallmark of this stage of life, not only in humans but also in other mammals, is the tendency toward increased risk-taking and novelty-seeking, as well as an increased focus on social context (Romer, 2003Lerner and Steinberg, 2004).

These characteristics foster the development of independence at the same time that they increase young people’s exposure to risk, and it is important to note that they involve both natural and adaptive processes, even though they can have very negative results.

As might be expected, the onset of puberty plays an important role. As puberty begins, changes in the endocrine system can affect drives, motivation, mood, and emotion. This period is characterized by increased emotional intensity and changes in romantic motivation. It is associated with increases in risk-taking, novelty-seeking, and sensation-seeking, as well as an increased focus on social status.

These attributes can have significant effects on driving behavior.

Moreover, cognitive development occurs on an unrelated trajectory that is not complete until the early 20s—long after puberty is over. Thus, the capacity for planning, logical reasoning, and understanding the long-term consequences of behavior are far from fully developed during the period when most young people in America are beginning to drive.

Another key difference between adolescent and adult brains is in their capacity to manage multiple tasks at once.

The capacity known as executive function, which is the key to judgment, impulse control, planning and organizing, and attention—or, as it has been called, the CEO of the brain— is situated in the prefrontal cortex, which is still under construction during the teen years.

In the absence of stress and distraction, most teens function well, but this regulatory capacity can be easily overwhelmed by strong emotion, multitasking, sleep deprivation, or substance abuse (Luciana et al., 2005).

The particular risks posed to teen drivers by extra passengers, music, cell phones, and other sources of stimulation or distraction begin to make sense when this aspect of teen development is understood. Other specific perspectives on adolescents offer further insight.


Adolescents also differ in significant ways from adults in their approach to risk and decision making, as Julie Downs explained. She began by enumerating the primary factors that affect decision making in general:

  • knowledge of risks,
  • appreciation of the potential trade-offs between risks and benefits,
  • assessment of short- and long-term expectations,
  • focus on the most likely outcomes, and
  • perceived alternatives to taking the risk.

The conventional wisdom about teenagers’ risk-taking is that they both fail to appreciate the risks that face them and wrongly perceive themselves as invulnerable to risk in general. In fact, however, teens do not believe they are invulnerable.

Their perceptions of many risks are fairly accurate, and they actually tend to rate their overall risk of premature death as far higher than it actually is.

For example, while teens can estimate the likelihood of being arrested (less than 10 percent) or, among girls, becoming pregnant in the next year (6 percent) with fair accuracy, they estimate their risk of dying in the next year at 18.6 percent, while the actual risk is 0.08 percent. Teens can be overly optimistic in other areas. Nearly 73 percent, for example, predict that they will have a college degree by the age of 30, while only 30 percent actually achieve this goal.

The misperception that affects teens’ driving, which they share with adults, is a tendency known as the optimistic bias, or overconfidence in their own control over risk.

For example, while smokers of all ages know that smoking puts them at risk for lung disease and death, most believe their own risk is less than that of a typical smoker. What compounds this problem for teens, however, is their lack of understanding and inaccurate thinking about cumulative risk.

In other words, teens correctly assess the risk associated with any single car trip as relatively low.

However, each time the teen takes an uneventful drive, his or her perception of the riskiness of driving goes down while perception of the benefits goes up. While a teen driver may still acknowledge the overall risk, even after acquiring months of experience, he or she perceives a decline in the risk posed by any single driving trip.

The result is a teen who believes he or she can handle hazardous situations, is overconfident of his or her driving skills, and is decreasingly vigilant about safety. Since the teen is also less experienced and competent at the wheel than the average adult, the optimistic bias is particularly hazardous for teen drivers.


Adolescents are intensely attuned to social interactions with their peers, and Sara Kinsman and Joseph Allen provided two perspectives on the key ways in which these relationships influence behavior and increase risks for young drivers and their passengers.

Teens are focused on their peers for good reason, Kinsman noted, and she argued that learning to negotiate peer relationships is the most important developmental task that adolescents must accomplish. To complete the transition to adulthood, teens must learn to get along with, work with, live with, and care for their peers, and these relationships are integral to success in almost every aspect of life.

Kinsman explained that the collective process through which teens create their own culture is an important part of this task—and that it is not simply a matter of rebelling against adult norms and authority.

Reciprocity is an important part of this process, so it is important for young people to demonstrate that they are a part of the collective endeavor by emphasizing ways in which they are like other members of the group.

Issues of status, social groupings, and adherence to norms are all integral to this process.

Because these relationships and the teen’s place in his or her peer group are so important developmentally, the peer group can have as much influence on behavior as individual characteristics, such as gender, socioeconomic status, and family influences.

Peer interactions often make risky behaviors more likely. Kinsman presented data from a study by Mokdad et al. (2004), which demonstrated that teens typically initiate dangerous behaviors with peers—indeed, approximately 25 percent of all U.S. deaths are the result of activities that are initiated with peers during adolescence.

Joseph Allen amplified this point with a discussion of teens’ attitudes toward deviant or risky behavior.

He noted, as Ronald Dahl had as well, that teens are more prone to thrill-seeking than adults are, and that their quest to seem mature and to increase their autonomy can lead them to take risks.

Rates of deviance, Allen explained, increase dramatically beginning at about age 11, peak at around age 16, and then drop off gradually over the following 10 to 15 years. Several factors combine to make all teens vulnerable to negative peer influences.

Teens’ great need for social acceptance combines with inexperience in handling pressure from peers. Moreover, Allen explained, popular teens are more likely than so-called average teens to engage in risky behavior at younger ages, to increase that behavior quickly, and to sustain it (Allen et al., 2005).

Moreover, as Kinsman noted, popular teens are socially adept and have a skill set different from that of others.

They have a particularly strong influence on youngsters who are social followers—eager to improve their social status by association with more popular peers. Thus, in many cases, the teens in leadership positions are more likely to instigate risky behavior—but teens who are struggling socially may be more susceptible to negative influences.

Driving—the single activity that involves the greatest risks for the largest number of teens—can play an important role in peer interactions.

The ability to drive one’s friends around can allow teens to pursue important social goals, for example, by allowing them to demonstrate maturity, return favors that others have offered, enhance their status, reinforce membership in a group, or host the social event that a group car trip can be.

The key point in terms of driving safety is that when driving with peers, teens are undertaking two separate, challenging, and complex tasks: they are keenly attuned to the behavior of and interactions among their peers while also operating the vehicle and attending to road and traffic conditions. From a developmental perspective, Kinsman argued, it is unrealistic to expect teens to tune out their peer passengers and give their full attention to the task of driving.

Allen described the situation in a car full of teenagers as “the perfect storm,” because four elements come together in that situation: peers who may value risky behavior, teens who need social acceptance, the likelihood that the riskiest teens will be the loudest, and all teens’ relative lack of immunity to peer pressure. At the same time, the teen who is driving cannot easily see the faces of the passengers, which increases the stress of staying attuned to the social dynamics, yet it is the driver who is primarily responsible for the safety of the situation.

Allen argued that it may be possible to harness peer influences in positive ways if strategies can be found to link responsible driving with attributes or rewards that teens value.

For example, teens value both self-confidence and skill, and they also value money and material goods.

Thus, a program that took these values into account by offering rewards for demonstrating responsible driving skills in specific ways – such as driving for a certain period without any violations or passing a series of tests – would have the benefit of meeting teens on their own terms.

More information:JAMA Network Open (2019). DOI: 10.1001/jamanetworkopen.2019.11421

Journal information: JAMA Network Open
Provided by University of Pennsylvania


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