Research suggests that drivers spend around 70 percent of their time mind wandering while behind the wheel.
The researchers are unable to confirm whether mind wandering is hazardous, but they note that lack of driver awareness is a key risk factor for motor vehicle accidents.
Study co-author Carryl Baldwin, of George Mason University in Fairfax, VA, and colleagues recently reported their findings in the journal Frontiers in Human Neuroscience.
Every year, more than 2 million people are injured and 32,000 people are killed in motor vehicle accidents across the United States.
Distracted driving - defined as any activity that deflects attention from driving, such as texting or talking to passengers - is considered a major player in motor vehicle accidents. In 2015, distracted driving was involved in around 391,000 injuries and 3,477 deaths in the U.S.
Mind wandering - which is described as spontaneous, internal thoughts that divert our attention away from a primary task - can be considered a distraction. However, unlike texting, it is a distraction that cannot always be avoided.
For their study, Baldwin and colleagues sought to determine how frequent mind wandering is during driving, and whether it should be investigated as a potential driving hazard.
How often do drivers' minds wander?
To reach their findings, the researchers asked nine adults to participate in a driving simulation task for 5 consecutive days.
On each day, participants engaged in two 20-minute driving simulation sessions, which involved driving down a straight, repetitious highway at a consistent speed. These sessions were designed to replicate a commute to work and back.
Between each of these "commutes," participants were required to complete a written test known as the Sustained Attention to Response Task (SART).
"The SART was included in the experiment to roughly simulate cognitively demanding office work, which could potentially influence participant performance or mind wandering frequency on the second drive of each day via a depletion of executive resources that would otherwise maintain attention towards the primary task," the researchers explain.
"However," they add, "the purpose of including the SART wasn't to examine the effect of the SART per se, but rather to ensure that enough mind wandering instances occurred throughout the course of the study for comparison of mind wandering and on task states."
During each driving simulation session, the brain activity of each subject was measured using electroencephalogram, as a means of identifying electrical patterns associated with mind wandering.
As an additional measure of mind wandering, the participants heard random buzzers during each driving simulation session. When they heard the buzzer, they were asked to indicate whether their mind had been wandering just before the buzzer sounded, and whether they had been aware of their mind wandering.
The researchers found that participants reported mind wandering for around 70 percent of their time behind the wheel, particularly during their "commute" home from work.
On average, participants reported being aware of their mind wandering just 65 percent of the time.
Is mind wandering a driving hazard?
Additionally, the researchers were able to identify distinct brain patterns related to mind wandering in the subjects as they completed the driving tasks.
Interestingly, these brain patterns were also associated with reduced receptiveness to external stimuli, which suggests that mind wandering might impact concentration during driving.
Still, the team is unable to confirm whether mind wandering is dangerous during driving, but they believe that this possibility should be investigated in future research.
"Mind wandering may be an essential part of human existence and unavoidable. It may be a way to restore the mind after a long day at the office," says Baldwin. "What we are not sure about yet, is how dangerous it is during driving. We need additional research to figure this out."
If mind wandering is proven to be a driving hazard, Baldwin says that there are a number of strategies that could help to address the problem.
"In terms of improving safety in the future, one option could be autonomous transport systems, like self-driving cars, that allow people's minds to wander when it is safe to do so, but re-engage when they need to pay attention," she notes.