It's not uncommon for people to zone out during a tedious day at work, a droning conversation, or other boring circumstances. A new study suggests that daily commutes can be added to this list, concluding that drivers spend a majority of their time daydreaming instead of focusing on driving when traveling a familiar route.

The study was recently published in the journal "Frontiers in Human Neuroscience." It was conducted by researchers from George Mason University, the University of Wisconsin-Madison, the statistical survey company Westat, and the National Highway Traffic Safety Administration.

The researchers note how driver inattention is often linked to crashes, and that this factor can occur in the absence of any distracting factors. They suggest that driving is a "highly overlearned task" for many people, with mind wandering more likely to occur during familiar tasks. The study sought to determine how frequently drivers' minds wandered when driving the same route repeatedly, as well as any driving behaviors linked with such daydreaming.

Nine volunteers from George Mason University were recruited to make the same monotonous 20-minute drive twice a day for five days. In each drive, they were instructed to stay in the right lane and maintain a speed of 65 miles per hour.

The conditions were designed to replicate a morning and evening commute. The simulated freeway was generally straight, with only four curves incorporated into the route. After completing the first drive, participants completed a response task to simulate the cognitive demands of a day in the workplace. They then completed another drive going the opposite direction on the same route.

Periodically, an auditory tone sounded and participants were asked to press a touchscreen button on a dashboard display to indicate whether they were on task or daydreaming. If they chose the latter, they were asked to report whether or not they had been aware that their mind was wandering.

In 70.1 percent of the prompts, participants reported that they had been daydreaming when the tone sounded. Participants said they had been aware that their mind was wandering in 65 percent of these incidents.

While there was no significant deviation in the frequency of daydreaming as the study progressed, mind wandering was more likely to occur on the second drive of the day. Participants also became significantly more aware of when they were daydreaming in the later days of the study.

Carryl Baldwin, a researcher from George Mason University, said electroencephalograms were used to monitor participants' brain activity during the drives. The EEG data was able to show the change in the participant's attention levels, and also indicated that the drivers were less receptive to external stimuli.

"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," said Baldwin. "What we are not sure about yet, is how dangerous it is during driving. We need additional research to figure this out. 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."

The EEG results suggest that drivers may not be as prepared to respond to an audible or visible warning when daydreaming. However, the researchers say additional study would be required to look at differences in drivers' reactions to hazards based on their self-reported attention level.

Researchers said one limitation to the study was that all participants were young and healthy, so the study did not measure whether daydreaming frequency varies with other demographics. The study also points out how the controlled conditions of the simulator may have affected attention levels, and that daydreaming may be less frequent during more challenging driving tasks.

Previous studies on the effect of mind wandering have suggested that it is associated with more dangerous driving behaviors. An Erie Insurance Group analysis of 65,000 fatal crashes from 2010 to 2011 attributed 62 percent of them to mind wandering, compared to only 10 percent caused by drivers who were distracted by secondary tasks such as using a phone.

In 2011, researchers determined that daydreaming did not impede a driver's control of a vehicle, but did cause them to focus on a narrower area of the road ahead. A 2014 study linked mind wandering with more dangerous driving behaviors such as faster speed, shorter following distance, and longer response time to sudden events.