You can drive while you talk, and talk while you drive, but you will perform worse at both.
It's been proved that having a conversation, on the phone or with a passenger, while driving can make you a worse driver.
But now researchers from the University of Illinois have found that the opposite is also true: Driving can make you a worse listener.
Someone who is driving has a harder time understanding conversations and analyzing language, said Gary Dell, a psychology professor and co-author of the study published in the Psychonomic Bulletin & Review.
Previous research on the topic had failed to link driving to impaired speech, something that surprised Dell.
Using and understanding language require attention, which is lessened by the need to focus on driving, he said.
Illinois researchers used driving simulators to test their theory.
In the experiment, a driver would try to remember conversations with a passenger in the car or with a person on the phone, using a hands-free headset.
About 100 people, from teenagers to adults older than 65, participated in the study.
The driver would be asked to listen to four stories, half while sitting in the car but not operating it, and the other half while navigating through simulated busy city traffic.
Then the driver was asked to retell the stories.
Their ability to remember details and repeat what they heard improved if they were not driving when they heard the story.
Drivers remembered 20 percent less of the stories that they heard when they were driving compared to when they were sitting still and listening, Dell said.
Participants' listening comprehension declined further when the driver was moving through intersections or other more demanding driving skills, Dell said in a statement about the research.
"With modern technology, we're talking more and more while we are doing other things, but we may be understanding one another less and less."