Multi-taskers, it is time to choose: either you can drive well or conduct a meaningful conversation, but not do both at the same time. A growing body of research has shown that talking on a cell phone impairs a person’s ability to drive; now Beckman Institute researchers who pioneered distracted driving studies have shown that driving impairs our ability to comprehend and produce language.

Their report, titled Driving impairs talking, appeared in the Psychonomic Bulletin and Review. Authors of the study are Ensar Becic, Gary Dell, Kathryn Bock, Susan Garnsey, and Arthur Kramer of Beckman and the University of Illinois and former Beckman researcher Tate Kubose of Exponent Engineering and Scientific Consulting.

As with past studies of distracted driving done by these researchers, this study was conducted using the driving simulator at Illinois’s Beckman Institute. The experimental setup consisted of a stationary Saturn automobile and three display screens featuring simulated roadways and intersections. The experiment’s parameters made both driving and language production priorities for the test subjects, who consisted of 96 drivers and an equal number of conversation partners.

The results showed, as the authors write, that when it comes to “whether driving an automobile interferes with the ability to process and remember language” the answer is “unequivocally affirmative.”

The experiment required test subjects to listen to a story through earphones and then accurately retell it, in 30 seconds or less, to their partners. That task ensured meaningful language production for the test subjects while the driving task challenged drivers to negotiate an urban roadway environment, obey speed limits, and safely cross busy intersections.

“Driving negatively impacts story retelling as well as the process of comprehending and encoding stories into long-term memory,” they wrote. “In summary, consistency in driving performance while dealing with speech (less driving variability) came at the expense of accuracy in story retelling. When doing the speech task only, drivers and nondrivers were equally good at retelling. When the car was moving, however, drivers displayed a large decline in speech-task performance.”

The stories used in the study were generally three to four sentences long with specific information the subjects were expected to remember and accurately convey to their partners. Both drivers and non-drivers listened to a story through headphones and then retold them to their partner; then the roles were reversed with the partner performing the same task. There were three critical task blocks consisting of two single-task blocks (a driving-only and a speech-only block) and one dual-task block (driving while conversing).

By asking participants to convey the stories accurately, the experiment ensured the subjects used novel sentences and maintained a certain level of engagement. Researchers measured the accuracy of the speech production as well as the memories of the subjects.

“Driving affects both of those for the worse,” Dell said. “It makes you tell the story less accurately and you leave more stuff out. It also makes you worse at remembering the stories that are told to you by your conversation partner.”  

Dell said that, unlike previous studies, this experiment featured the difficult task of re-telling a story accurately while driving in a challenging environment.

“We made the language task more interesting and realistic,” Dell said. “The effects of driving on talking in this study were stronger. They were larger than what anybody would have expected because intuitively we think driving as being affected by speech, not the other way around.”

By focusing on how language is affected by driving, the research has given new insight into how difficult it can be to perform two tasks at the same time, even tasks that are as familiar to most people as driving and talking.

“If the conversation is really important, they are probably going to focus on the conversation and then their driving will suffer,” Dell said. “If the driving is really important, if you are really careful about your driving, the conversation is going to suffer.

“These things – even though we practice them a lot and are very skilled at doing them – are hard things to do and when you put them together in a dual task, they suffer.”