By Peter M. Vishton, Ph.D., William & Mary

Edited by Kate Findley, The Great Courses Daily

Dr. Vishton offers a neurological perspective on why driving while using a cellphone—yes, even a hands-free device—is so dangerous. But what about talking to fellow passengers while driving?

Driving and Multitasking

Perhaps the most publicized real world application of research on multitasking has come in the domain of driving while using a cell phone. Driving while texting or talking on a phone carries an even higher risk than driving while legally intoxicated. 

When you’re reading and typing text messages on a phone, you have to look away from the road, at least for a few seconds at a time. If something happens in front of your car during those few seconds, there’s no way you can react in time. Even when you talk on a handheld cell phone, you usually have to look down to dial the number or select the contact and hit send.

Phone manufacturers and car companies have addressed this problem: They’ve created hands-free cell phone usage. The idea here makes total sense. You create a phone that can respond to your voice commands—statements like “call Mom” prompt the phone to make a call to that person. 

When an incoming call arrives, the phone states who the caller is and you can accept or decline that call. You can even have a cell phone read your text messages to you and, if you choose, dictate a reply to be sent via its text message system. 

Problem solved, right? Unfortunately, no.

While a hands-free system can enable you to keep your eyes on the road the whole time, several studies have found that the increased accident rate stays almost as high with hands-free cell phone usage as it is with handheld cell phone usage. The problem can be summed up in one word: multitasking.

When Bottlenecks Become Dangerous

Experiments on multitasking apply very specifically to this situation, in at least two important ways. First, when it comes to processing sensory information and making a discrete decision about it, the human brain is limited to one decision at a time. 

No matter how skilled you are at the other components of performing the task, the decision part remains a single-task bottleneck. When you’re pondering the statements of someone on the other end of a phone or text exchange, you’re making a lot of decisions: “Should I respond now or keep listening? What should I say?”

Every time you’re making one of those decisions, you’re not able to make visuomotor action decisions about driving the car: “Should I hit the brakes? Should I change lanes?” Those decisions have to wait until the bottleneck is freed up. 

We get very good at alternating between two or more tasks, but the switching always introduces a slight delay. At 60 or 70 miles per hour, that delay can translate into the difference between avoiding a collision and having an accident.

When we make short-term, immediate decisions, we tend to do so with our gut rather than after careful consideration. You won’t be mentally reviewing the studies of multitasking when the phone is ringing. Your unconscious mind will just be thinking about the immediate reward of learning who’s on the phone and why.

The tip that emerges from this is simple. When you get into the car, before you turn the engine on, turn the phone, or at least the ringer, off. If there’s some pressing call or message that you’re waiting for, then ideally, pull off the road safely and park in a parking lot somewhere.

Then turn the phone back on to check it. It might seem annoying, at least at first, to stop every half hour or hour for this purpose, but that annoyance is well worth the safety of yourself, your passengers, and the other people on the road.

Passenger Distractions

When considering the dangers of multitasking while driving, you may wonder if talking to an actual person sitting in the car next to you is also a problem. There have been a lot of studies showing the problem for cell phones, but very few have addressed non-cell phone distractions.

The National Traffic Safety Board recently published results from an ongoing study in which dashboard cameras were installed into the cars of thousands of volunteers. The researchers looked at about 1,700 videos taken in the moments leading up to a reported crash by teenage drivers. 

In 60 percent of the cases in which an accident happened, the driver was distracted. In 15 percent of these cases, it wasn’t the cell phone that was the distraction, but rather one or more of the passengers in the car.

It’s reasonable to presume that this finding could be applied to adults as well. The information processing bottlenecks associated with multitasking aren’t something you just outgrow. 

“As someone who takes long trips with my family in the car, the thought of not talking with them while I drive sounds pretty unpleasant, but the data here suggests that I should minimize that,” Dr. Vishton said. “If I’m embroiled in a conversation about something … then I’m multitasking. And when I’m multitasking, I’m putting everyone in danger.”

Now, you may listen to music or audiobooks while driving—this is not considered multitasking. As long as you’re just listening, there should be no need for task-switching. While tuning the radio and selecting a station are decision-making processes, just listening without making decisions should be fine.

This article was edited by Kate Findley, Writer for The Great Courses Daily.

Dr. Peter M. Vishton is Associate Professor of Psychology at William & Mary. He earned his Ph.D. in Psychology and Cognitive Science from Cornell University. Before joining the faculty of William & Mary, he taught at Northwestern University and served as the program director for developmental and learning sciences at the National Science Foundation.