By Luciana Gravotta

The driving simulator used in the experiment

Conversation is more than a simple distraction: It can activate parts of your brain involved in seeing and doing and interfere with vision and movement. These areas are highly engaged when you’re telling a coworker which drawer to open to find the files (an action), but not when he asks you for the square root of 16 (an abstract concept).

A new study in the Journal of Experimental Psychology used a driving simulator to understand how our performance on the road is affected by the way our brain processes language. Here are some of the surprising findings.

It's Not How You Say It, It's What You Say

When subjects talked about movement or appearances, they seemed to be more distracted than they would be by abstract topics and ended up with more distance (on average) between their car and the car ahead. Why? Researchers think this may happen because there is an obvious, almost automatic cue to trigger braking—seeing the brake lights in front of you—but no equivalent cue for speeding up. Over time, as your spatial attention is repeatedly directed elsewhere, you end up further and further away from the car ahead. The conversational distraction means you are slower to hit the brakes, but the extra space between cars may mitigate the danger. 

When people discussed abstract ideas, however, the movement and vision areas of the brain were not engaged by language processing. With those areas freed up for driving, subjects monitored distance as they usually did, keeping a normal (shorter) distance between their car and the next one. The distraction of conversation still slowed reaction time, but—unlike in the first condition—there was no longer extra space between cars.

Drive in Silence? Not Exactly.

While it may seem reasonable to think that you should stay away from philosophical discussions and focus on conversation about opening jars or the colors of the rainbow, the extra space cushion you gain with more concrete talk is the result of a very distracted brain—a bad condition for a driver any way you slice it. Maintaining proper distance is only one small part of safe driving, and it won't help with the many other on-the-road dangers that require your full attention.

The study suggests that distraction is not a monolithic phenomenon, and that understanding how particular types of distraction affect performance and safety may be worthy of ongoing investigation. Furthermore, interference with visual attention and control is caused not just by speaking but also by listening and comprehending, a finding that could indicate problems with in-car use of everything from email to language tapes and GPS devices.

“Language can be a powerful interface tool for applications like these, but it can also increase cognitive load on the user and impair performance,” warns Benjamin Bergen, a cognitive scientist at the University of California San Diego and the lead author of the study.

Still, drivers shouldn't feel the need to demand absolute silence just yet. Some studies suggest that passengers, unlike the person on the phone or the the voice on the radio, do not impair drivers with their banter. Why? It may be because they’re sharing the same road experience as the driver: They know when to keep mum or even give warning of potentially dangerous situations. Bergen’s next study will test exactly this: Does a blindfolded traveling companion make for a more dangerous one?


Luciana Gravotta is a freelance science writer. She is currently an editorial intern at Psychology Today.

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