— Amid the epidemic of texting and driving, the risk of simple calls behind the wheel has taken a backseat. (Kids, that's where your smartphone facilitates a real-time conversation with someone. Crazy, right?) But such interactions can still pose a safety threat, and a new study by the University of Iowa explores why.
The study, published in the journal Pyschonomic Bulletin and Review, found users' ability to focus on new objects notably slow during active conversations. Researchers tracked users' eye movements between objects that appeared on a screen. When users had to answer true-and-false questions at the same time, they took about twice as long to focus on the new objects.
The implications for driving are clear: Conversations behind the wheel slow your ability to perceive conditions around the car. Researchers found the average delay about 0.04 of a second, with new-object recognition taking about 0.1 second total during such conversations. But UI psychology professor Shaun Vecera, one of the study's authors, warned in a statement that such a delay can have "a snowball effect" as your brain takes more time to disengage from one task and engage with another.
Drivers should be cautious while talking on the phone because "it slows your attention down, and we're just not aware of it because it happens so fast," Vecera said. He also applied the findings to conversations with a passenger, though it stands to reason that a passenger would have the context to pipe down if you were, say, changing lanes on a busy interstate. Someone on the phone would not. (Asked if researchers tested for different conversational conditions, Vecera did not respond.)
Still, this might give you a safety-related excuse when your spouse complains you're a terrible listener behind the wheel. If your spouse says you're a terrible listener outside the car, well, this study can't help that.