Hang Up and Drive

Several states have laws requiring drivers to use “hands-free” devices when they talk on a cell phone while driving a car. The theory is that a driver has a slower reaction time while holding a phone and operating a car at the same time, which could cause potential dangers. But ongoing research by a Rice University professor suggests those new laws may not be effective.

Using three types of reaction tests, Bruce Etnyre, professor and chair of kinesiology at Rice, and Priscilla MacRae of Pepperdine University found that reaction time is longer when a person is presented with multiple tasks that divide attention. In the first test, they examined reaction times to a single light and, in the second, to a single auditory signal. In the third test, the subjects were given a choice of four buttons with lights. When one of the four lights came on, their reaction time was measured by how long it took them to press the corresponding button.
Subjects responded much more quickly to the single auditory signal than to the single visual signal, but in the tests that required subjects to split their attention among four different lights, reaction times were slowest of all, confirming prior findings indicating that multiple tasks lengthen a person’s response time. Gender differences also were confirmed, with men performing better on all three reaction tests than women.

In the debate over hands-free versus hand-held cell phones, Etnyre’s tests suggest that neither should be used by someone driving a car because both split drivers’ attention between their phone conversation and their driving, slowing reaction time.

“Whether the driver’s hands are on the wheel or free doesn’t make a difference in how fast they can react to something on the road,” Etnyre says. “It’s not necessarily a matter of physically controlling the car while holding the phone. It’s the fact that they have to switch their attention between driving the car and listening and talking with someone.”

—Pam Sheridan