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9/15/2004 12:05:00 AM

Reaction time studies

Studies on people's reaction times have produced some interesting results, including the fact that the more choices you have, the more time it takes you to react to them. While re-examining this phenomenon, a Rice University researcher has begun to access its implications for activities such as driving a car while using a cell phone.

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Several states have laws requiring drivers to use “hands-free” devices when they talk on a cell phone and operate a car. The theory is, a driver will have slower reaction time – and thus be potentially dangerous – holding a phone and operating a car at the same time.

But ongoing research by a Rice University professor suggests those new laws may not be effective. A study co-authored by kinesiologist Bruce Etnyre found that reaction time –

the amount of time it takes to think about a task or choice and respond – is longer when a person is presented with multiple tasks that divide attention.

While prior studies have tended to examine a single reaction time, Etnyre and Priscilla MacRae of Pepperdine University decided to utilize three different types of tests. In the first two, they examined reaction times to a single light and then 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.

The researchers found differences in reaction times between the visual and sound tests: subjects responded much more quickly to the single auditory signal than to the single visual signal. In the tests which required subjects to split their attention among four different lights, reaction times became even slower, confirming prior findings which indicated 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 device should be used by someone while operating a car. When his subjects had to split their attention between four different lights, their reaction time was noticeably diminished. Similarly, drivers using either type of cell phone are necessarily splitting their attention between their phone conversation and their driving, and that, according to Etnyre, is what will slow their 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.”

Etnyre, who presented their findings at the North American Society for Psychology of Sports and Physical Activity in Vancouver, is continuing to study reaction time in driving simulations. Most recently, he has been researching the motor control of female athletes who have undergone knee surgery, specifically on their anterior cruciate ligaments.

A graduate of Valparaiso University, where he majored in kinesiology and English, Etnyre earned a master's degree from Purdue University in kinesiology and English and a second master's degree in physical therapy at Texas Women's University. He received his doctorate in motor control and biomechanics from the University of Texas in Austin and is a licensed physical therapist.

A member of the Society of Neuroscience and the American College of Sports Medicine, Etnyre joined Rice's faculty in 1984 and currently is a professor and chair of the kinesiology department.

To learn more about this research, contact Etnyre at etnyre@rice.edu , or Ellen Chang in the Office of News and Media Relations at ellenc@rice.edu .