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Cell phone use slows reaction time, study shows


In a controlled study of licensed car drivers, researchers at Miami University found reaction time for braking was 24 percent slower when subjects were using a cell phone than when they weren’t.

"That’s a significantly slower reaction time. At 65 miles per hour, such a delay would increase stopping distance by nearly 10 feet," says William P. Berg, associate professor of physical education, health and sport studies. "This is a considerable delay, especially considering that all the research participants had to do was focus on and react to the simulated brake light. In actual driving, the demand for attention would be far greater, and therefore, so could the delay."

Berg and former graduate students Marcia Irwin and Chris Fitzgerald also tested varying intensities of telephone conversation but found little difference in reaction time.

In a simulated driving task, 16 young adults were each told to move their foot from the accelerator pedal to the brake as quickly as possible when they saw a red light come on. Reaction time was recorded without a phone and under four listening/talking conditions:

  • listening to a weather report on the phone,
  • answering simple questions
  • answering challenging questions and
  • answering questions about beliefs or issues that might elicit an emotional response or about which persons may have strong views.
There was no difference in reaction time between male and female drivers.

The study is reported in the August issue of the journal Perceptual and Motor Skills.

Berg, whose research covers areas of human movement, has previously studied the effect of age-related changes in vision on mobility in older adults and the relationship between muscle strength and mobility in older adults.


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