In one study, drivers were given simple concentration exercises to perform while driving. None required drivers to remove their eyes from the road. However, performing the exercises significantly diminished the drivers' ability to drive. Specific changes in driving behavior included tunnel vision, decreased road scanning, and decreased use of rearview mirrors. Drivers also reduced their speed when performing the exercises.

The bottom line? Drivers need to keep their eyes on the road -- and their minds on driving.

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