Effects of Visual Challenges on Steering Ability: Testing the Selective Degradation Hypothesis

Most young drivers are comfortable driving at night despite the increased danger. The selective degradation hypothesis predicts that drivers' overconfidence at night is a consequence of their ability to steer being preserved even though their ability to recognize details is impaired. To test this hypothesis, ten participants drove a curvy simulated roadway with varying levels of luminance, blur, and visual field size. Steering performance, but not visual acuity, was degraded when the visual field was reduced. Acuity, but not steering performance, was severely degraded by extreme blur and extremely low luminance. These findings support the selective degradation hypothesis, suggest that separate neural mechanisms support visual recognition and visual guidance skills, and emphasize the problems that occur when unexpected low contrast objects are present in the roadway environment at night.