Depth Perception in Driving: Alcohol Intoxication, Eye Movement Changes, and the Disruption of Motion Parallax

Motion parallax, the ability to recover depth from retinal motion, is a crucial part of the visual information needed for driving. Recent work indicates that the perception of depth from motion parallax relies on the slow eye movement system. It is well known that that alcohol intoxication reduces the gain of this slow eye movement system, the basis for the "horizontal gaze nystagmus" field sobriety test. The current study shows that alcohol intoxication also impairs the perception of depth from motion parallax due to its influence on the slow eye movement system. Observer thresholds in both active and passive motion parallax tasks are significantly increased by acute alcohol intoxication. Perhaps such a failure of motion parallax plays a role when intoxicated drivers must make quick judgements with what could be inaccurate or missing perceptual information about the location of obstacles around them.