Alcohol affects the human body in many different ways, none of which are helpful when it comes to safely operating a motor vehicle. However, one impairment people grossly underestimate is the effect alcohol has on an individual’s ability to see clearly. In fact, researchers in Canada recently found that our vision can be impaired by up to 30 percent—and that is before reaching the legal limit.
Published in the journal Perception, the research was conducted by Kevin Johnston and Brian Timney, from the Schulich School of Medicine & Dentistry and Western University’s Social Science department in Ontario, Canada. The men used a classic optical illusion called the Hermann Grid to test their subjects.
When describing how the Hermann Grid works, Johnston said “The Hermann Grid is basically a grid of black squares on a white background. You see ghost-like dark sports at the intersections of the grid, but they are not actually there. It’s the way our visual system processes contrast or brightness differences that creates the illusion.”
In conducting this study, the researchers had participants drink either nonalcoholic drinks or enough to keep them just under the legal limit of 0.08 percent. After drinking, the people were presented with the Hermann Grid. It was established that those who drank the alcohol saw a 30 percent reduction in the contrast of the spots on the grid.
The researchers feel this is extremely important information, especially for people driving under the influence at night time when it’s already more difficult to see. If vision was reduced by 30 percent in someone who was legally allowed to get behind the wheel of a car, can you imagine what it’s like for someone who is driving at twice the legal limit?
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