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Eye Speed: How You See It (and Why You Don’t)

Posted on 2014/05/30 at 2:59 pm by LASIK MD

Predicting the speed of objects is an essential part of everyday life. From crossing the street to pouring a cup of milk, we need the ability to estimate how fast something is traveling in order to make it across busy intersections and keep floors spill-free. But how does eye speed work? Do we really see what’s coming, or just take our best guess?

Why Did the Researchers Cross the Road?

In the case of those from the Royal Holloway University of London, it was to determine if humans could accurately predict the speed of oncoming traffic and judge when it was safe to cross the road. The team found that one of the best visual cues for speed was what’s known as “looming.” This is the expansion rate of an object’s visual image as it approaches; the faster it looms, the more quickly it approaches. In addition, the Royal Holloway researchers found that we all have a natural looming threshold above which our perception of speed becomes distorted. Part of the problem is the correlation between speed and distance. A car driving at 25 miles per hour looms significantly when it’s “too close” to make crossing safe, keeping us firmly on the curb. Cars traveling 50 miles per hour, meanwhile, can be twice as far away but still pose the same risk. The problem? At greater distance, they don’t loom nearly as much. So, part of our eye speed mechanism relies on the actual position of objects and how quickly their image seems to approach.

Batter Up!

What about smaller, faster objects, like baseballs? Hitting guides love to talk about “seeing the ball,” but is it really possible to keep your eye on a tiny white sphere moving close to 100 miles per hour? According to the Los Angeles Times, reporting on a recent UC Berkeley study, no. Instead of tracking the actual position of a baseball as it comes hurtling toward us, we’re able to “predict” the position of the ball using a portion of the brain’s middle temporal complex. To compensate for the delay in signals moving from the eye to the brain, the temporal complex “starts pushing the object forward to compensate,” allowing hitters to anticipate where the ball will be when they swing. This also works in real life for slower-moving objects, like a stream of milk. If we stopped pouring when the glass was actually full, signal delays would cause gallons of spilled milk each year. Instead, our brains warn us when the glass is almost full by making it seem entirely full; as a result, we stop just in time. If you want to see an example of this predictive motion, check out the Flash-Drag illusion.

Of course, looming and prediction aren’t the only components in accurate eye speed. Excellent visual acuity also plays a role in how well you’re able to see an object coming—if you’re not able to focus on faraway or close-up objects, it’s much more difficult for your brain to judge speed. Glasses may also hamper your ability to predict speed if what you’re trying to see moves behind bulky frames or lens glare impairs your view. If you’re looking to improve your eye speed—and visual acuity—one option is laser vision correction. This safe, quick-healing procedure painlessly reshapes your eyes to enhance visual acuity, giving a better view of the world around you and helping you see what’s coming.

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