This Illusion Shows How Your Peripheral Vision Is Playing Tricks on You

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Photo: Guido Mieth/Getty Images

Of the five senses, sight seems to be the most trustworthy. It’s the one that’s most helpful in getting us through the day, the one that pushes us the most from I think to I know. Seeing is believing, a picture’s worth a thousand words, etc.

But really, sight is a lot trickier than we give it credit for. Often times, the reality we think we’re seeing is something else altogether — the brain bends visual information to suit its purposes, warping our vision in any number of ways. The sting of rejection, for example, makes us more inclined to perceive a stray glance as eye contact, even when it hasn’t actually landed anywhere near our eyes. New knowledge permanently alters the way we take in a given optical illusion. And, according to a study recently published in the journal Psychological Science, much of what we see in our peripheral vision is just the mind making up things that aren’t really there. A blog post by the Association for Psychological Science explains:

Over a series of experiments, the researchers presented a total of 20 participants with a series of images. The participants focused on the center of the screen — a central image appeared and then a different peripheral image gradually faded in. Participants were supposed to click the mouse as soon as the difference between the central patch and the periphery disappeared and the entire screen appeared to be uniform.

Here’s one example (and you can try out more for yourself here):

The researchers fiddled with different elements of the image across different rounds, altering things like shape or color to see whether some factors were easier to detect in peripheral vision than others. But across the board, the study volunteers continually fell victim to what the authors called the “uniformity illusion”: the belief that what they saw on the periphery matched what they saw at the center of their gaze, even when the two were mismatched.

But the illusion, the researchers argued, wasn’t a trick so much as a shortcut; we don’t take in as much information from our peripheral vision as we do from the center, so the brain makes an educated guess to present a clear picture of the world. “This effect seems to hold for many basic visual features, indicating that this ‘filling in’ is a general, and fundamental, perceptual mechanism,” Marte Otten, a psychologist at the University of Amsterdam, told APS. “Perhaps our brain fills in what we see when the physical stimulus is not rich enough.” Helpful, yes, but also a reminder that just because you see something with your own two eyes doesn’t necessarily mean you should trust that it’s real.

Peripheral Vision Is Your Brain Playing Tricks on You