Nothing is as it seems, especially if it’s in your peripheral vision.

Our peripheral vision, the part of sight outside the center and focus of our gaze, might often be an optical illusion, according to a new study by the University of Amsterdam and published in Psychological Science. In an attempt to account for what our periphery cannot see, the researchers believe our brain essentially tries to “fill in” the blanks to give a full picture.

“Perhaps our brain fills in what we see when the physical stimulus is not rich enough,” lead author Marte Otten, from the University of Amsterdam, explained in a statement. “The brain represents peripheral vision with less detail, and these representations degrade faster than central vision. Therefore, we expected that peripheral vision should be very susceptible to illusory visual experiences, for many stimuli and large parts of the visual field.”

Their study gathered a small sample of 20 participants and presented them with a series of moving patterned images, varying in their shape, orientation, luminance, shade, and motion. On the periphery of the picture, a different image gradually faded in. You can see an example of the images in the video below. Just stare at the flashing yellow dot and notice how the shapes all appear uniform.

They asked the participants to stare at the center of the screen and click a computer mouse as soon as the difference between the central image and the periphery image disappeared, making the overall image uniform.

The results showed they were unanimously very poor at the task, often saying they saw a uniform image when the center and periphery were actually different.

“Our findings show that, under the right circumstances, a large part of the periphery may become a visual illusion," Otten added. "This effect seems to hold for many basic visual features, indicating that this ‘filling in’ is a general, and fundamental, perceptual mechanism."

“The fun thing about this illusion is that you can to test this out for yourself,” Otten said. “If you look up the illusion on www.uniformillusion.com, you can find out just how real the illusory experience feels for you.”