Study: Peripheral vision vulnerable to uniformity illusion

New research suggests human vision is especially vulnerable to illusion at the margins. Photo by UPI/Jim Ruymen. | License Photo

AMSTERDAM, Netherlands, Dec. 8 (UPI) — Many studies have revealed the fragility of human perception. Put simply, humans see things that aren’t there for a variety of reasons.

But some portions of a person’s field of vision are more vulnerable than others. New research proves peripheral vision is especially susceptible to illusion.

Because human vision is subject to physiological limits and peripheral vision is less detailed, researchers at the University of Amsterdam hypothesized the brain’s attempt to fill-in-the-blanks would make the outskirts of human vision more easily fooled by what’s known as the uniformity illusion. Experiments proved the hypothesis correct.

Scientists detailed their discovery in the journal Psychological Science.

“Our findings show that, under the right circumstances, a large part of the periphery may become a visual illusion,” study author Marte Otten, a psychology researcher at the University of Amsterdam, said in a new release. “This effect seems to hold for many basic visual features, indicating that this ‘filling in’ is a general, and fundamental, perceptual mechanism.”

To test their theory, Otten and her colleagues presented study participants with a vision test. Participants were asked to focus on the center of a screen featuring a central image. Images varied in shape, color, motion and brightness. On the outskirts of the screen a different image faded in. Participants were told to click a computer mouse as soon as the screen — the images at the center and on the outskirts — became uniform.

The majority of participants failed the test, clicking the mouse when the central and peripheral images had not become one and the same. When the distance between the central and peripheral images was greater, the participants were less likely to be tricked by their eyes.

Surveys showed participants were equally confident of what they saw and experienced whether they had witnessed an illusion or not. The finding suggests illusions have the same sensory effects as a physical visual stimulus.

“The most surprising is that we found a new class of visual illusions with such a wide breadth, affecting many different types of stimuli and large parts of the visual field,” Otten said. “We hope to use this illusion as a tool to uncover why peripheral vision seems so rich and detailed, and more generally, to understand how the brain creates our visual perceptual experiences.”

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