Can you with certainty say what is real or not? How do you prove that what you see is real?
According to a new study not everything you see is actually real. Many things around you are a visual illusion, scientists say. There is even a simple test you can do to find for yourself how real the illusory experience is.
We almost never contemplate whether our surroundings are real or not. We simply assume that our perception of the world directly and accurately represents the outside world. However, visual illusions of various kinds show us that this isn’t always the case.
As the brain processes incoming information about an external stimulus, we come to learn, it creates a representation of the outside world that can diverge from reality in noticeable ways.
Researchers at the University of Amsterdam suggest that what we see in the periphery, just outside the direct focus of the eye, may sometimes be a visual illusion.
The new findings have been published in Psychological Science, a journal of the Association for Psychological Science.
The findings suggest that even though our peripheral vision is less accurate and detailed than what we see in the center of the visual field, we may not notice a qualitative difference because our visual processing system actually fills in some of what we “see” in the periphery.
“Our findings show that, under the right circumstances, a large part of the periphery may become a visual illusion,” says psychology researcher Marte Otten from the University of Amsterdam, lead author on the new research.
“This effect seems to hold for many basic visual features, indicating that this ‘filling in’ is a general, and fundamental, perceptual mechanism.”
“Perhaps our brain fills in what we see when the physical stimulus is not rich enough,” she explains. “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.”
Researchers came to this conclusion after conducting a series of experiments.
20 participants were asked to look at a number of images. When 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.
The defining characteristic of the central image in different experiment was changed. The image’s shape, orientation, luminance, shade, or motion varied.
The results showed that all of these characteristics were vulnerable to a uniformity illusion – that is, participants incorrectly reported seeing a uniform image when the center and periphery were actually different.
The illusion was less likely to occur when the difference between the center and periphery was large; when the illusion did occur on these trials, it took longer to emerge.
Participants indicated that they felt roughly equally sure about their experience of uniformity when it actually did exist as when it was illusory. This suggests that the illusory experiences are similar to a visual experience based on a physical visual stimulus.
This is an experiment everyone can try and test. “If you look up the illusion on www.uniformillusion.com you can find out just how real the illusory experience feels for you, “Otten said.