Peripheral vision of humans is weak. We can hardly distinguish details, colors, and shapes by using this type of sight. The reason for this is the density of receptor and ganglion cells in the retina. They are much denser at the center than at the edges. Basically, we use our peripheral view for recognition of well-known structures and forms with no need to focus on the foveal line of sight.
Recently, scientists from the University of Amsterdam conducted a research. The team investigated a visual illusion that shows that detailed peripheral visual experience is partially based on a reconstruction of reality. Several volunteers were shown series of images. Those images appeared in the center, which was then gradually joined by a separate picture fading in from the edge. Volunteers should focus on the center and click the mouse as soon as the difference between the central patch and the periphery disappeared. All volunteers poorly did this task as they clicked the images that actually were deferent. Psychology researcher Marte Otten said that this result indicates that perhaps our brain fills in what we see when the physical stimulus is not rich enough.
The human brain, although highly sophisticated, processes information in a very basic way. As we move our eyes from left to right, we pick up visual cues directly. However, in our peripheral vision that our brain then processes piece by piece and not continuously. Our brains process high-contrast elements, like black on white, faster than low-contrast ones, like black on gray, that lapse in mental read time is ultimately what causes the optical illusion.
Any optical illusion that our brains perceive as moving but, in reality, is still is known as peripheral drift illusion. If you would like to test your peripheral vision, look up the illusion on Uniformity Illusion. It is wonderful to experience how brain and eyes work together and yet how much is easy to trick our brain into perceiving something one way when in reality it’s another.