Much of what we see through our visual perception is often distorted and far from reality. Take this image for instance: This is a powerful optical illusion which can be used to demonstrate that you don't see how things really are. Our visual system is made up of complex processes that try to make sense of what we see. This is the point where optical illusions can create distortions in our vision. In this case, the contrasting colors: green and gray lines cause the lines to appear distorted or curved even when they are actually straight. This illusion is called Muller-Lyer Illusion and it has been studied extensively in psychology and neuroscience.
This viral illusion was uploaded by a Twitter user. One of the comments said, “Because of the peripheral vision, you only have luminance captors with less resolution. Well placed gray square with equivalent luminance to green blend with the lines making you see curves.”
The reason why the gray square looks curved even though it's straight is because of how our eyes and brain work together. Our eyes have parts that see the sides of what we're looking at, called the peripheral vision. These parts are not very good at seeing details like color. They mostly see if things are bright or dark. So, when we look at the green lines next to the gray square, our brain thinks they all kind of blend together. It makes us see the gray square as if it's curved even though it's straight! This is called the Cornsweet trick and a cool scientist found it out in 1970.
