Optical Illusions

The circle appears to be colored light blue — but it's actually the same shade of white. This type of illusion first appeared in 1971, when psychologist Dario Varin published one in the book "Chromatic Contrast and Diffusion Phenomena." The reason your eye perceives the circle to be the same color as the lines is relatively unknown.

This is Troxler's fading circle. If you stare the dot for at least 20 seconds, the circle will completely fade away. The circle fades away because of the eye's tendency to prioritize. If you focus on the dot, all other stimuli in your peripheral vision will fade away. Your entire body adapts to stimuli like this. You can test this on your arm very simply: Put a small piece of paper on your arm, and, after a few seconds, if you don't move, you'll stop feeling the paper. Neurons adapt to new things and then move on. So, your eye sees the circle, but is more focused on the dot and unconsciously decides to stop seeing the circle.

This composite of Marilyn Monroe and Albert Einstein is known as a hybrid image. This illusion can do more than just give you a headache. It can also help diagnose vision problems. For example, if you wear glasses, try taking them off and leaning away fom the screen. Einstein might fade away altogether, and you'll only see Monroe. This is because when someone has poor eyesight they lose their ability to see fine details and instead concentrate on the big picture. Einstein's more detailed features are laid on top of a blurry photo of Monroe — so someone with vision problems will focus on the blurrier face of Monroe.