click here to see the optical illusion

Directions for the Optical Illusion


Focus your eyes on the x in the middle of the circle made up of magenta circles. You will notice that as the pattern of movement continues around the circle, one magenta circle briefly disappears then reappears. You should then notice a bright green color whenever the magenta circle disappears. Upon fixating your eyes on the x longer, you should see a rotating green spot. Eventually the magenta circles will disappear altogether if your eyes are steady enough (the magenta circles reappear upon making any eye movements).

Using the buttons on the side of the optical illusion, you can also change the color, saturation, and speed of the optical illusion. This will allow you to see what happens when other colors are viewed.

Eye Physiology Behind the Optical Illusion



The process of being able to see an image through the eye begins with light from the image passing through the cornea. From the cornea, the light then passes through the choroid layer which prevents light scattering. It then passes to the retina which contains photoreceptor cells called rods and cones. After the retina, signals pass from the photoreceptor cells to bipolar neurons and then into ganglion cells. The signals then leave the retina and travel toward the brain through the optic nerve. They then cross at the optic chiasma, pass through the optic tracts to the thalamus and the signals end at the visual cortex of the occipital lobe where they are interpreted as an image.

The photoreceptor cells, rods and cones, which are found in the retina, are responsible for the change of color seen in the above featured optical illusion. Cones allow us to see color, while rods allow us to see various shades of gray. Rods are most frequently found towards the edges of the retina and allow for dim light vision and peripheral vision. Cones on the other hand allow for detailed color vision and are found in highest concentration in the center of the retina. There are three different types of cones, blue, green, and red. The type of cone being used in seeing an image dictates what proteins will be produced, and in turn, the proteins decide what color will be seen. Therefore, the color being seen is due to a release of proteins. When the eye is exposed to the same color for a longer period of time than normal, proteins for that color will overproduce and flood the eye. This is the concept that is seen in this particular optical image. Due to the fact that the eye is exposed to the magenta circles for a longer period of time, the eye overproduces those color proteins, tiring out the cones for that color, causing them to stop responding. However, then the surrounding cones that are not being excited by the magenta color are still fresh and send out a strong signal. The signal is then interpreted by the brain as seeing the opposite primary color, which is green. This is why the magenta circles eventually appear to be green instead.