How many horses do you see?

Optical Illusions (also called visual illusions) are visually perceived objects and images that differ from reality. The information that is gathered from the image is processed in the brain to give a perception that is in fact, inaccurate according to the physical measurement of the stimulus source.

In the case above, colour has been very cleverly used to create an optical illusion of more horses than there actually is within the image - when in fact it is the background which the use of the same colour(s) (brown and white) very cleverly places an image of several horses in the foreground of the image (within the viewers mind.)

It is easy to depict which horses are actually being portrayed within the image, for example, the black/brown colour of the horses tail belonging to the horse in the very foreground of the image is clearly not an illusion as the tail does not fit in with the much paler brown and white colours of the intended background.

In the grid illusion above, ghostlike grey and black circles appear when this image is viewed - then when you look directly at an intersection they disappear. Shape, position, colour, and 3D contrast converge to product the illusion of the dots at the intersections.

In the image above, the black dots appear to form and vanish at the intersections of the gray horizontal and vertical lines. If you focus your attention on a single white dot, both grey and black dots appear, and if you scan your eye across the image more black dots seem to appear. The effect is reduced when you position your head to an angle, and if the eye is moved very close to or far away from the image the black dots do not appear at all.