Optical illusions are images that fool the brain. The images give the viewer a certain impression at first sight, but if they are observed more carefully, they will show a different visual representation.
An example of an optical illusion is a three dimensional drawing of a cube that looks like a cube as well as a half-cube. The picture shows an image of a cube with alternating tiles of black and white tiles in the background. At first, it looks like an ordinary cube hanging in the air, but when the viewer focuses on the corner that is pointing outwards, the cube will look like a half cube with only three sides.
Another popular optical illusion is the tribar, which is the image of a supposedly three-dimensional triangular structure that looks normal at first sight. On close examination, it becomes obvious that it is an impossible shape that is not three-dimensional at all. One other famous example of an optical illusion is the “duck and rabbit” picture. The image can be a rabbit facing right, with its ears pointing backwards to the left, or it can be a duck facing left with its beak in the same direction.
Optical illusions fascinate a lot of people. When they started gaining popularity in the 1980s, they were known as “magic eye” pictures, and they were often sold as large posters. While some people thought that only intelligent people could see the illusions, others thought that they needed eye glasses to do so. Actually, it is just a matter of using the right technique to look at the pictures, which is to focus behind the picture.
Optical illusions succeed in fooling people because they provide more than one visual representation in a single picture. When a person looks at a certain image, the brain has certain visual expectations, and it will naturally focus on familiar images that it has experienced before. When the brain is focused on a visual representation, it may not be able to adapt to the presence of another illusion within the same picture. However, if a person is told to focus on something else other than the familiar image, his or her brain will be able to make conscious adjustments and spot the illusion.
It is very easy for people to make optical illusions of their own. One of the simpler optical illusions is the “black intersecting lines with grey spots”. Just draw five horizontal lines and 5 vertical lines, and then, focus on the spots where the lines intersect. After focusing for a while, it will look as if there are grey spots at the points of intersection. The grey spots will also show if white lines are placed over a black background. There are also color illusion images and illusion structures that can be crafted with paper and other materials.
Here is a list of websites that contains images of optical illusions as well as instructions on how to make optical illusions.