What are some major optical illusions

Optical illusions - that's why your eyes can be tricked

With an optical illusion, you perceive what you see to be different from what it actually is. However, this has nothing to do with your eyes directly, but with the processing of what you see in the brain.


Do you believe your eyes An optical illusion can often make you doubt it. You then see things that are not there or that a second person may perceive completely differently. But don't worry: such visual illusions do not indicate a problem with your eyes or your mental health. They are completely normal and trick everyone from time to time.

What is an optical illusion?

Optical illusions and illusions arise when your brain perceives something through the visual impression that does not coincide with the objectively measurable reality. They can take many forms: from crooked lines that are actually straight to color illusions and images in which different people see different things. Optical illusions are not uncommon in everyday life, but they are also exhibited in museums or become internet phenomena. The ways in which the human eye can be irritated is fascinating. Convince yourself of it!

Optical illusions with colors

How we perceive a color also depends on which other colors surround it and what kind of light conditions are available. For example, it can happen that you suddenly perceive what is actually a gray point as reddish when it is depicted on a green surface. Perhaps you still remember the black and blue dress that was circulating on social networks for a while? Because of the yellowish artificial light in which it was photographed, many people saw it as a white and gold dress.

Another optical color illusion is created by the so-called Troxler effect. If you concentrate longer on a point in the middle of an image, the colors at the edge begin to fade until they can no longer be seen at all: Permanent, tiny eye movements (microsaccades) ensure that the light on the retina is permanently shifted and we can see something permanently. However, if the visual stimulus remains the same over a longer period of time, the brain gradually fades out the information. This effect also ensures that you do not see your own nose or the edges of your glasses permanently, although they are always in the field of vision.

Size deception

With this optical illusion, objects of the same size appear to be of different sizes. Lines of the same length can also appear of different lengths. The effect depends on the arrangement in a perspective space.

Illusion of movement

Surely you also know pictures that appear to move when viewed - they actually stand still. The areas that move are usually the ones that the eye is not in focus at the moment. With this visual illusion, it seems as if circles suddenly rotate in an image or the entire background moves.

Perspective interaction

With a perspective interaction, an object appears in an image once in the foreground and then in the background - and vice versa. You can usually jump back and forth between the two perspectives at will. This is how a three-dimensional effectalthough the picture is two-dimensional.

Visual aftermath

For a visual after-effect, an object is first viewed for a certain period of time - usually half a minute. If you then turn your gaze to a bright surface, you will see an image of the object there in its complementary colors. This optical illusion arises because the photoreceptors of the eyes tire for the actual color of the object with prolonged concentration. The phenomenon is also used to test the retinal correspondence, which plays a role in binocular vision.

Phantom image as an optical illusion

A phantom image is a visual illusion because it is interpret ambiguously leaves. For example, it is known to depict two faces looking at each other. The gap between the two figures forms a chalice. Some people see the faces, others see the cup first. But if you know, you can also concentrate on the other form and thus mostly recognize it.

Ambiguous representations

In an ambiguous representation are in a single image several image variants hidden. For example, if you see a rabbit the first time you look, it turns into a duck when you look at it for a long time. Some only recognize this effect if they are made aware of it. Once you've seen both variations, it becomes impossible to focus on just one variation.

Impossible objects

With the optical illusion with impossible objects, an object is depicted that can only exist in two dimensions. At first glance, the depicted object appears quite ordinary - on closer inspection and the three-dimensional conception of the object, it becomes clear that this cannot exist. An example of this is the Penrose triangle, also known as the Tribar.

This is how optical illusions can be explained

Optical illusions are not uncommon. The process of seeing is a Interaction between the eye and the brain. A healthy eye (even with glasses) correctly perceives the environment and passes the information on to the brain. The brain doesn't just rely on the sensory impression alone - it also resembles it with empirical values. So it tries to give a meaningful meaning to all things that the eye registers. The elongated brown object with green objects at the top becomes a tree. And so the brain also interprets an impossible object as a possible one.

Because the brain has to make a decision within a fraction of a second, only one variant is initially recognizable in an ambiguous representation. At the same time, the brain produces misinterpretations and perceptions of things that are not there at all - it completes them from memory. Often you only become aware of the optical illusion if you look longer and absorb more information.

Optical illusions do not mean that something is wrong with your perception, but even demonstrate how our visual process takes place. So the next time you stumble across a visual illusion, you don't need to worry, you can enjoy its fascinating effect with peace of mind.