An optical illusion, which is also referred to as a visual illusion, is characterized by images that are visually perceived that are different from reality. The main purpose of such illusion is to force the eye to gather information wrongly which is then processed in the brain which results in a perception that differs from the reality.
There are 3 main kinds of optical illusions. The first one is called literal optical illusion, which can create a picture that is different from the object used to make them. The second type is called physiological illusions which can affect the brain and its perception of certain images by stimulating the brain and the eyes excessively. This type of illusion is based on the movement of the object, its size, its position, its color and its brightness. The third type is called cognitive illusion, which is caused by unconscious inferences.
This type of optical illusion includes afterimages, which can be seen after the eye is faced with bright lights or by exposing the eye excessively to alternating patterns. The theory that this type of illusion is based upon is that the stimulation that happens in the neural path in the early phases of processing as well as the repetitive activity or the intense activity can cause a physiological imbalance that results in the alteration of the brain’s perception of the image. Thus, causing the illusion and causing the brain to see something differently or something that is not really there. The Mach Bands and the Hermann Grid illusions are the 2 illusions that can be explained by using a biological and a scientific approach.
Cognitive illusions are quite tricky. It all depends on how we perceive the image and what do we focus on. In this type of illusion, a picture can show two things, when you first see it, you will see one thing and if you focus more, you can see that there is another. This kind of illusions is divided into 4 different illusions. There are distorting illusions, fictional illusion, paradox illusions and ambiguous illusions.
Distorting illusions: They are also called geometrical illusion. They are characterized by the distortion of the curvature, position, size or length of the object. Some popular optical illusions that fall under this category is the famous Ponzo Illusion, the Muller Lyer illusion and the Café Wall Illusion.
Fiction illusions: It is when the brain perceives a certain figure or an image, despite the fact that this figure is not in the stimulus.
Paradox Illusions: It is a type of illusions that is generated by certain objects that are impossible, this is why it is called Paradox illusion. This includes the impossible staircase and the Penrose triangle.
Ambiguous Illusions: They are images that elicit a perceptual switch that switches between different interpretations. Two of the well-known examples are the Rubin Vase and the Necker Cube.
Depth and Motion Perception Illusion
Illusions can make the individual see three dimensions despite the fact that the image that the eye’s retina is receiving is 2 dimensional. One of the best examples is the Ponzo Illusion. In this illusion, the individual might see that one of the lines lies in a different 3D plane while in fact, the whole image is 2D. The illusion uses the monocular cues of depth perception in order to trick the eye and the brain.
In this illusion, the lines that are parallel lines force the brain to perceive an image that is high in the visual field, this is why the image seems to be in 3D while in fact, the two images that the retina is receiving have the same size and are in the same 2D plane.
Color and Brightness Illusions
In this type of illusions, the constancy of the brightness and color are the ones responsible for the illusion. They force the brain to see that one of the two objects is darker than the other, while in reality, they are the same.
The illusion of contrast different or color can be done when the color luminosity of the area that surrounds the unfamiliar object changes. The contrast of this object will then appear to be darker when the background is black when it is compared to the same object , which can be seen at http://3dcasino.co, but with a white background. This is because the eye automatically compensates for that color contrast depending on the color that is cast on the background of the object.
There are some familiar objects that the brain perceives in a constant size or shape, just like how it perceives brightness and color constancies. For instance, a door is always going to be perceived in a rectangular shape regardless of how the retina receives it. On the other hand, this is not applicable to any unfamiliar objects.
A Unique way to Explain Illusion
Mark Changizi, a researcher who works at the Rensselaer Polytechnic Institute in the city of New York has a very imaginative opinion about illusions. He thinks that they are a result of a neural lag that most people experience during their day. He explains it further by saying that when the light hits the eye’s retina, about 1/10 of a second passes before the individual’s brain can start to translate that signal and transform it into a visual image. Many scientists know about the lag but the matter of how we compensate for it is debatable, as some scientists believe that the motor system of our body modifies our movements instantly in order to compensate for that lag or delay. This is why we do not bump into things because of the lag; instead, our body takes care of it in order to avoid its effects. This is a very interesting explanation, but of course, it is not proven yet.
Optical Illusion Artists
Many artists have built a reputation for working with optical illusions. These artists include Charles Allan Bridget Riley, Salvador Dalí, Gilbert, Marcel Duchamp and Victor Vasarely. There are also some contemporary artists who experimented with optical illusions such as Dick Termes, Patrick Hughes, Rob Gonsalves and Octavio Ocampo.
Read more about the concentric circles illusion here: http://www.reddit.com/r/woahdude/comments/1aqsh0/optical_illusion_four_concentric_circles_pic/