A visual illusion or an optical illusion will be characterized by images perceived visually that will differ from the reality which must be objective. The information that will be gathered by the eye will be processed in the brain just to give the precept that will not be in concordance with the stimuli that will be at hand.
< -300x250 Medium Rectangle - center->
There are three types of optical illusions, the ones that will create the images that will be different from any objects that help in making it, the ones that have an effect on the brain and the eyes and those are the psychological ones from movement, color, tilt or brightness and the illusions where the brain and the eyes make interferences that will be unconscious and those are the cognitive ones.

The physiological illusions like the afterimages that will follow bright lights or that will be adapting stimuli of longer patterns are assumed to have the effects on the brain or the eyes with excessive stimulation like movement, color, tilt or brightness. The main theory is the fact that stimuli will have individual neural and dedicated paths in many early stages on the visual process and the stimulation that will be stimulation that will be repetitive and only a few or mainly one channels will cause this imbalance physiologically speaking then the alter perceptions.

One of the most known optical illusions is the Mach Bands illusions and the Hermann grid illusion that can be explained by just using an approach used biologically. The inhibition that will be lateral, where in the field of receptiveness in the retina where the dark and the light receptors are there active and ready to do their job, has been explained why when you see this picture you may have the impression that you will see white and dark spots and you will have the impression that the image will move.

This will be very tiring for the eyes thus you can’t watch it too much because the brain and the eyes cannot be in concordance with the information that it gets. Once the receptor will be active it will inhibit any other receptors and this will create the contrast, highlighting any other edges and in the optical illusion of Hermann the gray spots will appear at the intersection because of the response of the inhibitory.

The cognitive illusions lead to the unconscious interferences and are assumed to arise by the interactions between the stimuli. This category of optical illusions is subdivided in three main divisions : the ambiguous illusions that will be pictures or many objects that will switch  in the interpretations that will be alternative. An example of this kind of illusions is the Necker cube that everybody knows and another good example is the Rubin vase, the distorting illusions that will be characterized by many distortions or curvature, length or size. A very good example of such a cool optical illusions is the Café wall illusion or the Muller-Lyer illusion.

The paradox illusions generally are made by objects that appear impossible or paradoxical for instance the Penrose triangle or the staircases that seem impossible.  A good example of such cool optical illusion is the M. C. Escher’s Ascending and Descending or the Waterfall. This triangle is an well known illusion that is made itself dependent on the fact that misunderstanding the information of the adjacent edges that will join. The fictional illusions may be defined by the perception of the objects that will be genuinely not the same for every single observer, like induced by hallucinogen or by the schizophrenia.

The best term for these ones is the one of hallucinations.To organize sensations that are incoming will help to make sense of the world and it is quite necessary to organize the information that will be meaningful for the interpretation of the brain. So, you will know what you are seeing, touching or feeling.

The psychologist of Gestalt stated that this thing is done in one way by perceiving sensors that will be individual and with the altogether stimuli making it a quite meaningful whole. This organization tried to explain many illusions for instance the Rabbit-Duck illusion where the image will switch to back and forth to a duck or a rabbit and you just can’t tell which one is the animal being a reversible image. The theory of the researchers was used just to explain the contours of the illusions for instance a triangle that is floating which does not exist but it is seen. The brain has the tendency to create images and shapes just to make a ‘whole’ of the information that is in front of the persons eyes.

Because of this, the organization was created and Gestalt in German means ’shape’ and ‘form’ but there are other explanations for instance of the Kanizsa Triangle that will be based on the psychology of evolution that states that it is important to see shapes and sizes just to survive. The principle behind other optical illusions that will include impossible objects is the usage of the organization of perception that will create stimuli. In the brain it will only make sense if the information turns out into symbols and shapes and it will be easier to make it like a puzzle and thus discovering which piece is missing from the image.

Based on the ability on every individual to see likely in three dimensions, illusions are much easier to understand on this concept although the image that will hit the retina will be only two dimensional. For instance the Ponzo illusion is a very good example of a cool optical illusion that will use the monocular depth cue of perception just to fool the eyes. In this illusion the parallel lines will tell the brain the fact that the image will be higher then the actual visual field that will be farther away thus the brain will perceive the image to be much larger then the actual size but nevertheless the images that will hit the retina will have the same size. The optical illusions that will be seen in false perspective will put out assumptions that will be made on the cues of monocular of the deepness of perception.

Such rules are exploited by the M. E. Escher that is painting the Waterfall and the understanding of any person on a physical field will surely create the illusion. For the sensory illusions the main features will be the motion perception and the depth perception. Any film animation will be based on the illusion that the brain will only receive various images that are produced rapidly as a picture in motion. We can perceive a large object for instance like an airplane that will move slowly then other smaller objects like cars that will move faster.

Another example on how the brain will perceive motion is the Phi phenomenon which is created for instance by blinking lights on a very close succession. Sources of optical illusions are the perceptual constancies. The brightness and the color constancy will be responsible for the fact that any familiar object will always appear with the same color without taking into count

The illusion of color will be created by the luminosity or the colors of the surroundings on any familiar object that will be changed from the environment. The contrast will appear much darker then it actual is but the brightness level will appear the same and this is an extraordinary event that will trick the mind in seeing shadows. The eyes will try to compensate for the lack of color contrast and this will only depend on the surroundings and its contrast and color.Shape and sizes are also very important because the brain will understand familiar shapes and sizes like in the case of the colors.

An ordinary door will be perceived as a rectangle regardless the color or other ornaments that will be on it. For the unfamiliar objects the rule of shape constancy is not applied because the perspective has been changed and thus memory and perceive will not be applied. For instance the cool optical illusion of the Shepard of the on going changing table is based solely on the distortion theory with the shape constancy.

From the Renssalaer Polytechnic Institute in New York, the researcher Mark Changizi stated that optical illusions are the outcome of the neural lag which the majority of the humans while they are awake.  When the retina it is hit by the lights, one tenth of a second will go by before the brain will have the chance to translate the signal into perception on the visual field from the world. Many scientists have known about the lag theory but they debated if this is the real issue because humans try to compensate for the delays on the neural field and they will generate images just to fill the whole.

For the example there is a very cool optical illusion named Hering illusion that will look like a bike spoke that will be around a central point, but it will not be actual moving and the figure will be static and we will misperceive the lines that will be straight as to the curved lines.There are many cool optical illusions out there and trying to understand them will make you understand better on how your eye sight and your brain work.

An optical illusion is based on the difference between the perception of an image and the objective reality. The information which perceived by the eye is transmitted to the brain and there it is analyzed and it is given a precept, which sometimes, doesn’t fit with the reality. There are three types of illusions: literal optical illusions, which make the perceived image seem different from the real objects, physiological illusions, which happen as an effect of the excessive stimulation on the eyes and brain, and cognitive illusions where the brain and the eyes make inferences unconsciously.
<-300×250 Medium Rectangle – center->
The American Flag illusion is quite well known and many people know what should happen, but it still remains cool. Stare at the center of the image for at least 15 seconds (you can try more to enhance the effect), and after this, look at a white area on your computer screen, a wall or a  blank paper.You should try it again, but not looking in the center. Try to move your eyes from left to right, and you will see that you can not focus on the image, and the flag will continuously be in your vision field. It has been burned on the retina, and when you will try to focus and get it to stop from moving, it will move more. It is similar as watching the sun or a bright light. This is a perfect illusion for both adults and children.

What do you see written here? There are people who see first the word “evil”, but other people see the “good” part in the beginning and then they realize the other word.

The following illusion will show you the ability of the brain to fill in spaces with recognizable patterns, and to make interrupted things continuous by completing them with already known, familiar segments.

One of the funniest optical illusion is this one. Try reading the text in the following image from the distance you are now at, and then go farther. You will see more clearly the sentence written, and you will understant you couldn’t read it in the beginning.

The following image shows that the brain that human brain is “smarter” than we thought, and it helps us read and understand texts, even if the letters and not in the natural order.

Try thinking about and saying aloud the ink color of each word in the following image! How quickly can you do that?

You can have a lot of fun with these optical illusions, and you can show them to other people and make fun of them, test their vision and their brain agility!