What is Optical Illusion?

What we see is not always what we perceive. When there is discrepancy between what we see and what we perceive, then it is optical or visual illusion. In other words, the final outcome our perception is different from what is actually there in reality. There could be number of reasons for optical illusions. A lot of interesting works and studies have been conducted in this field. Optical illusions are categorized under three types:

Literal optical illusion
Physiological optical illusion
Cognitive optical illusion

Our brain is programmed to make inferences from our past experience and this is one of the major reasons for optical illusion. Our brain tends to fill in the gap through a serious of presumptions based on past experience. This happens in our daily life and every hour of our life. All the things that we see around us and perceive are one big bundle of optical illusions. You must know that this is a much wider area than what you thing, it is not just some clever images that you see are objects of optical illusion. We run our entire life based on a series of optical illusions.