An Illusion is a mistake in the perception of a sensory experience. Perception is the process by which organisms interpret and organize information received by the sense organs. An illusion occurs when what the brain perceives differs substantially from the actual qualities of an object or stimulus. Illusions may occur in any of the human senses, including vision, hearing, touch, smell, and taste.

Illusions are common in normal perception and are natural consequences of the way our sensory systems work. Psychologists study illusions because they provide important clues about the functioning of perceptual systems. Magicians rely on illusions to trick and entertain their audiences. However, errors in perception are only considered illusions if they are experienced by a large number of people.

Illusion of Length

Which of the two horizontal line segments seems longer, AB or CD? Although your visual system tells you that AB is longer, a ruler would tell you that its length is equal to that of CD. The slanted lines clearly cause the illusion, because if you removed them you could easily judge the two horizontal lines to be equal.

Click the links below to check out these optical illusions

Color Illusion

The Black Ball Illusion

Motion illusion

Simultaneous Contrast

Spatial Frequency Adaptation

Fraser Spiral