Illusion
It is a wrong perception or a mistaken perception. It is defined as an immediate apprehension of an object as we like it and not as it is. The perceptual process involves and interpretation of the sensory experience in the light of our past experience, present attitude organic needs etc. Consiquantly if the interpretation is done wrongly the stimulus perceive will be wrong. Such a phenomenon is known as illusion. The classical example is our perception of rope as a snake in dark. The stimulus is like the one coming from a snake and it is quite real and objecting because of the similarity between the two, we perceive a rope as a snake in the night as guided by our past experience and fear. In illusion there is always an objective reality but it is mistaken. Thus illusion is normal and universal phenomenon.
Types of illusion
In order to understand how illusions are caused the psychologist have studied illusion by making use of a number of geometrical figures which cause illusions.
Muller lyer illusion
In the illusion there are two straight lines of equal length one is bound with a pair of arrow heads at both the ends and another line has feather heads at both the ends. Though both the lines are equal in length, the line with arrow heads appears shorter than the line with feather heads. This is nothing but optical illusion. This illusion is due to the context of the arrow heads and feather heads attached to the lines. Generally there is a tendency to under estimate their feather head line. This is due to the fact that while perceiving the arrow head line our vision is restricted on the other hand we tend to extend our vision beyond what is given while seeing the feather heads line.
Horizontal vertical illusion
In this the verticals line is always drawn from the midpoint of the horizontal line in a right angle position. Though the two lines are of equal length the vertical line appears longer than the horizontal line by virtue of its position. This is because the movement of eyes along the vertical line is more tired than the movement on the horizontal line. Naturally the vertical line looks shorter than what it is. Example the horizontal line looks shorter than what it is. Another reason is that the horizontal line is cut at the intersection which makes it look shorter than vertical line.
Illusion of movement or ( Phi- phenomenan )
Perceiving movement is one of the characteristic of perception. It is an innade nature of human vision though perceiving movement is natural perceiving apparent movement of an object is known as illusion of movement or phi- phenomenon. What we see on the screen in a cinema theatre is not the real movement but a series of still pictures projected on the screen at a particular speed that is 20 to 25 pictures per second the neon light advertisement are also based on this principles..............Read
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