Its a psychological phenomenon where the brain perceives any random and vague stimulus as meaningful stimulus. For example: Interpreting the shapes of clouds as birds or animals

So basically its an illusionary sensory perception. There is a mismatch or error between the actual stimulus and the interpretation of the stimulus (internal representation). Pareidolia is an excellent way to understand the mechanism in which the signal is sent to the brain (bottom up input) and how brain modulates the signal (top-down modulations)

The Big Book of Brain Games: 1000 Thinks of Art, Mathematics and Science Paperback by Ivan Moscovich (Author)

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