Seeing Things

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Pareidolia is the tendency for perception of a visual stimulus as an object, pattern or meaning known to the observer.

Common examples are perceived images of animals, faces, or objects in cloud formations, or lunar pareidolia like the Man in the Moon or the Moon Rabbit. The concept of pareidolia may extend to include hidden messages in recorded music played in reverse or at higher- or lower-than-normal speeds, and hearing voices (mainly indistinct) or music, in random noise such as that produced by air conditioners or fans.

Pareidolia was at one time considered a symptom of psychosis, but it is now seen as a normal human tendency. Scientists have taught computers to use visual clues to "see" faces and other images.