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Spanish Castle Illusion

Simple browser illusion demonstrates short-term visual memory retention

This illusion forces your brain to see color in a black and white photo. It works by first saturating your visual memory with shade and line data, which occurs when you stare at the first picture for more than ten seconds or so. Upon flipping to the second picture, the spectral opposite of the original color data is imposed on the grey lines and shading of the photo.

If the illusions works, it will immediately begin to fade once you move your eyes. This is because a saccade, or a quick lateral eye movement, will effectively "clear" the visual memory buffer with the assumption that the eye is seeking a new pattern to focus on. Even though the visual memory buffer clears with a slight glance in any direction, you will still see a slight fading of illusory effect as the neurochemical saturation in your visual cortex fades.

The saturation and retention of light data in visual memory is responsible for many closed-eye visual hallucinations. Keeping the eyes still and focused in one position is the key to prolonging the duration and saturation intensity of any hallucinatory construct. And even on the most intense psychedelic trip, a saccade or series of saccades will serve to momentarily flush the visual memory buffer and wipe the visual slate clean, as it were.

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Tags : illusion visual memory
Posted on: 2006-06-10 16:06:34