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Subject 4, a 23-year-old man, reported seeing images as well as flashes of light within a few hours of being blindfolded.
He saw outlines of puzzle pieces that, while moving, “warped into other amorphous shapes” and transformed in color from white to orange to red. He saw these perceptions “when I think about my sense of sight.” On day four, he reported seeing a triangle with bold dots at each vertex of the triangle and “a large X with a light shining underneath it.” Immediately before the report, the subject was engaged in a tactile stimulation task in which he was asked to discriminate five raised dots arranged in the form of an “X” on a domino piece.
The complex hallucinations seem in many cases to pop up because of an association to another perception. For example the above quoted person saw an X after feeling an X with his fingers.