The Ganzfeld effect (German: ‘complete field’) is a phenomenon of visual perception caused by staring at an undifferentiated and uniform field of color. The effect is described as the loss of vision as the brain cuts off the unchanging signal from the eyes. The result is ‘seeing black’ – apparent blindness. In the 1930s, research by psychologist Wolfgang Metzger established that when subjects gazed into a featureless field of vision they consistently hallucinated and their electroencephalograms changed. The Ganzfeld effect is the result of the brain amplifying neural noise in order to look for the missing visual signals. The noise is interpreted in the higher visual cortex, and gives rise to hallucinations. This is similar to dream production because of the brain’s state of sensory deprivation during sleep.
The Ganzfeld effect has been reported since ancient times. The adepts of Pythagoras retreated to pitch black caves to receive wisdom through their visions, known as the prisoner’s cinema. Miners trapped by accidents in mines frequently reported hallucinations, visions and seeing ghosts when they were in the pitch dark for days. Arctic explorers seeing nothing but featureless landscape of white snow for a long time also reported hallucinations and an altered state of mind.
The Daily Omnivore 
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