Probably best known as a tool for parapsychology studies, the Ganzfeld experiment helps a person achieve a state of sensory deprivation. It can easily be put together at home by taping half a ping pong ball over each eye so you can only see diffuse white light and play white noise through headphones.
This simple setup can induce hallucinations and sensory distortions. The effect has been reported for thousands of years. Pythagoreans retreated to pitch-black caves to receive wisdom through their visions. Prisoners kept in darkened solitary confinement cells and miners trapped by accidents in mines frequently report visions, hallucinations, spirits and ghosts. Arctic explorers, seeing nothing but a featureless landscape of white, have reported visions. People with severe blindness, or those with Charles Bonnet syndrome or Visual release hallucinations, enter into a world of these visions.
The hallucinations reported in these experiments can be vivid and striking:
“I could hear music, there was music coming from the right side above, then moving around to the left side, dropping below me, and behind me.”
“A friend of mine and I, we were inside a cave. We made a fire. There was a creek flowing under our feet, and we were on a stone. She had fallen into the creek, and she had to wait to have her things dried. Then she said to me: ‘Hey, move on, we should go now.’”
“All of sudden, I saw a hand holding a piece of chalk and writing on a blackboard something like a mathematical formula. The vision was very clear, but it stayed only for few seconds and disappeared again. The image did not fill up the entire visual field, it was just like a ‘window.’”
“An empty avenue after a rain, large areas covered with water, and the city skyline reflected in the water surface like in a mirror.”
“A clearing in a forest, a place bathed in bright light. A feeling of a tranquil summer afternoon in a forest, so quiet, so peaceful. And then, suddenly, a young woman passed by on a bicycle, very fast, she crossed the visual field from the right to the left, with her blond long hair waving in the air.”
“In the right side of the visual field, a man suddenly appeared. He was all in black, had a long narrow head, fairly broad shoulders, very long arms and a relatively small trunk. He approached me, stretching out his hands, very long, very big, like a bowl, and he stayed so for a while, and then he went back to where he came from.”