“I can see his face, still, it’s very expressive… only the horse that comes as if out of clouds. The image of the entire scene was very clear, with many details, and yes, the colours were very vivid.” 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. A feeling of a tranquile summer afternoon in a forest, so quiet, so peaceful. “a clearing in a forest, a place bathed in bright sun-shine, and the trunks of trees around. “an urban scenery, like an empty avenue after a rain, large areas covered with water, and the city sky-line reflected in the water surface like in a mirror.” The image did not fill up the entire visual field, it was just like a ‘window’ into that foggy stuff.”
The vision was very clear, but it stayed only for few seconds and disappeared again. Then, all of sudden, I saw a hand holding a piece of chalk and writing on a black-board something like a mathematical formula. It was really boring, I thought, ‘ah, what a non-sense experiment!’ Then, for an indefinite period of time, I was ‘off’, like completely absent-minded. “For quite a long time, there was nothing except a green-greyish fog. Some of the descriptions of hallucinations are really quite striking: The article reviews the sorts of hallucinations reported in during these experiments and discusses what electrophysiology (EEG or ‘brain wave’) studies tell us about what happens in the cortex when these perceptual distortions kick off. It is probably best known for its uses in parapsychology experiments, but it is also used to induce hallucinations and sensory distortions which are much more likely to occur in the absence of clearly defined sensory experiences. The Ganzfeld procedure exposes the participant to ‘unstructured’ sensations usually by placing half ping-pong balls over the eyes so they can only see diffuse white light and by playing white noise through headphones. The cognitive science journal Cortex has just released a special issue on the neuropsychology of paranormal experiences and belief, and contains a fantastic article on hallucinations induced by the Ganzfeld procedure.