Ganzfeld effect

How it works

Ganzfeld is German for “whole field”. A ganzfeld is a visual field with no edges, no detail, and the same colour everywhere¹. Snow blindness in a blizzard is a natural one. So is a thick fog. Polar explorers and pilots flying in whiteout describe the same experience¹.

The visual system works by comparing. It reports edges, changes, and differences. Give it a field with no differences and it has nothing to report. After a few minutes the signal from the eyes is effectively treated as noise. The brain then does what it does in the dark: it amplifies its own activity and presents that as images¹.

The first thing most people notice is that the colour vanishes. A red ganzfeld goes grey. Then come lines, moving specks, and blotches of colour. Some people see geometric patterns. With more time, some see faces, animals, or scenes, and hear sounds if there is white noise in their ears too¹. The whole effect is close to prisoner’s cinema, but it takes minutes instead of days, because the eyes are open and receiving a flat signal rather than none¹.

The set-up was used in the 1970s in parapsychology experiments that claimed to test telepathy². The results are disputed and have not been replicated to most scientists’ satisfaction².

Try it

1. Cut a ping-pong ball in half. Tape or hold one half over each eye. Cotton pads work too.
2. Sit facing a lamp with a plain shade, or a red light if you have one. The light should be even and not too bright.
3. Put on headphones playing white noise, or static from a radio.
4. Keep your eyes open and relax. Do not try to see anything.
5. After 5 to 15 minutes the colour fades, then patterns or images appear.
6. Stop whenever you like. Everything goes back to normal as soon as you take the balls off.

History and culture

The effect was studied in the 1930s by the psychologist Wolfgang Metzger¹. Some meditation and mystical traditions use featureless fields of sky, snow, or light in a similar way, and the visions reported in them may be the same effect¹.