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Illustration by Ruth Basagoitia

The ganzfeld effect happens when your brain is starved of visual stimulation and fills in the blanks on its own. This changes your perception and causes unusual visual and auditory patterns. It can even lead to hallucinations.

Psychologist Wolfgang Metzger introduced the concept of the ganzfeld effect in 1930. “Ganzfeld” is a German word that means “whole field.” It refers to an unstructured, uniform space covering your entire visual field.

Experiments on the ganzfeld effect have been used to investigate telepathy and hallucinatory states. Some people do it just for the experience.

Read on to learn more about the ganzfeld effect, whether it’s safe, and things to consider before attempting this experiment.

If you can see, your brain uses visual input to make sense of the world. To create the ganzfeld effect, you have to deprive your brain of the information it needs to perform this task.

With no incoming signals, your perception of brightness slowly decreases. This is called the fade out.

As retinal cells become more active, you might start to see the blood vessels in your eyes. In a few minutes, things may turn gray. Then you might see zigzag lines, dots, or a blob of color. The full effect usually takes 5 to 7 minutes.

Longer exposure may produce stranger results. Your brain is frantically seeking outside stimuli. Finding none, the higher visual cortex starts amplifying available information, generating visual and auditory hallucinations.

It’s similar to what would happen if you were lost in a blinding snowstorm, seeing nothing but a wall of white.

The ganzfeld effect came to public attention when it was used to research extrasensory perception.

In telepathy experiments, one person acts as the receiver and is exposed to white noise and a homogeneous red light. Another person, the sender, attempts to relay information to the receiver.

With mixed results, these investigations are controversial and have been fiercely debated.

The ganzfeld effect has also been used to research hallucinations. It has provided information on how our senses, especially vision, function to detect change.

Some people look at it as a way to induce visual phenomena and hallucinations without taking dangerous drugs. Some use it as a form of deep meditation.

For most people, it has no practical use, but it can help satisfy your curiosity about how the human mind functions.

To achieve the ganzfeld effect, you have to create that all-important uniform field of vision. This takes attention to detail.

One way to do this is to cut a Ping-Pong ball in half. You’ll use each half to cover a different eye. The balls should be clean, with no spots or writing. The halves should be tailored to your face so there are no gaps to let light in. You can use tape or adhesive to make sure they don’t move.

Another way is to cut plain white paper into the shape of an eye mask. Cut an elastic band and staple the ends of the band to each side of the mask. You’ll use this to keep the mask over your eyes. Glue cotton balls around the border of the mask to keep light from entering.

You can even buy ganzfeld goggles.

However you do it, light reaching your eyes must be equal in all directions. The room should have no shadows or flickering light. Some people choose to shine a bright light, usually red, to flood the room and keep the lighting uniform.

Then you’ll need noise-cancelling earphones, uninterrupted static, or some form of white noise.

Put the earphones and eye coverings on, but keep your eyes open. Then settle in, be still, and let the experiment begin.

Producing the ganzfeld effect is safe for most people.

While harmless for most, the experience can be disorienting and too intense for some people.

With exposure of 10 to 20 minutes, you may experience intermittent loss of vision. Some people can’t even tell if their eyes are open or closed. These effects can be unsettling, but they’re temporary.

It’s also possible to experience disturbing hallucinations. While this may actually be the goal for some people, hallucinations can be frightening. You shouldn’t try this experiment if you have a mental health condition that could be exacerbated by sensory deprivation or hallucinations.

A ganzfeld is an unstructured, uniform space over your entire visual field. By altering your sense of sight and sound, you deprive your brain of the sensory input it needs to understand the outside world.

As your brain searches for information, it begins to fill in the missing pieces, which can produce visual and auditory hallucinations.

If you want to find out what your brain will conjure up, you can try to produce the ganzfeld effect on your own. It’s not harmful for most people.

Keep in mind that the experience is subjective. This means it’s different for everyone and may not live up to expectations.