Yes, you are correct. In the Ganzfeld experiment, the use of ping pong balls or other materials that partially block vision is an essential component. The purpose of the ping pong balls or white paper is to create a uniform and unpatterned visual field, which, combined with reduced sensory input, can potentially lead to hallucinations or altered states of consciousness.
During the Ganzfeld experiment, participants typically sit or lie down comfortably, with half of a ping pong ball placed over each eye or with white paper covering their eyes. This creates a diffuse, featureless visual input, which can cause sensory deprivation and lead to the brain generating its own visual experiences.
The pressure of the ping pong balls on the eyes is not primarily responsible for the hallucinations in this experiment. Instead, it's the combination of sensory reduction (uniform visual field) and the brain's natural tendency to fill in gaps in sensory input, which can lead to hallucinatory experiences.
The Ganzfeld experiment is not without controversy, and the results have been mixed in scientific studies. Some individuals report hallucinatory experiences, while others may not experience anything out of the ordinary. Additionally, the reliability and validity of the results have been questioned.
It's important to note that conducting such experiments, especially without proper supervision or understanding of the potential risks, is not recommended. The altered states of consciousness induced by sensory deprivation can have unpredictable effects on different individuals and may not always be safe. If you are interested in exploring altered states of consciousness or hallucinations, it's best to do so under the guidance of trained professionals or experts in the field.