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Isolation tank

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An isolation tank is a dark soundproof tank in which subjects float in salty water at skin temperature. It was devised by John C. Lilly in 1954 in order to test the effects of sensory deprivation. Such tanks are now also used for meditation, prayer, relaxation, and in alternative medicine.

In the original tanks, people were required to wear complicated head-masks in order to breathe underwater; in newer tanks, Epsom salt (1.30 grams per cubic centimeter) is added so that the subject floats with his or her face above the water. However, since the ears are submerged when the subject is in a relaxed position, hearing is greatly reduced, particularly when ear-plugs are also used. When the arms float to the side, skin sensation is greatly reduced because the air and water are the same temperature as the skin, and the feeling of a body boundary fades. The sense of smell is also greatly reduced, especially if the water has not been treated with chlorine.

A therapeutic session in a flotation tank typically lasts an hour. For the first forty minutes it is reportedly common to experience itching in various parts of the body (a phenomenon also reported to be common during the early stages of meditation). The last 20 minutes often end with a transition from beta or alpha brainwaves to theta, which typically occur briefly before sleep and again at waking. In a float tank the theta state can last for several minutes without the subject losing consciousness. Many use the extended theta state as a tool for enhanced creativity and problem-solving or for superlearning. Spas sometimes provide commercial float tanks for use in relaxation.

Shorter sessions may be relaxing and other benefits are claimed by Lilly but have not been confirmed by other scientists. Common reactions to extended sensory deprivation are hallucinations, out-of-body experiences, anxiety, and depression, and some researchers believe this to be evidence of a deep human need for almost constant input of stimuli (the opposite of Lilly's conclusion).

The Isolation tank is also called float tank, floater tank , floatation tank, Samahdi tank, sensory deprivation tank, and John Lilly tank.

Examples in the media

Some of Lilly's books deal with experiences in Isolation tanks. Many accounts from other people can also be found in books as well as on the internet (see Isolation_tank#External Links). Other movies, books, or publications that deal with Isolation tanks or devices that can somehow be compared are the following:

  • Hilary Putnam's "brain in a vat" argument is a thought experiment that deals with the possibility to recognize whether one is a brain in a vat that is sensory stimulated or whether one perceives a more or less objective reality.
  • In the film The Matrix, humanity lives in an illusory simulated reality, called "the Matrix", a construct of the world of 1999, developed by the machines to keep the human population docile whilst they are used as power plants to keep the computers running.
  • On the TV show The Simpsons, Lisa and Homer both used an Isolation tank. Lisa experienced altered consciousness and was led to a better understanding of her father. Homer had a wild ride when his tank was moved while he was still in it.

See also

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