Isolation tank

An isolation tank (also commonly known as a sensory deprivation tank) is (ideally) a lightless, soundproof tank in which subjects float in salty water (denser than the human body) 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.

The isolation tank is also called float tank, floating tank, floater tank, floatation tank, Samadhi tank, sensory deprivation tank, REST tank (Restricted Environmental Stimuli Therapy), and John Lilly tank.

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).

More extreme uses of the tank involve the subject taking varying doses of hallucinogens, such as LSD, and spending prolonged periods in the tank (up to tens of hours) at a time, an approach pioneered by Lilly himself – though he claims to have tried LSD in the tank only after 1964, when the drug was still legal, a decade after his first experiments with the tank itself.

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. Other movies, books, or publications that deal with isolation tanks or devices that can somehow be compared are the following:


 * Paddy Chayefsky's novel Altered States and the film based on it deal with a scientist who is able to reach different states of consciousness by use of drugs and the isolation tank.


 * Richard Feynman, a famous physicist, writes about his experiences with sensory deprivation in a floatation tank in one of his popular books, Surely You're Joking, Mr. Feynman!. Feynman was invited to try the isolation tank at John Lilly's home after Lilly attended one of Feynman's popular lectures on quantum mechanics.


 * Hilary Putnam's "brain in a vat" argument is a thought experiment that deals with the possibility of recognizing 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 while they are used as power plants to keep the computers running.


 * On the TV show The Simpsons, Lisa and Homer both use an isolation tank. Lisa experiences altered consciousness and is led to a better understanding of her father. Homer has a wild ride when his tank is first removed by repo men, falls out the back of their truck, is buried by the Flanders (who believe it to be a coffin), sinks through thin earth into a sewage drain, is carried out to sea by a sudden gush of sewage water, washes up on the beach, and is then returned by Chief Wiggum to the store from which it was originally repossessed.


 * In the film Daredevil, the main character, Matt Murdock, while blind, has extraordinarily heightened senses (particularly hearing) that make it impossible for him to sleep without an isolation tank to shut out the outside world.

Books on the Subject

 * The Book of Floating. Hutchison, Michael
 * Tanks for the Memories: Flotation Tank Talks. Lilly, John C. & E.J. Gold.
 * The Deep Self: Profound Relaxation and the Tank Isolation Technique. Lilly, John C.
 * The Center of the Cyclone. Lilly, John C.
 * The Scientist: A Metaphysical Autobiography. Lilly, John C., M.D.