“When one or more senses are restricted, the sensitivity of the others senses is expanded.” – The Book of Floating by Michael Hutchison

The floatation tank makes use of this sensory deprivation effect to bring about a gentle, pleasant, controllable, and temporary shift in consciousness in anyone who floats. This shift in consciousness is healthy, educational and can be manipulated, explored and used in such a way as to cause positive changes in attitude, physiology, and behaviour  that persist even after the float.

While floatation tank is the best modern tool for cutting down the amount of external stimuli, humans have been using a variety of tools and techniques to achieve sensory deprivation for many years. Here are just some of them:

• Preparation for the Hunt. Back in the day it was a regular practice for men to withdraw from normal activities and “purifying” themselves through fasting, silence, steam baths and isolation to prepare their mind and body for a hunt of war. They believe that this sensory restriction improves their hunting abilities. Recent tests have demonstrated that short periods of sensory deprivation increase senses of smell, taste, sight and hearing.
• Rites of Passage. Back in history many cultures had a ceremony marking the passage from childhood to adulthood. Commonly these ceremonies included some sort of sensory deprivation as a part of transition to adult society. For example in many cultures young boys were confined for days of weeks to darkened huts, undertake fasts or leave the village to stay alone in the wiled for a long period of time. Whatever sensory deprivation technique used, it meant to young people more open to new experiences and new wisdom by making them sensitive and aware.
• Spiritual Withdrawal. In every culture some sort of sensory deprivation experience has been considered essential in the training of spiritual leaders. Shamans, witch doctors, monks, priests, yogis, mediums and other spiritual seekers often experienced periods for total silence, fasting, darkness. Whether it was isolation of a cave, a desert or a monastery; or the mental equivalent of such isolation attained through mediation or a payer.
• Creative Isolation. Many moments or creative illumination, insight, or revelation have occurred in circumstances in which sensory input has been reduced in some way. In fact, one of the essential elements of all creative thought is concentration gained through some sort of sensory isolation.
• Isolation on the Couch. One of the greatest values of traditional psychotherapy derives from its sensory deprivation effect: as the patient sits in a relaxing position on a couch, with the therapies positioned behind, there is a little visual or auditory stimulus to distract the patient from a free-associative state.

It is clear by now that the use of sensory isolation has a long history. Sensory restriction is an effective way of turning toward reality, of increasing our sensitivity to and awareness of the world as it is. People who emerge from floatation tank are often delighted to find that the world seems to have changed while they were away. They speak of seeing things anew, and describe the world as fresh, glowing, bright and more vivid.

– Summary of Less is More – The Sensory Restriction Tradition from The Book of Floating by Michael Hutchison