Sensory Deprivation Tanks
"In the province of the mind what one believes to be true, either is true or becomes true within certain limits. These limits are to be found experimentally and experientially. When so found these limits turn out to be further beliefs to be transcended. In the province of the mind there are no limits. However, in the province of the body there are definite limits not to be transcended." - John C. Lilly, Inventor of the Sensory Deprivation Tank
Across various cultures throughout history, humans have found various ways of achieving heightened states of consciousness, including drumming, controlled hyperventilation (holotropic breathing), psychedelics and, of course, meditation. We’ll explore these other methods in future posts, but for now, our attention turns to a device create more recently specifically to induce a meditative state: the sensory deprivation tank, also known as an isolation or float tank.
It seems every biohacker out there is using these devices, including Joe Rogan and the Navy SEALs. But what’s actually going on in your brain during a float session?
When I first set foot in a float tank, I thought I was going to lose my mind. There’s no light, sound, feel (water is perfectly body temperature), nor smell, hence the name “sensory deprivation.” You’re suspended in salt water, so even the tug of gravity has been eliminated as you float weightlessly. I felt like a brain in a jar, with no physical body attached.
The whole point of sensory deprivation is that without all of the external stimulation, your mind and body relax. Your brain enters a theta wave state, just like deep meditation, and the “rest-and-digest” parasympathetic nervous system gets activated.
The first float tank was designed by physician and neuroscientist John Lilly in 1954 to study the origins of consciousness; he hypothesized that depriving a human of sensory data could isolate the original state of the mind. Lilly was considered by many in the scientific community to be pretty “out there” with his research. His eccentric studies (he claimed he could talk to dolphins using his flotation tank) inspired Hollywood movies The Day of the Dolphin and Altered States.
Regardless of Lilly’s often unscientific pursuit of science (he was also good pals with notorious Harvard psychologists Richard Alpert and Timothy Leary), his invention undoubtedly provides practical application and potential therapeutic value. The Navy SEALs, for example, use the chambers to treat concussions and reduce their language learning from 6 months to 6 weeks by blocking out all other senses. The reason for this accelerated learning is rather obvious when you look at how much information processing our senses normally consume:
Eyes - 10,000,000 bits per second
Skin - 1,000,000 b/s
Ears - 100,000 b/s
Smell - 100,000 b/s
Taste - 1,000 b/s
(Of all of this data, only 50 bits per second can be consciously processed.)
With the elimination of external stimuli, the central nervous system’s workload is significantly reduced (by up to 90%, according to one article I read and admittedly forgot to document). I’d theorize that the sensory dep chamber frees up a lot of bandwidth in your brain for other types of activity, like learning, processing emotional baggage, and generating novel ideas.
Although more research is needed, sensory deprivation sessions also show promise for reducing stress, improving sleep and potentially mitigating a host of mental health issues. Studies have also demonstrated enhanced psychological and physical recovery time after strenuous activity. [2,3]
If you’re claustrophobic or have a family history of psychotic disorders (many people experience hallucinations during sensory dep sessions), you might avoid this experience. Float tanks are in fact very low-risk or I wouldn’t be recommending them, but always better to err on the side of caution. Otherwise, floating could be worth experimenting with as a supplementary mental wellness hack.
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 Kjellgren, Anette, and Jessica Westman. "Beneficial effects of treatment with sensory isolation in flotation-tank as a preventive health-care intervention–a randomized controlled pilot trial." BMC complementary and alternative medicine 14.1 (2014): 417.
 Driller, Matthew W., and Christos K. Argus. "Flotation restricted environmental stimulation therapy and napping on mood state and muscle soreness in elite athletes: a novel recovery strategy?." Performance Enhancement & Health 5.2 (2016): 60-65.
 Morgan, Paul M., Amanda J. Salacinski, and Matthew A. Stults-Kolehmainen. "The acute effects of flotation restricted environmental stimulation technique on recovery from maximal eccentric exercise." The Journal of Strength & Conditioning Research 27.12 (2013): 3467-3474.