g Tum-mo heat meditation
Preparing for a lecture on homeostatic mechanisms, I came across a surprising phenomenon, g tum-mo heat meditation, that raises an interesting question about human enculturability. Homeostatic mechanisms are those that maintain our bodies (or our lives) in a state of balance between two (or potentially more) extremes that might be fatal. Insofar as some of our homeostatic mechanisms are controlled by the central nervous system and involve behavior, they fall within the purview of psychology, and I treat the body temperature, thirst, and hunger regulation cycles in my Introduction to Psychology class. The phenomenon that surprised me pertains to the first of these systems.
A Buddhist monk has his vital signs measured as he prepares to enter an advanced state of meditation in Normandy, France. During meditation, the monk's body is said to produce enough heat to dry cold, wet sheets put over his shoulders in a frigid room (Photo courtesy of Herbert Benson).
Body temperature regulation is quintessentially cognitive in nature. We have heat sensors distributed throughout our bodies. The heat sensors in the body's periphery-let's use the feet as an example-are a suite of neurons, each of which has a slightly different temperature at which it slows its activity. By detecting which neurons are normally active and which have slowed, the central nervous system can tell the temperature of the feet. The effectors for changing temperature are also located in the extremities: control of little hairs, blood vessel constriction, and shivering are all local. Despite the fact that both the detectors and effectors are local, the detectors do not communicate directly with the effectors: instead, they send their signals all the way up to a center in the brain, and then the brain sends the signal all the way back down to the effectors in the feet. It is cognitive in nature in that the whole thing is an information detection and communication system, and it is so automatic that it is often called a reflex.
The reason that the brain must meddle in the affairs of the feet is because most of our body temperature management is behavioral, and behavior requires centralized coordination. If my feet were just going to shiver, they could do that on their own-or they would be able to if the connections were there. But if I am going to put on socks, then my brain has to get involved. There can't be anything automatic or reflexive about putting on socks, because doing so has to be coordinated with other behavioral priorities. If the building is on fire, one ought not stop to put on socks.
Now this is where things start to get weird.
Monks in Tibet-that mountainous country so blessed with oddities-can consciously raise the temperature in their hands and feet 6-7º C (10-12º F), in laboratory conditions (Benson, et al., 1982). There appear to be several methods of g Tum-mo meditation, as described by Alexandra David-Neel (1965), but all seem to involve the visualization of oneself filled with fire. Whether, for adepts, such visualization is necessary for control of body temperature is not clear to me, because Benson reports that one of his research participants began undergoing g-Tummo changes every time he sat down. Monks will even have little contests where they spend a night on a river bank, repeatedly draping themselves with wet sheets, and seeing who can dry the most. I get cold just thinking about it.
It presumably takes some time to develop this ability, but apparently not so much that it is rare in Tibet: David-Neel claims that most Tibetans have the knowledge of how to do it, and that they put it to practical use.
What interests me about this is not simply that the mind has considerable control over the body-that is a familiar refrain from many areas of research. What interests me is that we could have this ability and not know it unless someone teaches us. No one had to teach me how to shiver, or to raise little body hairs, or to contract my blood vessels. So, if we are capable of mentally warming our extremities, why should we not automatically know how to do it? It seems that boundary in the temperature regulation system between what is automatic and what is susceptible to willed intervention is strangely situated.
Bibliography
Benson, H., Lehmann, J. W., Malhotra, M., Goldman, R. F., Hopkins, J., & Epstein, M. D. (1982). Body temperature changes during the practice of g Tum-mo (heat) yoga. Nature, 295, 234-236.
David-Neel, A. (1965). Magic and mystery in Tibet (New ed.). New York,: University Books.
Olivier Morin 9 October 2009 (14:04)
Thank you Brian, for another exciting post. I am not convinced at all by Benson's claims - although I have to admit that I know them only from reports in the scientific press and interviews. Here are a few problems : (1) He received money to attempt a better controlled replication in 2002, which took place but did not seem to yield publishable results. (2) When Benson claims that the monks were able to raise the temperature of their finger by as much as 8.3° C., I wonder what baseline is being considered for comparison. After all, changes in temperature take place at the surface of my fingers all the time... (3) Benson is pushing the view that special thermoregulation is a rare feat that requires a lifetime of training in meditation, but many others disagree, to begin with your citation of David-Neel. Amateur european practitioners of extreme heat regulation are to be found everywhere on youtube. They are sometimes dismissed as crooks or hoaxes, but obviously this suspicion would apply elsewhere too. (4) The capacities of Buddhist monks have not (as far as I know) been compared to that of ordinary mountain-dwellers or explorers used to extreme temperatures, or even ordinary folks asked to concentrate on elevating their bodily heat (who knows what they might do?). So, even if you grant the existence of the phenomenon, the link with meditation remains unproven. Your anecdote about the monk who couldn't help getting hot when sitting suggests that even conscious, voluntary control is not of the essence of the phenomenon - I would suggest something like automatic metabolic adaptation to extreme climate. (5) Lastly, I have a suspicion (perhaps groundless) that in this area, many unsuccessful attempts are made, and only successful ones are recorded. This is nevertheless a fascinating area of enquiry.
Brian Malley 13 October 2009 (13:11)
Thanks, Olivier, for flagging these concerns. I came across no debate about it in the scholarly literature (maybe I just missed it), so I did not know there was reason to doubt Benson's claim.
Christian Kleineidam 20 October 2009 (23:30)
From my own limited experience with meditation, a bit of heat production isn't something that difficult to achieve. While I certainly won't achieve a feat like increasing it by 8 degrees it's enough to stay warm while being naked and having an open window with single digit degrees outside. The thing even happens when I felt cold while wearing clothes with a closed window before I started meditation. I have seen the effect with both self driven meditation and with guided meditation from a tape (or hypnosis however you want to call it). I would guess that a good hypnotherapist could increases the body temperature of anyone (ordinary folk) who is highly suggestible to hypnosis simply be giving suggestions to relax and suggestions to feel more warm in a hour or two (maybe even less). From there I would create the hypothesis: Producing heat that way seems only be possible when there's deep relaxation. Clear rhythms. No unconscious uncontrolled movements that are noise. Getting rid of a bunch of chaotic unconscious processes that happen in the vegetative nerve systems just isn't something that your unconscious can do in the same way that it can just fire up a reflex to raise body hairs or contract blood vessels. It's not about starting a process but about shutting of processes that produce noise. For that reason it can't be fired by simple reflexes.