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.
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.