Shamanism is defined as a practice to solve problems in a community by communicating with 'supernatural' worlds in SSC; shamanic states of consciousness. Typical shamanism characterized by 'magical is found mainly in band societies of hunter-gatherers (Winkelman, 1992). Shamans make a journey to other worlds by out-of-body experience (OBE) to contact supernatural power.
According to the hypothesis of evolutionary psychology, the human brain is a result of natural selection under the environment of Pleistocene that Hominid evolved (Tooby & Cosmides,1989). Our brains are optimized to the environment of evolutionary adaptedness (EEA) i. e. nomadic band society. This suggests that the ability to change the state of consciousness into SSC is based on some innate and universal structure of the human brain (Krippner, 1998). In fact, shamanism in a broad sense including mediumistic practice is found in most of human societies. Spirit possession is an altered form of SSC; also, meditation techniques such as yoga and Zen must originate from some kind of shamanic practice in South and East Asia. Even among ordinary people who live in industrial societies, spontaneous shamanic experiences such as OBE during near death experience and sleep paralysis are not rare. This kind of experience also can be induced by entheogenic drugs that have been used in shamanic rituals for thousands of years mainly by indigenous people in Middle and South America.
There is rich experiential evidence of SSC. However, the adaptive value of SSC is not clear. What kinds of information do shamans really process? And why? In this paper, I try to clarify a 'computational theory' (Marr, 1982) of SSC. It is believed that shamans have psychic ability to see a distant place, predict the future, and heal some diseases. Shamans enter into SSC to get the information or power. In general, ASCs have a function to stop the filter of attention while the attention of perception tends to fix on a specific object in 'ordinary' state of consciousness. This makes it easy to aware inner information such as archetypal images stored in the realm of unconsciousness to solve the problem.
In addition, such kind of information may contain 'paranormal' information. Although the results of experimental parapsychology are still controversial, there is evidence that hit rate of ESP experiment increase in the condition of ASC. Shamans may enter SSC to enhance sensitivity to access nonlocal reality. If so, our brain have an inner mechanism to switch the states of consciousness to access to both local reality described by classic physics and nonlocal reality described by quantum physics.
(Proceedings of Toward a Science of Consciousness: Tucson 2000, p. 167. )
