Consciousness and Unconsciousness: Cross-Cultural Experience . In the West, consciousness was a topic of considerable interest in 19th-century philosophy and the early development of psychology. The philosopher John Locke, in his Essay Concerning Human Understanding, defined consciousness as "the perception of what passes in a man's own mind." William James in The Principles of Psychology, spoke of the "stream of consciousness," emphasizing the continuous and variable nature of mental content, thus viewing consciousness as a process. James also distinguished "normal, waking" or "rational" consciousness from other types. To study consciousness, 19th-century psychologists proceeded by means of "introspection." This method, deemed unscientific and unreliable because it produced inconsistent findings, was rejected by J. B. Watson and other American psychologists of the behaviorist school in the early 1900s. Consciousness was not a topic of psychological study in the United States for more than forty years. In the 1950s diverse factors emerged in American life and science that made consciousness again a significant area of research in psychology, neurobiology, and philosophy. These factors included the development of psychoactive drugs in psychiatry and in the counterculture; experiments in psychological warfare and brainwashing as a result of the Korean War and the Cold War; studies in cybernetics and artificial intelligence; and developments in brain and sleep research, as well as interest in Eastern religions (Yoga, Zen Buddhism and others). Intensive comparative and experimental research, some under secret governmental auspices, was carried on for some years, beginning in the 1950s. This included work with hallucinogens, particularly LSD-25, also sensory deprivation, biofeedback, sleep research, etc. Advances in technology, for example, the development of the electroencephalogram (EEG) and positron-emission tomography (PET), have made it possible to study some aspects of brain functioning in relation to states of consciousness. While awareness is central to most current definitions of consciousness, there is no single consensus definition of the term, nor is there agreement on methodological or theoretical approaches to the subject. With 19th-century interest in consciousness and introspection in psychology, and research in hypnosis, hysteria, and related phenomena in psychiatry, it became evident that mental processes exist of which the individual is not aware. As part of his system of psychoanalysis, Freud termed these processes unconscious concluding that most mental activity is unconscious. Material that is not currently present in awareness but can be easily recalled is conceptualized as existing on a "preconscious" level. The term unconscious has other meanings as well: it may refer to a person who has fainted, is anesthetized, or is in a coma, or one who has "lost consciousness." It is also used for automatic patterning of learned behavior, such as those in language (phonology and articulation, syntax, etc.), motor behavior (e.g., styles of walking, gesturing), or other learned skills. Most physiological processes occur below the level of conscious awareness and are "nonconscious." C. G. Jung speaks of a "collective unconscious," which is said to be inherited and shared by segments of humanity. The attribution of consciousness to inanimate matter and of humanlike consciousness to animals is referred to as anthropomorphism. Some scholars (e.g., Ornstein 1973) have distinguished two modes of consciousness, the intellectual and the intuitive. Deikman (1996) distinguishes between "instrumental" (or "object-mode") and "receptive" consciousness. Tart (1973) has proposed that ordinary consciousness is not a given but a construction, involving elements such as attention/ awareness, self-awareness (i.e., awareness of being aware), volition, energy and quantity of energy, and psychological and mental structures. Importantly, these elements are variable in time, and learning plays an important role. Ordinary waking consciousness is part of general animal and human mental activity and experience. Humans, however, are distinctive in that they are aware of being aware, a feature termed higher order consciousness by G. M. Edelman (1992). Such a level of consciousness requires the development of language and complex symbolic systems. Human consciousness as we know it is the product of the evolution of the species. In the individual, adult consciousness is the result of developmental processes, including significant cultural factors. Consciousness varies with states of maturation and is modified in abnormal and pathological conditions (mental retardation, sensory deficits, senility, etc.). It is affected by training and experience. Research has shown that several sleep and dream states exist not only in humans including neonates, but in all mammals that have been tested. The relationship between brain functions and states of consciousness, however, is a major current field for research and debate. Concepts or discussions of consciousness exist in some other cultural traditions. For example, like William James, classical Buddhism stresses that consciousness (Vijñāna) is not a substance, is in constant flux, and cannot exist independent of matter, mental processes, emotions, and perceptions. Concepts and theories of "consciousness" are generally part of a larger scheme of understanding of psychological functioning, also including concepts such as the self, ideas of individual identity, etc. In Buddhism, "consciousness" is part of a system that includes ideas of death and reincarnation, and a general universal consciousness in which the individual participates. In this system the individual is viewed as a whole, whereas in the West there is a persistent dualism, involving a mind/body split, in spite of a general rejection of such a dualism by most contemporary psychologies and philosophical systems. Dualism, however, has strongly affected theories of consciousness among philosophers. Other conceptualizations of the structure of the personality and the individual's relationship to the society and the universe also exist. For example, among the Yoruba of Nigeria, the Fon of Benin, and their descendants in the Americas, as shown in the Afro- American religions of Haiti (Bodou), Cuba (Santeria) and Brazil (Candomblé, Xango), the person has two "souls," one of which may be replaced when the individual is "possessed" by a spirit. The individual's behavior, self-presentation and identity, attitudes and sensory modalities (e.g., pain threshold) typically appear to be transformed; the state is generally followed by amnesia. For the participant, however, this is not a different state of consciousness but the displacement of the ordinary self by another personality or entity. Among the peoples of Northern Eurasia and some parts of the Americas the practice termed shamanism has been described. An important aspect of this religious and healing system of rituals is the practitioner's "spirit journey." Here, the individual, in an altered state of consciousness, experiences contact with various spirit beings, often in order to heal a patient. This state, in which the shaman may be quite insensitive to the immediate surroundings, is typically not followed by amnesia for the experience but by a report of the events of the journey. Research in hypnosis, hallucinogens, meditation, and related matters led to the identification of altered (or alternate) states of consciousness (ASCs) and with it of state- specific learning; that is, what is learned in one state of consciousness may not be accessible in another. These are states that differ in some qualitative respects, subjectively or objectively, from ordinary waking consciousness. Once systematic research in this area was undertaken, it became evident that a very large number of ASCs could be identified and classified by method of induction (Ludwig, 1972). Sleep itself involves four states or stages differentiated in EEG patterns and by subjective experience; in addition there are intermediate states between sleeping and waking. In lucid dreaming, the dreamer, while asleep, is aware of dreaming and able to manipulate or control the content of the dream. Some "altered" states are induced by changes in body chemistry whether through drugs including alcohol or tobacco, infections producing high fevers, or physiological disorders as varied as diabetic coma, epileptic auras and seizures, migraine auras, and other pathological brain states. Other types of ASCs are induced by heightened or lowered stimulation or alertness. Importantly, it came to be increasingly recognized that differences exist among various cultures in the practices associated with the intentional induction of some altered states and in the interpretation placed on particular states, and that learning plays a major role in both the objective and the subjective dimensions of states of consciousness. It has long been known that in classical antiquity epilepsy, called morbus sacer ("sacred disease") was thought to be of supernatural origins, or that during the Middle Ages in Europe certain aberrant mental states were considered to be due to diabolic possession, requiring exorcism. Indeed, beliefs in demonic possession and practices of exorcism exist today in segments of American society. Prehistoric archaeological evidence suggests that some ASCs were ritually used in Upper Paleolithic times. It has been argued that religious beliefs originated