The out-of-body experience (OBE) is one in which the "centre of consciousness" of a person appears, from the viewpoint of that person, to occupy temporarily a position which is spatially remote from his or her physical body (9, see also 1,10,12). The definition refers to an experience rather than to an actual event, whether accurately described or not. the term "centre of consciousness" does not assume any particular theory or content of the imagery. In occult traditions, a deliberate induction of an OBE is termed astral projection. The term OBEr refers to a person who has experienced an OBE. Research interest has recently accelerated in tandem with interest in its "cousin" the near-death experience (NDE).

Knowledge about the OBE comes from three sources. First, people's descriptions of their OBEs have been compiled into case collections (5,15) and questionnaire surveys (2,4,6,8).

Second, people who can deliberately induce an OBE have written books of instruction and self-observation (14). A problem with these methods is that human testimony is fallible, and that spectacular OBEs are over-represented as they are remembered better. Such data serve only as sources of hypotheses. Third, procedures for inducing OBEs in the laboratory permit controlled investigation. However, experimental OBEs tend to be more vague than real-life spontaneous ones (4). The subject is under pressure to produce an OBE. Induction methods (particularly hypnotic) are susceptible to contamination from the bias (beliefs) of the experimenter.

Irwin summarises 37 studies of the incidence of OBEs (9). In four samples of the general population, the average incidence was 10%. In 12 samples of university students, the average was 20% (more willing reporters? greater drug use?) In nine samples of first year psychology students from the University of New England, Armidale NSW, the average was 30%. Irwin finds no correlation of OBEs with age, sex marital status, education level, social class, religious beliefs, race, brain physiology, and prior knowledge of OBEs. Nor are OBEs indicators of mental illness (4A,6,9).

Characteristics

In most spontaneous OBEs, the person suddenly becomes aware of being outside his or her physical body. This "self", apparently located above the body, perceives a vivid "real" impression of the nearby environment. The OBEr reports looking down, usually for periods up to five minutes, and seeing his or her own physical body. Some OBErs describe their "self" as a specific shape, usually a replica of the current physical body, although some elderly persons report a younger OBE body. Rarely, a point of light or a mist is reported, or no shape at all ("asomatic"), but even here a shape is implied because the subject may report squeezing through a space.

The "centre of consciousness" of a person appears, from the viewpoint of that person, to occupy a position spatially remote from [the] physical body.

About 20-30% of OBEs, particularly those under the control of the subject, involve distinctive skeleto-muscular sensations at the beginning and/or end of the experience. These include percussive noises (buzzes, clicks), vibrations in the body, catalepsy and/or momentary blackouts. Some OBEs contain extrasensory elements such as an ESP experience (9,10).

More than 90% of OBEs are naturalistic and visual (i.e., the external world is seen more or less as it really is). Most features of a room are seen correctly, except that a door, for example, may appear open when it is actually closed. Rarely, odd effects occur, such as time distortion, wide-angle vision and seeing through objects. A few visual OBEs are also auditory; vision and sound are not sensed separately, but in a single comprehensive way ("synthetic"). A few OBEs are sensory; there is only an intuitive conviction that the "centre of consciousness" is external to the body.

A few OBEs reflect an exotic world, such as the person moves through a dark tunnel towards a golden light and peace ("paradise"), populated by "spirits" of the dead (similar to some NDE reports). The medium Helene Smith claimed she took out-of-body trips to the planet Mars. In early spiritualist literature, in particular, an "astral cord" is reported, connecting the physical body and OB body; if the cord breaks, the subject will die. Such exotic features are probably determined by the culture and beliefs of the subject (9,10).

The OBE may happen spontaneously, or it may be forced, for example, by means of drugs (hallucinogenic or anaesthetic), hypnosis or emotional trauma. Rarely, a person (often a meditator) can produce an OBE at will. The OBEr displays less fear of death. The OBEr sees with strikingly increased clarity, vividness and awareness of "self", relative to normal consciousness within the physical body. In long-duration OBEs, it is possible to control the content, location and termination of OBEs by directing attention to the required state of affairs.

OBErs also tend to report more falling dreams, lucid dreams and mystical experiences than non-OBErs. OBErs are more likely to be fantasisers or "fantasy-prone" people (18). Unlike normal and lucid dreams, there are no rapid-eye movements during OBEs. In apparitions and autoscopic images of oneself, the "centre of consciousness" is still within the physical body. In depersonalised images of oneself, caused by fear of impending death, the depersonalised self feels like being a stranger to the physical body; in contrast, the OBEr feels "more real". In schizophrenic body boundary disturbances (unlike OBErs), the person cannot distinguish between the real and imagined world.

The OBE is only one element of the NDE: about 10% of OBEs are reported in conjunction with NDEs (6,9).

OBErs are more likely to be fantasisers than persons not having OBEs.

A person reporting spontaneous OBEs has more mystical experiences, compared to non-OBErs (2,4). OBEs happen in two contrasting contexts.

Low arousal of the brain. The person is very relaxed (mentally and physically) - on the point of going to sleep or waking up, or meditating, or in a very quiet setting. If the person is active at all the activity is automatic, such as walking, jogging, or a skilled musician playing a familiar composition. Most OBEs probably occur when waking up (the hypnopompic state).

High arousal of the brain. About 30% of OBEs. Associated with elation, euphoria (such as fast driving, listening to loud music), intense anger, confrontation with death, and sexual orgasm.

Compared to non-OBErs, subjects who can produce deliberate (experimental) OBEs are better at the ability to control the content of, and stop, dreams (4). Most programs for deliberate induction (8) emphasise physical and mental relaxation in a quiet environment; creating mental imagery (for example, of a specific symbol, or of the impression of leaving the body); and total but effortless absorption in these thoughts. Hypnosis and sensory deprivation are useful. Glaskin, an Australian novelist, has made popular the Christos technique of J & N.Parkhurst, involving simultaneous massage of forehead and feet (7).

Induction methods interact with an expectation or need, or motivation, that an OBE will occur. Taking drugs is not recommended, because of the relative lack of control over the OBE.

The external world seen from the out-of-body state is a memory of the real world.

Mind-body separation?

Separation theories propose that the OBE is literally as it seems to be, that is, a spatial separation of mind/spirit from the physical body. Because the OBE is so real and vivid, it is not surprising that this theory has support. The concept of a physical double is supported by Crookall, Whiteman, and by some theosophists (e.g., Besant and Powell) and spiritualists (such as Findlay). But no one has convincingly suggested what such a body is made from. The idea that a non-physical double ("soul") leaves the physical body is more popular (9).

These models trend to provide post-hoc explanations of OBE features. Moreover, scientific tests have been inconclusive or ambiguous. For example, if an out-of-body state is sent to a distant locality, one cannot be certain that the data was not got by clairvoyance, or from forgotten prior knowledge of the locality.

A subject, Miss Z, tested by Tart, was able to correctly read a 5-digit number on a shelf five feet above the bed where she slept. Because Z was not always watched, the possibility she peeked cannot be excluded.

Keith Harary attempted experimentally to influence human and animals during his out-of-body state. Humans, rodents and snake showed no effects compared to non-OBE periods; but a kitten was quieter and less active during out-of-body periods, although it did not obviously look at the supposed locality of the out-of-body image (13).

The neutral term "imagery" is preferred to "hallucination" - a term that originally implied mental illness. Imagery theories assert that the OBE is a state of consciousness characterised by "dissociative" imagery (16A). The external world seen from the out-of-body state is a memory of the real world. This explains OBEs in which the OBEr sees the real world correctly, except for a few misremembered bits. It also explains exotic misperceptions as the product of the OBErs beliefs and culture. The imagery may also incorporate apparently extrasensory information about discrete events.

Attention and absorption

Imagery theories can be evaluated in relation to a psychological process called attention - the selection of some items to enter consciousness while other items remain excluded.

The ease of having an OBE is related to the ease of entering meditative and hypnotic states, and with having lucid dreams and mystical experiences. The common factor in all of these is absorption - the (attentive) ability or capacity of the person to focus on the mental task at hand to the exclusion of all other disturbances (9). This capacity applies to the person, and not just to the induction phase. All body activities (termed somatic or kinaesthetic) cease or become automatic, so that no more attention is paid to them. This is similar to the "onepointedness" of meditators, in which attention is focussed on some event such as chanting a repetitive mantra. The return of attention to body processes ends the OBE.

OBErs also have a need for (as well as a capacity for) absorption. Irwin relates this need to a concern for, and attention to, one's mental processes. A psychoanalytic model, based on narcissism, proposes that the OBEr needs to step outside his or her body to look at it as others do. However data shows that OBErs are not excessively obsessed by their physical appearance. Ehrenwald states that the OBEr has a need to convince oneself of immortality by observing the "soul" leave the body. This idea is also not supported by data: "supernatural" OBEs do not happen most often to religious people (10).

In particular, OBErs tend to evoke a type of absorption that Irwin calls cross-modal experiencing or synaesthesia (9); one sensory mode (e.g., visual) tends to evoke imagery in another mode such as auditory. This occurs especially for persons reporting an "astral body" or terminal sensations.

OBErs do not have exceptional ability or skill to generate and control and manipulate general visual images. However, Irwin found that the ability to generate body-like OBEs is related to the extent the subject can control the OBE. Nor does the tendency to have an OBE depend on the vividness of the imagery nor on the person being a visualiser rather than a verbaliser. However, OBErs may be better at judging how an object appears from different perspectives (9).

Blackmore considers that an OBE is an altered state of consciousness produced when the body is deprived of sensory input, as during meditation or stress, disrupting the normal "reality model" in favour of an OBE reality model built from imagery and memory (3).

Palmer supposes that euphoria or relaxation produces a decline in skeleto-muscular stimulation and this lack of body-sense feedback may threaten the subjects sense of self (16). The OBE, which mainly occurs in the hypnopompic (waking up) state, is an attempt to restore self-concept, and to save the ego from being destroyed. This model fits spontaneous OBEs best.

Irwin argues similarly that OBEs involve losing touch with body senses, as a result of becoming absorbed: extremely low or high arousal of the brain interacts with a capacity (and need) for the individual to have OBEs. This removes the conditioned preconscious (momentarily out of awareness) assumption that "I" must be in the physical body. The static body image is transformed into a conscious, active, disembodied body image that incorporates synesthetic (visual plus auditory) experiencing of this new image (9, 10).