Sometimes referred to as "astral projection" in esoteric literature, out-of-body experience ("OBE" or "OOBE") is a more neutral term to describe the sensation of feeling as if consciousness, or the self, is located somewhere other than where the body is physically located.

Some psychologists tend to view OBEs as simply a form of hallucination. For example, British psychologist Susan Blackmore refers to it as a particular "cognitive map," an alternative mental model, in which the mind acts as if it were experiencing the world not from the usual perspective -- that of the body -- but from some other location. In line with this interpretation, considerable work has been undertaken to explore whether people having OBEs have any particular psychological characteristics that would account for such hallucinatory experiences.

On the other hand, there are some scientific experiments in which the person having the out-of-body experience seems to actually perceive distant events or targets, as if their consciousness is truly located in that distant location. 

An intermediate position between the two extreme interpretations - true relocalization of the mind vs. mere hallucination - is that the OBE is a particularly powerful altered state of consciousness which both induces a subjective impression of mind-body separation, and greatly enhances the person's clairvoyant psi capacities. Experiments such as Tart's were not designed to distinguish between this hypothesis and the «projection» idea, but other studies have attempted to address this distinction. 

In the mid-1970s, Dr. Robert Morris and his colleagues conducted an interesting experiment with psi researcher Keith Harary as subject. Like Miss Z, Harary - at the time a psychology student - seemed able to voluntarily induce an OBE. His kitten, enclosed in a cage and constantly filmed, was to act as a biological detector of Harary, who would attempt to 'project' his consciousness into the cage from a distant room. Indeed, it was found that the kitten's agitation - its movements in the cage - was significantly reduced specifically at the moments at which Harary had been instructed to project his consciousness into the cage. Over time, however, the kitten's "baseline agitation" decreased, and its reactions to Keith Harary seem to have declined - perhaps as it became habituated to the experimental conditions (i.e., being locked in a cage!)

Of course, just as Tart's experiment could be interpreted in terms of ESP, so too the early results of this study could be interpreted in terms of mundane psi: perhaps Harary simply entered a mental state in which he exerted a calming influence upon his cat, i.e., through a form of bio-psychokinesis. A more stringent test would be for the person having the OBE to both report distant events, and to be "detected" at the distant location.

The late Karlis Osis, of the American Society for Psychical Research, sought to determine whether a physical instrument could detect a psychic's "astral body" at the time he was attempting to view a hidden target through his astral vision. Osis installed a strain gauge (which detects extremely subtle physical movements) in front of an optical device in which a graphic "target" was concealed. The setup was such that the image could only be perceived face-on - from the place where the strain-gauge was located; otherwise, from a different angle, a viewer would only see overlapping lines. The psychic Alex Tannous, who was not told about the strain gauge, was asked to attempt to project in front of the optical apparatus, and describe what he saw. Osis found that the strain gauge registered significantly more movement in those trials in which Tannous gave correct descriptions of the target. The implication may be that some facet of Tannous' mind was indeed "projecting" in front of the optical apparatus.

It is still possible to entertain the idea that in such experiments there is no true "projection," but rather a combination of successful ESP trials and unintentional PK activity. The ideal experiment for astral projection would probably necessitate not just ESP tasks and mechanical or biological detectors, but also several human observers who could independently attest to the presence of the subject's "astral body" at the moment at which projection is being attempted.

In the meantime, as suggested by psi researcher Carlos Alvarado, a primary objective would be to pay much more attention to the phenomenology of the OBE, as described by those who actually have these experiences; we may discover that terms like OBE or astral projection cover a wide range of different phenomena, and that no single explanation can account for them all.