"What is the physiology of OBEs?"


Clearly there are similarities between OBEs and dreams. In both we experience a world in which imagination plays a great part and we can perform feats not possible in everyday life. But the OBE differs in many important and obvious ways from what we have called an ordinary dream. For a start, it usually occurs when the subject is awake, or at least if drowsy or drugged, not sleeping. Second, the imagery and activities of an OBE are usually much less bizarre and more coherent than those of an ordinary dream, and most often the scenery is something from the normal environment rather than the peculiar setting of dreams. Third, OBEers are often adamant that their experience was nothing like a dream. Finally, there is the great difference in the state of consciousness. Ordinary dreams are characterized by very cloudly consciousness at best, and are only recognized as dreams on waking up.

But these differences are not enough. You may argue that in a lucid dream both the imagery and the state of consciousness are much more like those in an OBE. So perhaps the OBE is a kind of lucid dream occurring in the midst of waking life. One way to find out might be to determine the physiological state in which the OBE takes place. Such a finding can only be made by means of laboratory experiment; but first we need to catch an OBE in the laboratory.

Observing an OBE in the laboratory setting is not easy. Most people who have an OBE have only one, or at most few, in a lifetime. Capturing an OBE requires a special kind of subject, one who is both able to induce an OBE at will, and willing to be subjected to the stress of being tested. Fortunately there are such subjects.

One of the first to be tested was a young girl called Miss Z., by Charles Tart who studied her OBEs [Tar68]. Her OBEs all occurred at night. She used to wake up in the night and find herself floating near the ceiling. With Miss Z. as subject Tart initially wanted to test two aspects of the OBE: first, whether ESP could occur during an OBE, and second what physiological state was associated with the experience. Altogether, Miss Z. spent four non-consecutive nights sleeping at the lab.

During her first night Miss Z. had no OBEs. During the second night she woke twice and reported that she had been floating above her body. During the first experience Miss Z. had not yet fallen asleep when the OBE occurred, and the EEG showed a drowsy waking pattern followed by waking when she told Tart about the experience. All the time the heart rate had been steady and there were no REMs. Then at 3.15 a.m. Miss Z. woke up and called out 'write down 3.13.' Apparently she had left her body and lifted up high enough to see the clock on the wall. At that time the EEG showed various patterns but predominantly theta and alphoid activity. There were few sleep spindles (a feature of the EEG pattern in certain stages of sleep), no REMs, no GSRs (galvanic skin response) and a steady heartbeat.

On the third night Miss Z. had a dramatic OBE. She seemed to be flying, and found herself at her home in Southern California, with her sister. Her sister got up from the rocking chair where she had been sitting and the two of them communicated without speaking. After a while they both walked into the bedroom and saw the sister's body lying in bed asleep. Almost as soon as she realized that it was time to go, the OBE was over and Miss Z. found herself back in the laboratory. Tart was not able to contact the sister to check whether she had been aware of the visit, but the physiological record showed that there was mostly alphoid activity with no REMs and only a couple of minutes of Stage 1, dreaming sleep, with REMs.

The last night was in some ways the most exciting, for on that occasion the subject was able to see an ESP target provided; but the EEG record was obscured by a lot of interference. Tart described it as somewhat like Stage 1 with REMs, but he added that he could not be sure whether it was a Stage1 or a waking pattern.

Amongst all these confusing and changeable patterns, some certainty does emerge. In general the EEG showed a pattern most like poorly developed Stage 1 mixed with brief periods of wakefulness. For this subject at least OBEs do not occur in the same state as dreaming. Tart would have liked to have continued working with Miss Z. but this proved impossible as she had to return to Southern California.

However, Tart [Tar67] was able to work with another subject, Robert Monroe, well known from his books. Monroe was monitored for nine sessions with EEG and other devices. In this environment Monroe had difficulty inducing an OBE. Electrodes were clipped to his ear, and he found them very uncomfortable. During all the time that he was trying to have an OBE his EEG showed a strange mixture of patterns. There was unusually varied alpha rhythm, variable sleep spindles, and high voltage theta waves. On the whole Tart concluded that Monroe was in Stages 1 and 2 and was relaxed and drowsy, falling in and out of sleep. His sleep pattern was quite normal and he had normal dream periods and sleep cycle.

During the penultimate session Monroe managed to have an OBE. Tart concluded that Monroe's OBEs occurred in the dreaming state; but this idea presented him with a problem. Monroe claims that for him, dreaming and OBEs are entirely different. Tart finally concluded that perhaps the OBEs were a mixture of dreams and 'something else.' This 'something else' might, he thought, be ESP.

One of the next subjects to be tested in this way was Ingo Swann. In several experiments at the ASPR [OM77] Swann was attached to the EEG equipment while he sat in a darkened room and tried to exteriorise, in his own time, and to travel to a distant room where ESP targets were set up. He did not fall asleep and was thus able to make comments about how he was getting on. After some months of this type of experiment Swann suggested that he might be able to leave his body on command and so he was arranged to receive an audible signal to tell him when to go, and when to return. Apparently he succeeded in this effort, which meant that OBE and other times could easily be determined and compared.

During the OBE periods, the EEG was markedly flattened and there were frequency changes, with a decrease in alpha and increase in beta activity. While these changes took place, the heart rate stayed normal. These findings are rather different from those with previous subjects in that Swann seemed to be more alert during his OBEs. Perhaps this just confirms what was learned from case studies, that the OBE can occur in a variety of states. But perhaps most important is that in no case so far did there seem to be a discrete state in which the OBE took place. There were no sudden changes in either EEG or autonomic functions to mark the beginning or end of the OBE. Any changes were gradual; unlike dreaming, the OBE does not seem to be associated with a discrete physiological state.

The one other subject who has taken part in a large number of OBE experiments is Keith ('Blue') Harary. The experiments in which his physiological state was measured were carried out at the Physical Research Foundation [Mor73, HJH74, JHHLM74, MHJHR78]. The findings were different again from those of previous studies. Here there were no changes in EEG. The amount and frequency of alpha were the same in OBE and 'cool down' periods and there were only slightly fewer eye movements in the OBE phases. These measurements alone show that Harary was awake and that his OBEs did not occur in a sleeping, dreaming or borderline state.

Other measures did show a change. Skin potential fell, indicating greater relaxation, and it was this measure which provided the best indicator that an OBE had begun. Both heart rate and respiration increased. These changes are surprising because they imply a greater degree of arousal; the opposite of the finding from skin potential. So in some ways Harary was more relaxed, but he was also more alert.

Great differences between subjects tend to obscure any clear pattern in the states, but in all this confusion it is clear that the start of an OBE does not coincide with any abrupt physiological change. There is no discrete OBE state. The OBE does not, at least for these subjects, and under these conditions, occur in a state resembling dreaming. The subjects were relaxed, and even drowsy or lightly asleep, but they were not dreaming when they had their OBEs.


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