The August edition of The Psychologist has a fascinating article on the awareness during sleep paralysis, a state where we wake but can’t move and sometimes experience intense hallucinations.
This form of awake sleep paralysis is remarkably common and has been explained throughout the world with a diverse and colourful range of cultural explanations.
In Newfoundland it’s called the ‘old hag’, in Hong Kong ‘ghost oppression’, in Japan ‘kanashibari’ – the result of magic from a Buddhist spirit and famously, in Europe of the middle ages, the effect of the succubus demon. A recent study looked at the phenomenon among Mexican teens and found it was explained as ‘a dead body climbed on top of me’.
The article also tackles science of this curious state and one of the most interesting bits is where it discusses the evidence for sleep paralysis being the intrusion of the rapid eye-movement (REM) stage of sleep into wakefulness.
It turns out that there are some people who experience REM almost immediately after falling asleep and they are much more likely to experience awareness during sleep paralysis:
This research strongly suggests that sleep paralysis is related to REM sleep, and in particular REM sleep that occurs at sleep onset. Shiftwork, jetlag, irregular sleep habits, overtiredness and sleep deprivation are all considered to be predisposing factors to sleep paralysis (American Sleep Disorders Association, 1997); this may be because such events disrupt the sleep‚Äìwake cycle, which can then cause SOREMPs [sleep-onset REM periods].
Of course, episodes of sleep paralysis occurring as people emerge from sleep cannot be explained in terms of SOREMPs, but it seems reasonable to argue that such episodes may well involve a similar state of consciousness, mixing aspects of both normal wakeful consciousness and REM consciousness. Needless to say, for practical reasons such episodes are inherently more difficult to study in psychophysiological terms as there is currently no known way to induce their occurrence.
Link to The Psychologist article ‘Terror in the night’.
Full disclosure: I’m an occasional columnist and unpaid associate editor of The Psychologist. I have experienced sleep paralysis once and interpreted it as sleep paralysis.