Sleep paralysis is often accompanied by terrible hallucinations, the nature of which is not yet fully understood. Why do people most often see faceless shadows, regardless of the cultural myths that have a strong influence on these kinds of hallucinations? The most common among these are ghosts or mysterious presences, because the hallucinations are rarely visual, and when they are, they are difficult to distinguish.
Of course, there are cases of full-fledged visual hallucinations, when a person describes demons or witches in some detail. However, most of the time these are the same shadow characters that become associated with mythical creatures. Perhaps we are most afraid of what we cannot see. After all, many horror films are based on this very effect. We experience the strongest fear when peering into the darkness and picturing the worst in our imaginations.
Answering this question in a recently published article in the journal “Medical Hypotheses”, Baland Jalal of the University of Cambridge puts forward an interesting right-hemisphere hypothesis. The researcher suggests that it is the main reason for such hallucinations. Indeed, the right hemisphere is responsible for non-verbal information processing. We often hear that the left hemisphere is responsible for logical thinking, while people with a well-developed right hemisphere are imaginative, intuitive, and creative.
By comparing the different computational styles in the processing of information in the right and left hemispheres, Jalal concludes that the right hemisphere is responsible for the hallucinations associated with sleep paralysis, as well as out-of-body experiences. Moreover, the ghostly hallucinations (spirits and faceless shadows) that occur during sleep paralysis are not simply born out of the active centers of the right hemisphere. They are caused by the fact that, during the REM phase of sleep, our visual system works at reduced capacity, or in a kind of energy-saving mode.
Simply put, the load on visual information processing is minimized, which causes superficial readings of information and the refinement of unknowns using the active brain functions – so-called surface interpolation, enhanced by our imagination. That is why figures in the dark seem to us to be living characters straight out of horror films, yet in most cases, we see them as blurry and faceless. If the scientist’s hypothesis is correct, patients with injuries to the right hemisphere will be less likely to experience horror during attacks of sleep paralysis, or said attacks can be temporarily turned off using transcranial stimulation.
We are looking forward to experiments that prove this hypothesis.
The article was published in January 2021 in the journal Medical Hypotheses.
