Those who have had the misfortune of experiencing sleep paralysis; a common condition where your brain becomes conscious after sleep while the rest of your body stays paralysed (BBC, 2023a), may have had the sense that someone non-existent was in the room with them. This strange phenomenon is known in the scientific literature as ‘felt-presence’; an experience of feeling that someone else is in the room with you even though there is no concrete evidence of them being there (BBC, 2023b). Those who have experienced sleep paralysis are not the only ones who have had felt-presence, however. Individuals with conditions such as psychosis, Parkinson’s, epilepsy, and brain tumours have also reported felt-presence at some point. People who take certain psychoactive substances, have certain spiritual/religious beliefs, or experience extreme stress or bereavement have also experienced it.

Research has been growing around this subject to understand why it happens, and a recent literature review by Barnby and colleagues (2023) has offered an overview of the evidence base. The review summarises what we know so far about felt-presence, but also highlights areas that require more investigation.

Methods

Barnby and colleagues (2023) carried out a literature review to collect relevant research papers about felt-presence and summarise it. They searched through PubMed and Google Scholar using relevant keywords such as “felt presence”, “sensed presence”, “extracampine hallucination”, “non-clinical voice hearers” and “heautoscopy” to narrow down to papers that explored experiences of felt-presence. They also included keywords such as “brain lesion”, “epilepsy” and “psychosis” to find papers that looked at episodes of felt-presence in certain clinical populations. This is a literature review not a systematic review, so they didn’t follow a systematic and comprehensive approach to searching and instead focused on key papers that were either known to the researchers or were included in the reference lists of these key papers. Most of the included literature was written in English, though there were a few exceptions at the discretion of the researchers.

Results

This review breaks down the current research into three categories: the philosophy and phenomenology of felt-presence, clinical and non-clinical correlates, and theoretical models and mechanisms. According to the researchers, studies on the experience of felt-presence show how there is not one common way that it is experienced; different people experience it in different ways. Measures that have been used to collect a person’s episode of felt-presence tend to measure it across two dimensions: the identity of the felt-presence and its location. However, experiences of felt-presence can vary over time. You can’t be confident that a measure taken at one point in time will represent the experience at another.

The research summarised in this review explored how different clinical and non-clinical groups appear to be more susceptible to experiencing felt-presence. It appears to be common in those with psychosis as well as other conditions that affect the brain, such as Parkinson’s, epilepsy, and brain tumours. Still, it is also relatively prevalent in non-clinical groups such as those who take psychoactive drugs, particularly ayahuasca, and people experiencing bereavement of a loved one.

Current theories on how felt-presence takes place usually involve neuropsychological models, which have highlighted the potential involvement of the temporoparietal junction, insula, and frontoparietal cortex as these are involved in related systems such as multisensory integration, body processing, and distinguishing between the self and others. The researchers highlighted how the evidence appears to support the idea that felt-presence comes from a malfunction in the brain’s ability to know where your body ends, and another begins. The idea is that conditions or experiences that impact these brain areas may induce an episode of felt-presence. A study in the review supported this idea by using electric stimulation in these brain regions to increase the chance of experiencing felt-presence. Studies that have explored the impact of psychoactive drugs also appear to show how felt-presence arises from the disruption of your brain’s ability to distinguish yourself from others.

Conclusions

Barnby and colleagues (2023) concluded that, while we are developing a good understanding of felt-presence from research, there are still a lot of gaps that require further exploration. It seems likely that felt-presence is due to something disturbing usual brain processing, but we are still missing a comprehensive theoretical framework to fully explain the exact processes involved. In other words, research is still in its early days. Despite this, we still know that this experience is quite common, particularly in certain clinical groups.

Strengths and limitations

The review gives a good overview of the key research into felt-presence, which is important for a topic that doesn’t yet have a large body of studies. The authors of this paper are experts in felt-presence, so it’s likely that they are aware of the key papers currently available in the literature. They also searched two large research databases across a long time range, to improve chances of finding other relevant papers. The search terms used seem appropriate for felt-presence, which also would have helped to uncover as many suitable papers as possible.

The main drawback to this research paper is that the authors didn’t use a systematic approach to the review. While they stated the search terms and time period they used, they didn’t mention the inclusion or exclusion criterion used to select papers for the review. This means it is very difficult to replicate this review independently to test whether its findings are reliable. The authors also didn’t fully outline the question that they were aiming to answer in this paper. Were they looking to just give a brief overview of the literature or were they hoping to highlight the limitations of the current research? Or did they want to do both? It is very hard to know for sure the main aims of the paper when it is not clearly stated.

A benefit of systematic reviews is that there is an expectation to include a quality assessment of the studies that have been included (Siddaway, Wood & Hedges, 2019). This unfortunately didn’t seem to take place for the review in question, so we do not have an objective measure of how valid and reliable the findings from the included studies are. Providing the reader with a measure of quality is very important to help them know how strong the evidence is for the conclusions made in the review. The impression I get is that the researchers used their discretion to decide which studies would be included. This opens up the potential for biases towards, or against, particular studies. The researchers were right to highlight one bias, that most studies included were written in English. However, what about other potential biases? How do we know that the authors didn’t predominantly choose studies written by researchers they have personal or professional relationships with, over researchers they were less aware of? What if studies used low-quality methods, making their results less valid or reliable? A systematic review is designed to address these concerns, and so this approach would have been preferred compared to what Barnby & colleagues (2023) decided on.

Implications for practice

Although there are some drawbacks to this review because of the lack of a systematic approach, the paper has really highlighted how common felt-presence is, as well as which groups are more likely to experience it. Several clinical client groups often seem to get the feeling that someone else is in the room with them, despite any evidence of this being the case. This can be very frightening, especially alongside other symptoms they might be experiencing. A person dealing with psychosis could have distressing auditory hallucinations alongside felt-presence, which only adds to their overall suffering. This review has highlighted how clinicians should consider asking their patients whether they have experienced any felt-presence so that they can help normalise it as well as work with the client to find ways to ease any negative effects from it.

The review has also clearly outlined several avenues for future research. For example, it seems that there is currently no psychometric measure dedicated to felt-presence, which would be handy so that we could better understand a person’s experience of this phenomenon. It could then be compared with others across the population to examine whether someone’s experience is more intense or frequent than average. It is also clear that we need a comprehensive framework to understand why felt-presence is experienced. A few studies that the review highlighted have explored some of the neuropsychological literature to address this, but more research is needed to develop robust theories.

One of the most important outcomes of this review is that felt-presence is a normal variation of human experience. Most people can encounter it in the right circumstances, whether that be from an episode of sleep paralysis or losing someone very close to them. If you ever get the feeling that you’re not alone in an otherwise empty room, don’t worry too much about telling your family, friends, or healthcare professionals. You’ll be surprised by how many other people have gone through this experience too!

Statement of interest

No interests stated.

Links

Primary paper

Barnby, J. M., Park, S., Baxter, T., Rosen, C., Brugger, P., & Alderson-Day, B. (2023). The felt-presence experience: From cognition to the clinic. The Lancet Psychiatry, 10(5), 352–362. https://doi.org/10.1016/S2215-0366(23)00034-2

Other references

BBC (2023a). Why some people wake up unable to move. Retrieved 12 November 2023, from https://www.bbc.com/future/article/20230420-the-nightmares-that-paralyse-you-in-your-sleep

BBC (2023b). ‘Felt presence’: Why we sometimes feel invisible others. Retrieved 12 November 2023, from https://www.bbc.com/future/article/20230526-felt-presence-why-we-sometimes-feel-invisible-others

Siddaway, A. P., Wood, A. M., & Hedges, L. V. (2019). How to Do a Systematic Review: A Best Practice Guide for Conducting and Reporting Narrative Reviews, Meta-Analyses, and Meta-Syntheses. Annual Review of Psychology, 70(1), 747–770. https://doi.org/10.1146/annurev-psych-010418-102803

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