On 20 May 1916, Ernest Shackleton, Frank Worsley, and Tom Crean reached Stromness, a whaling station on the north coast of South Georgia. They had been walking for 36 hours, in life-threatening conditions, in an attempt to reach help for the rest of their party: three of their crew were stuck on the south side of the island, with the remainder stranded on Elephant Island. To reach the whaling station, the three men had to cross the island’s mountainous interior with just a rope and an axe, in a journey that few had attempted before or since. By reaching Stromness they managed to save all the men left from the ill-fated Imperial Transantarctic Expedition.

They did not talk about it at the time, but weeks later all three men reported an uncanny experience during their trek: a feeling that “often there were four, not three” men on their journey. The “fourth” that accompanied them had the silent presence of a real person, someone walking with them by their side, as far as the whaling station but no further. Shackleton was apparently deeply affected by the experience, but would say little about it in subsequent years, considering it something “which can never be spoken of”.

Encounters such as these are common in extreme survival situations: guardian angels, guides, or even Christ-like figures have often been reported. We know them now as “third man” experiences, following a line in TS Eliot’s poem, The Wasteland:

“Who is the third who walks always beside you? When I count, there are only you and I together. But when I look ahead up the white road, there is always another one walking beside you”

Eliot had heard of Shackleton’s encounter, but could not remember the precise details – meaning that the “fourth” man became the “third”.

In his book The Third Man Factor, John Geiger collects together a wide range of third man stories, including accounts from mountaineers, sailors, and survivors of terrorist attacks. They all involve a strong impression of a felt presence, sometimes with a voice or a shadow-like image, but often without a clear form. Extreme physical conditions, threat to life, and social isolation all seem to trigger the feeling of a presence, which will often feel as if it has a spiritual or guiding purpose.

In the case of the third man, it is tempting to think that strong feelings of presence act as some sort of hallucinatory defence mechanism – something that could happen to anyone, but only in very extreme scenarios. Such experiences are, however, also reported in much less dramatic circumstances. Following bereavement, for example, many people report sensing the presence of their deceased loved one; a feeling that someone is still in the house, just upstairs, or in their favourite chair.

Felt presences are common during the experience of sleep paralysis, when people have the feeling of being awake but not being able to move their body. Often this is accompanied by a sense of a presence in the room, along with physical sensations such as pressure on the chest and difficulty breathing. Feelings of presence also feature in particular neurological disorders – such as Parkinson’s disease – and cases of brain damage.

The different contexts in which felt presences occur give us some clues about what might be happening. For example, their association with bereavement suggests that emotional factors (eg, strong, persistent feelings of sadness), as well as strong expectations that another person ‘should’ be present, are important factors. In the case of Parkinson’s disease, they appear to occur most often in people who receive high doses of medication, suggesting that the neurotransmitter dopamine may well be involved in felt presence experiences.

Perhaps most revealingly, people with brain injuries who report felt presence experiences often have damage to an area called the temporoparietal junction (TPJ), and electrical stimulation of this area can induce the feeling of a nearby sensed presence. Among many other things, the TPJ appears to play an important role in maintaining an internal representation of our body image. So, one possibility is that feelings of a presence occur when our representation of our body is somehow duplicated or projected outside of us (something known as an “autoscopic” experience). Supporting this idea, often the person having a felt presence feels like they have some important bond or affinity with the figure they experience.

On the other hand, some feelings of presence are described as being very alien and often malevolent towards the perceiver: sleep paralysis, for example, is often accompanied by feelings of anxiety and dread in relation to the “entity” in the room. It has been argued that cases of sleep paralysis also involve old, evolutionary impulses to detect threat in our environment. This, coupled with muscle paralysis, could lead to an intense fear of the presence in the room.

Understanding more about how and why felt presences occur has the potential to tell us many things about ourselves: how we react under intense mental or physical stress, how we deal with danger and threat, and how we recognise the shape and position of our own body. But one thing it also may do is shed light on other unusual experiences that are hard to understand.

For example, in cases of hearing voices (sometimes called auditory verbal hallucinations), people sometimes struggle to describe the nature of the “voice” they hear. Because we tend to use the term ‘hearing voices’ to describe this experience, researchers and clinicians often focus on auditory characteristics (Did the voice sound like it was coming from inside your head, or outside of your head? How loud was the voice?). But sometimes, feelings of presence might accompany the voice-hearing experience, and some people who hear voices describe their “voice” being there even when it is not speaking; a voice that seems to have a presence of its own. In these cases, hearing a voice may be much more like sensing a person or being visited by an entity, rather than experiencing sound. Interestingly, there is also some evidence that the neural connectivity of the TPJ area is organised in a different way for people who hear regularly hear voices.

If voices and presences were to overlap in some way then it could have consequences both for research and treatment, when help is sought. For instance, researchers might need to look closer at social factors that seem to trigger voices, or study brain networks that support social cognition and body representation. Approaches that involve interacting with voices and treating them like people – something that voice-hearers themselves have often advocated – could prove to be useful for health professionals, and some psychologists are already having success with such techniques. In this way, the third man does not just tell us about our own minds or bodies; it offers us a way to help and understand others – just as he did for Shackleton.

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