Third man syndrome: Perceived presence during extreme survival situations

The phenomenon known as ‘third man syndrome’ involves individuals experiencing the perceived presence of another person during extreme situations involving danger, isolation, or physical exhaustion. Those affected report feeling a companion walking beside them or receiving guidance and emotional support, despite being physically alone.

The term is linked to British explorer Ernest Shackleton, who reported feeling as though a fourth person was present during an Antarctic expedition. Similar experiences have been documented among mountaineers, polar explorers, and sailors.

While the exact cause remains unknown, researchers link the phenomenon to factors such as isolation, sleep deprivation, dehydration, extreme cold, and oxygen deficiency. One hypothesis suggests it stems from alterations in how the brain, specifically the right temporoparietal zone, integrates information regarding the body and its surroundings.