What is the most disturbing brain mechanism that activates whenever we find ourselves in extreme conditions?

Third man syndrome is a particular psychological phenomenon in which, in the event of conditions of extreme resistance, on the verge of death, the brain sends electrical signals (called switches) such as to allude to the presence of an additional figure next to the exhausted person.

Sir Ernest Shackleton, in his book “South” described the phenomenon for the first time in 1919. He was convinced that a disembodied companion joined him and his men during the last leg of his 1914–1917 Antarctic expedition. The team was stuck in the pack ice for more than two years and endured immense hardship in their attempts to reach safety. Shackleton wrote, “during that long and torturous march of thirty-six hours over the nameless mountains and glaciers of South Georgia, it often seemed to me that there were four of us, not three.”

In recent years, well-known adventurers such as mountaineer Reinhold Messner and polar explorers Peter Hillary and Ann Bancroft have reported experiencing the phenomenon.