This week’s New Scientist has a fascinating article about recent research into the cognitive origins of that most unsettling of phenomena, déjà vu:
Déjà vu can happen to anyone, and anyone who has had it will recognise the description immediately. It is more than just a sense that you have seen or done something before; it is a startling, inappropriate and often disturbing sense that history is repeating, and impossibly so. You can’t place where the earlier encounter happened, and it can feel like a premonition or a dream. Subjective, strange and fleeting, not to mention tainted by paranormal explanations, the phenomenon has been a difficult and unpopular one to study.
“Speculations about past lives or telepathy aside, the first biological explanations of déjà vu were based on ideas that two sensory signals in the brain – perhaps one from each eye or each hemisphere of the brain – for some reason move out of sync, so that people have the experience of reliving the same event. “Mental diplopia”, as it was called, is intuitively appealing but the evidence is stacked against it … Now another theory is gaining credibility. Perhaps déjà vu feels like reliving a past experience because we actually are – at least to some extent …”