Repetition has a strange relationship with the mind. Take the experience of déjà vu, when we wrongly believe have experienced a novel situation in the past – leaving you with an spooky sense of pastness. But we have discovered that déjà vu is actually a window into the workings of our memory system.

Our research found that the phenomenon arises when the part of the brain which detects familiarity de-synchronises with reality. Déjà vu is the signal which alerts you to this weirdness: it is a type of “fact checking” for the memory system.

But repetition can do something even more uncanny and unusual. The opposite of déjà vu is “jamais vu”, when something you know to be familiar feels unreal or novel in some way.