Got an altitude problem?

You know that feeling you get when you're standing in a high place? The sudden urge to jump... I don't have it," Jack Sparrow, always unpredictable, says, in Pirates of the Caribbean 4: On Stranger Tides (2011).

- Anesha George

He's standing at the edge of a cliff at the time, and probably lying. Because what he's referring to is rather universal. It's called the High Place Phenomenon (HPP). In French, it is the rather lyrical L'appel du Vide, or Call of the Void.

This is the sudden inexplicable urge to veer off a bridge, lean out of a balcony, or indeed jump from a high place.

Where does it come from?