Why do we hiccup?

Nobody knows, which is remarkable for something universal, harmless and instantly recognisable. A hiccup is a sudden involuntary contraction of the diaphragm followed about 35 milliseconds later by the vocal cords snapping shut - and that second part is the puzzle, because it makes the reflex useless as breathing.

The best-known idea traces it to our ancestry. Animals that breathe with both gills and lungs, like tadpoles, use a very similar motion to push water across the gills while keeping it out of the lungs, and the neural circuitry may simply have been retained. Another suggestion is that it helps a nursing infant clear air from the stomach, which fits the fact that fetuses hiccup in the womb from about the second trimester and premature babies do it a great deal.

Most remedies work, if they work, by raising carbon dioxide or by stimulating the vagus nerve - which is the honest version of holding your breath, drinking from the far side of a glass, or being frightened. The record holder, Charles Osborne, hiccupped continuously for 68 years.