In Homo sapiens at least, laughter seems to be universal – wherever you go in the world, people laugh.

Laughter is a non-verbal expression of emotion. Like screaming or sobbing, it has more in common with noises made by other mammals than it does with speech.

Though many writers (including Nietzsche) have considered laughter to be unique to humans, it has actually been described in several other mammals: other primates laugh in a way we can recognise. For example chimps, like humans, laugh when they’re tickled and when they are playing.

However, the laughter of other species can be harder for us to hear because it is too high. But after lowering the pitch of rat calls, scientists observed that the animals make the same distinct chirping sound when they play with each other as they do when tickled by a researcher.

It therefore seems possible that laughter may be a more ubiquitous mammal behaviour associated with social bonding and affection, rather than with jokes. This social use of laughter is also true for humans: we laugh most when we are talking with our friends, and not – as you might think – when we hear a good joke.

Main image: Getty Images