Laughter is a strong, positive vocal expression of emotion, which is found throughout human cultures and also in many mammals. Although you might think of laughter as something people do when they hear jokes, in fact we laugh most often when we are talking with our friends. Indeed, for both rats and humans, laughter first appears in babies when they interact with their caregivers.
Laughter is a social emotion, and it is physically contagious.
This can be detected in people's brains when they listen to
laughter. Scientists have found that the brains of people who are
good at distinguishing different kinds of laughs show a greater
tendency to join in with the laughter they hear.
How it works
It is only relatively recently that scientists have started to
investigate positive emotions like amusement and joy. They have
found that there is good cross-cultural recognition of laughter -
wherever you go in the world, people know what laughter means.
Scientists have also found a neural signature for laughter -
when you hear a laugh you activate the same brain regions that you
would use to move your own face into a smile. These 'mirror'
responses to laughter reflect the fact that when we hear someone
laugh, we are primed to join in (even during a brain scan, which is
not very amusing!).
Laughter has been described as 'the shortest distance between
two people' (Victor Borge) but it's also the case that we use
laughter to shorten these distances. Laughter is social glue that
makes and strengthens our links with other people