Laughter is a funny sort of noise. The repetitive contractions give it its unmistakable rhythm, and the pressure generated by this movement leads to high-pitched squeaks and whistles. When James Naughtie mispronounced Jeremy Hunt’s name on live radio a few years ago, he managed to keep speaking ‒ he sounded as if he was in a fight with a deadly but silent assassin. For reasons we still do not understand, in a battle between breathing, speaking and laughing, laughter always wins.
One study found that laughs occur around six times per ten minutes of conversation, which may not sound like a lot, but greatly outstrips other emotional vocalisations such as screams or growls. Not only do we typically underestimate how often we laugh, but we also misunderstand the situations in which we laugh.
The closest distance between two people
Robert Provine has shown that if you ask adults what makes them laugh, they’ll talk about comedy, yet most laughter actually occurs in interactions with other people. We are 30 times more likely to laugh if we are with someone else and, when we do laugh with other people, it is hardly ever because someone has told a joke. Most conversational laughter is produced by the person who is talking.
This suggests that we use laughter to express ourselves. And it’s modified by whom we’re talking to: we laugh more with people we know, or with people we’d like to like us.
I used to think of laughter as a signal that we were amused, but now I see it as an emotional expression of affiliation, affection and agreement. Victor Borge called it the closest distance between two people.
This starts to make a lot of sense when we consider laughter in development. Babies first laugh in interactions ‒ frequently tickling ‒ with their parents and caregivers at around two to three months. Deaf and blind babies will laugh, indicating that they don’t have to see or hear this behaviour in order to produce it; it seems to be innate. If rats are tickled more as babies, they’ll laugh more when tickled as adults: this suggests that the more we laugh, the more we’re likely to laugh.
A few years ago, we found evidence from brain imaging that showed the behavioural contagion of laughter. When people were scanned listening to emotional noises (both positive and negative) we could see activation in auditory areas of the brain and in motor areas used to move the face and make a noise.
The more positive the sounds, the more the activation. We interpreted this as an index of people being primed to respond to heard laughter with a smile or a laugh, even though they’re in a scanner listening to noise. In other words, we’ve spent a lot of time as adults learning to laugh with others.
A more recent study from my lab, however, has shown that the more any listener activates this priming response when they hear laughter, the better they are after the scans at telling whether or not laughter is real or posed.
We’d like to know more about this: if we understand laughter better when we join in with it, what factors affect how we join in? Laughter may be delightful but it may also lead us to understand a lot more about how we manage emotions and social interactions.
Professor Sophie Scott is deputy director of the Institute of Cognitive Neuroscience at University College London. @sophiescott