A guy walks into a blog and wonders why people laugh.
Humour depends on culture, but laughter seems to be universal. Apes respond to tickling with a panting that resembles laughing. Some other animals may also respond to tickling, but it harder to tell if they are laughing.
Neurologists say laughter in humans comes in two main flavours. The Duchenne laugh (named after a French neurologist from the 1800s) happens spontaneously when we get tickled or when we think something's funny. Many parts of the brain are activated with this emotional release.
This sort of laughter is generally a release from tensions built up from unmet expectations. We think someone might do us harm, but they tickle us. You can't tickle yourself because you know what to expect. We think something will be one way and it turns out to be so different that it is funny.
The non-Duchenne laugh follows different neural pathways and relies on a social setting, not necessarily connected to something funny. You might not realize it, but this is the most common form of laughter, though perhaps not as much fun to study.
Human babies start laughing around 3 to 4 months of age. They can make some sounds apes cannot. Babies rely on parental care and laughter seems to be important for strengthening bonds between adults and infants. Mothers (and other adults) laugh about twice as much as infants. Mothers who laugh more have infants who laugh more. I don't think they've found a laughter gene yet, because most behaviours depend on nurturing as well. Children laugh more as they get older and the kinds of things that make children laugh increases as their understanding of language develops.
Laughing has been cited as having various physiological benefits, but these are probably secondary to the social benefits. Non-Duchenne laughter seems to help promote social cohesion. The rate of laughter is similar in groups of friends as it is in strangers. Women laugh more than men, though it's not clear how much of this is the result of socialization. In personal ads, women are more likely to seek a sense of humour and men more likely to offer it. Speakers tend to laugh more than their listeners. Laughter can be contagious and the two forms may overlap. After a TV show added the first laugh track in 1950, people did think the jokes were funnier.
Do have any observations about laughter to share?