When was the last time you watched a comedy movie or a sitcom by yourself. Did you laugh out loud? Most people do not laugh alone, but when other people are around, they laugh up to 30 times more. Laughter is an incredible social phenomenon, one that led researchers to hypothesize that it evolved to boost social bonding and cooperation. The presence of other people, and especially their audible laughter, helps to increase laughter all around. This contagious laughter effect is well known to comedy shows producers, who use laugh tracks to boost audience laughter.
When people share a laugh with others, their overall experience is much more positive and emotionally strong, and they perceive others to be nicer. Moreover, Robin Dunbar hypothesized that laughter evolved to serve as social grooming, just like other animals groom each other. Grooming is important in the animal kingdom for many reasons. For example, grooming helps individuals to clean each other, facilitate reconciliation when conflicts arise, and generally help individuals to feel closer to one another.
Usually, social grooming is conducted in dyad interactions, so it is affecting two individuals. Laughter, on the other hand, can be shared among many people at the same time. But does it have the same impact? In other words, is there an ideal number of people that can share a laugh before its effects are diminished? A new study tried to answer this question.
The best way to study laugher is by observing people in natural conversations. Researchers went to bars across Europe (mostly in the UK) and listened to people’s conversations, documenting the group size and how many people laughed at any given time. Previous studies show that the optimal number of people that can interact in a spontaneous conversation is four. More than that and it becomes too noisy and messy. However, when they looked at laughter, they found out that the optimal number of people to share a laugh is slightly smaller, with 3.35 people on average.
This relatively small number of people laughing in a group is somewhat surprising. It makes some sense because in order to laugh, people need to understand the joke being told to them, and in a large group this is a more difficult task. However, people also laugh even if they didn’t understand or hear the joke, and moreover, people tend to laugh just because other people laugh around them and not merely because of what they say.
So, did evolution find an excellent way to groom several people at the same time, what the authors call “grooming-at-a-distance”? Maybe. Dunbar (one of the co-authors on this study) has famously proposed that the optimal group size in which people can maintain social interactions is around 150. This was approximately the number of people in a group of our ancestral hunter-gatherers. This number is much larger than most other primate group sizes, so the “classic” one-on-one grooming is not very efficient, and other mechanisms of grooming would need to take place. Laughter can increase the number of people that are groomed with relatively little effort. So next time you are in a bar or with friends, you can observe social grooming in action and think about how deeply rooted in your evolutionary history it might be.