Like most people, I like funny things. I like to be funny; I delight in cracking people up. But I’ve always wondered about it, and more broadly in the context of why we like comedians (because I really enjoy a good comedian, thinking of Dave Chapelle and Tom Segurra especially).

The notion that the chorus of the Greek tragedy was a subject of serious philological debate. predates my curiosity about laughter and partly inspired it. I remember reading about The Birth of Tragedy and was struck that this element of a Greek play—a group of performers that spoke in unison—remained a source of intrigue… that its function, separate from the audience’s acceptance of it, was something of a mystery.

So to with laughter, perhaps?

Why do we laugh? What function does it perform? If it even does?

[I]ts principal function appears to be creating and deepening social bonds. As our ancestors began to live in larger and more complex social structures, the quality of relationships became crucial to survival. The process of evolution would have favoured the development of cognitive strategies that helped form and sustain these cooperative alliances.

This article differentiates between two kinds of laughter: volitional and spontaneous. There are audible differences between the two, and people can reliable detect one from the other. But both types fulfill the same need.

In the same vein, but with an added caveat: Laughter is a sign of safety:

“The idea was that laughter was an external signal that can tell the group everything is OK, we can relax. (There is) no need to be anxious or threatened by what’s happening around us. And so this would really be a great survival tool for groups of humans,” she explained.

But what about watching a comedian or comedy with others? Why do we like that?:

This form of (Duchenne) laughter is involuntary and highly contagious (we are up to 30 times more likely to laugh when we watch a comedy video in a group than if we watch the same video alone

Most research on the functions of laughter has focused on the information being broadcast by the person laughing or its role in inducing positive affect in the listener, thereby facilitating interaction or reducing threat

As mentioned above, there is the kind of laughter I was curious about: spontaneous laughter, or what is also called Duchenne laughter (named for the scientist who discovered the physiology of a spontaneous smile). But there is another kind of smile, and a corresponding kind of laughter: volitional. Unlike spontaneous laughter, the telltale sign is the eyes. Interestingly, such laughter is punctuational… calculated, even:

The results were surprising, even to Provine: Less than 20 percent of the real-world laughter incidents he cataloged were in response to anything resembling something funny. Far more often, people were giggling or chuckling at innocuous statements such as “I’ll see you guys later,” “I see your point,” and “Look, it’s Andre!” What’s more, in all of these cases, the person who produced the laugh-provoking statement was 46 percent more likely to be the one chuckling than the person listening. And while laughter might seem like something that can erupt at any point in response to something funny, in only eight of the 1,200 laugh episodes Provine cataloged did the laughter interrupt what somebody was saying. Instead, 99.9 percent of the time, laughter occurred in tidy, natural breaks in the conversation, punctuating the speech like a period or exclamation point.

Applying the prongs of his box to people’s faces, Duchenne evoked one kind of smiling—the voluntary kind, the type of expression we produce when we a grin to be polite. This mannerism, he discovered, involves the face’s zygomatic major muscles raising the corners of the mouth. But Duchenne discovered there was a second variety of smiling and laughing, one that occurs when we find something truly entertaining or funny. This expression was more complex, utilizing both the zygomatic major muscles and the orbicularis oculi muscles that form crow’s feet around your eyes. It’s why people say a real smile is in the eyes. Duchenne was never able to reproduce with his electrodes this second form of expression—now known as a Duchenne smile or Duchenne laughter—and he came to believe it was “only put at play by the sweet emotion of the soul.”

But then, sometime in the hundreds of thousands of years after that, theorized Gervais and Wilson, the other sort of laughter emerged—the non-Duchenne sort, the kind that isn’t dependent on something being funny. As people developed cognitively and behaviorally, they learned to mimic the spontaneous behavior of laughter to take advantage of its effects. They couldn’t get it right—they couldn’t simulate the eye-muscle movements of real laughter and smiling—but it was close. Mimicked laughter was a way to manipulate others—sometimes for mutually beneficial purposes, sometimes for more devious reasons. As Gervais and Wilson put it in their paper, “non-Duchenne laughter came to occur in aggressive, nervous, or hierarchical contexts, functioning to signal, to appease, to manipulate, to deride, or to subvert.”