Is it possible to laugh alone? There are certainly times when we burst out laughing all by ourselves. But usually, we think of laughter as a group activity.

In the classic Laughter: An Essay on the Meaning of the Comic, Henri Bergson wrote, “However spontaneous it seems, laughter always implies a kind of secret freemasonry, or even complicity, with other laughers, real or imaginary.” To laugh alone is to remember the social atmosphere of past laughter: the giddiness over cocktails, the scrunched-up face of the curmudgeonly aunt.

For most of human history, entertainment was a public affair, and theatergoers experienced comedy as a crowd. This was also true of cinema. When the Marx Brothers started making movies in the 1930s, they could be sure that laughter would roll through the mo...