When I was a child in the 1980s, my relationship with split screens began and ended with the opening credits of glamorous prime-time TV dramas. Even now, my breath catches at the thought of those introductory Dallas triptychs. Patrick Duffy! Linda Gray! These were people so momentous that you got three of them at once. Dynasty had its own classy variation, whereby a panel containing the actor overlaid a background scene. Think of a brunet soap hunk smouldering in a vertical stripe, which partially covers a bottle of frothing champagne.

My younger self’s association of split screens with campy decadence was, of course, a limited perspective. The technique is nearly as old as video technology itself. The director Edwin S. Porter, for example, deployed it in 1903, in his short silent film Life of an American Fireman. In the opening scene, a drowsy fire chief sits in his office chair, and in a hazy circle above him we see, as through a porthole, into another place, where a woman is tucking a child into bed. The double image is ambiguous: Is this the fireman’s dream of his actual home, or a home life he wishes he had, or a memory, or is it meant simply to represent something happening at the same time, whether related to him or not?

Photograph: Alamy 

Porter soon connects these collided scenes: When the fire bell sounds, the firemen go to the house of the woman and child, which is now filled with smoke. Their relationship to the fire chief, however, remains mysterious, and this mystery springs from the strangeness of the split screen itself: Does it bind two events together or diametrically oppose them? Are both things happening, or only one of them, or neither of them? The split signals a fork in the road, the twist being that both paths—taken and not—exist in parallel. More than a century after Porter’s film, in 500 Days of Summer, the drama bifurcates into “Expectations” on one side and “Reality” on the other.

How resonant the split screen is now, as we inevitably set our expectations for the autumn and winter of 2020 against the reality. The shock of lockdown makes it tempting to imagine that the real you is inhabiting a parallel stream of events, cavorting unmasked in one Dionysian gathering after the next, while this other you scrubs down your mail. But even before pandemic struck, the prevalence of split screens was encouraging us to shape and articulate our experiences in this partitioned way. The more of them we encounter, the more we begin to interpret the world according to their logic.

For many years, a major function of the split screen in unscripted TV has been to set up a gladiatorial relationship between the speakers. They may be geographically and ethically removed, yet the split screen hinges them together. One of the most infamous split screens in 21st-century American television involved two people sitting a table-length from each other. It is catalogued in the glossary of Ladies Who Punch, Ramin Setoodeh’s book about the morning talk show The View, as the “split-screen incident” of 2007.

During cohosts Rosie O’Donnell and Elizabeth Hasselbeck’s increasingly heated argument about the Iraq War, the audience at home got a view of both women at once. This technique had never before been used during the show’s “Hot Topics” segment. When O’Donnell noticed what was happening on a monitor, Setoodeh reports, she became even angrier. The aggression of the format was arguably more upsetting to her than the content of the fight. “When I saw the split screen,” O’Donnell said later in a video on her website, “I knew it was over.”

Since then, split screens have become relatively simple to produce outside the professional studio. On social media, “reaction videos,” in which people film themselves responding to a piece of embedded video, are a popular variation on the genre. Users might react to a makeup tutorial, a news clip, or their first time listening to a vintage hit. These videos imply that all the world really is a stage. Both a performance and the experience of that performance are performed, side by side. Reaction videos dramatize the intense self-consciousness of our digital age, which continually invites us to place ourselves inside an event, to individualize mass, pop-cultural moments with our comments, our emojis, our tweets, and our blissed-out grimaces to Sinéad O’Connor’s “Nothing Compares 2 U.”

While reaction videos cleave an artwork into its substance and its effects, the split screen is also being used on social media for the purposes of political activism. One recent viral video by Momentum, an organization affiliated with the UK’s Labour Party, sets footage of New Zealand prime minister Jacinda Arden’s various announcements about her successful pandemic strategy alongside those of the UK government, which currently presides over the worst death toll in Europe. On the topic of herd immunity, Arden says: “That would have meant tens of thousands of New Zealanders dying, and I simply would not tolerate that.” Cut to the right-hand side of the screen-cum-boxing ring, where British prime minister Boris Johnson “replies” with the idea that “perhaps we could sort of take it on the chin, take it all in one go, and allow the disease, as it were, to move through the population.”