The Experiment

In the early 1920s, Soviet filmmaker Lev Kuleshov ran a simple test. He took a shot of an actor’s blank, neutral face and cut it together with three different follow-up shots: a bowl of soup, a coffin containing a dead woman, and a child playing. Shown these sequences, audiences swore the actor’s expression changed each time. They saw hunger when the face was paired with soup, grief when paired with the coffin, warmth when paired with the child.

The actor’s face never changed. Kuleshov used the same footage every time. What changed was the shot next to it, and the viewer’s mind did the rest, filling in an emotion that was never actually performed or filmed.

This became known as the Kuleshov effect, and it’s one of the foundational ideas in film editing theory. It suggests that meaning in cinema isn’t only located inside individual shots. It’s generated in the space between them, in the cut itself.

Why It Works

The effect works because human perception is built for inference, not just observation. We don’t watch a sequence of unrelated images so much as we build a story to explain why those images were put next to each other. Show a neutral face and then a threatening object, and the brain assumes causation: the face must be reacting to the threat. That assumption happens fast, below the level of conscious analysis, which is exactly why it’s so useful to filmmakers and so invisible to audiences.

Alfred Hitchcock, who understood audience psychology as well as anyone who ever worked in the medium, used to describe a version of this same idea using a man looking out a window. Show the man, then show a woman with a baby, cut back to the man smiling, and he’s a kind neighbor. Swap in a woman in a bikini and cut back to the same smiling shot, and he’s a dirty old man. The man’s face, and the actor’s performance, never move. Only the object of the cut changes, and with it, the entire read on his character.

Beyond the Lab

Kuleshov’s experiment was academic, but the principle runs through everyday filmmaking far beyond montage sequences. Reaction shots are Kuleshov effect in practice: a character’s blank stare, cut against whatever they’re supposedly looking at, tells the audience how to feel about that thing without a line of dialogue. Horror relies on it constantly, cutting between a character’s face and an empty hallway to manufacture dread the actor never performed in the room. Comedy uses it for the opposite effect, cutting to a deadpan reaction shot to defuse or amplify a joke.

It also explains why editing has so much power over performance. An actor can give a take that reads as ambiguous on its own, and the editor can steer that ambiguity toward fear, suspicion, or affection just by choosing what comes before and after it in the timeline. This is part of why the same raw footage can be cut into a trailer that feels romantic or one that feels ominous. The performance is identical. The juxtaposition isn’t.

Unscripted television and reality shows lean on this constantly, cutting reaction shots recorded at completely different moments into conversations to manufacture tension or alliance that may not have existed on the day.

The Editor’s Real Power

The Kuleshov effect is a reminder that an editor isn’t just trimming a director’s footage into a more efficient shape. They’re actively deciding what a scene means, sometimes overriding what was actually performed on set. A director can hand over dozens of neutral, ambiguous takes and trust the cutting room to build the emotional through-line the footage doesn’t show on its own.

It’s also a useful piece of media literacy for anyone watching closely. The next time a reaction shot lands with more feeling than the actor’s face seems to justify, the emotion probably isn’t coming from the performance at all. It’s coming from whatever the editor cut next to it.