Hunting Gorillas: Perceiving Continuity in Edited Moving Images

How do we perceive films effortlessly when they differ so fundamentally from reality? This is the question Tim J. Smith posed in his lecture at Bristol University’s Vision Institute (BVI). According to Smith, the paradox of film editing is that it creates the impression of continuous action (continuity) by way of discontinuous visual information. Continuity editing creates conditions under which the disruption caused by a cut does not arrest attention. Therefore, continuity editing identifies natural periods of attention withdrawal which can then be used by a filmmaker or editor to hide cuts from a viewer. We will look at the rules of classic continuity editing: first, match on action cutting; second, the 30 degree rule; and third, the 180 degree rule. We’ll also investigate this notion of ‘attention withdrawal’ to address how and why edited moving images are perceived as continuous streams of action.

Attention Withdrawal:

Let’s begin with attention withdrawal. Please watch the selective attention test clip below:

Did you see the Gorilla? This clip presents the idea that perception is often overwhelmed by everyday illusions. In their book The Invisible Gorilla, Christopher Chabris and Daniel Simons present empirical evidence to prove our minds actually miss a lot of what occurs around us. Chabris and Simons present findings on attention, perception, memory and reasoning to reveal faulty human intuition. They also claim to reveal, among other things, “why award-winning movies are full of editing mistakes”. The Invisible Gorilla shows the ways in which our intuitions deceive us, and it appears that continuity editing works within this realm of deception, the selective attention test can help us begin to understand why we succumb to the falsity of continuity editing. When concentrating on an object, like a moving ball, we might not notice something that seems glaringly obvious with hindsight. Perhaps if we try to think through this illusion we may be able to spot some gorillas of our own.

Match on Action Cutting / 30 Degree Rule:

When viewing moving images our attention is cultivated and manipulated, it is shaped both by visual cues within the images and external cues relating to narrative and expectation. In other words we are easily distracted. Our eyes naturally respond to movement and so we track action within a frame instinctively. The DIEM Project collects data from participants watching videos and uses CARPE (Computational and Algorithmic Representation and Processing of Eye-movements) to give an understanding of how humans look, and see. Below is a montage of four visualisations created with CARPE of people’s eye movements as they watch Bjorn Borg and John McEnroe play tennis at Wimbledon.

Essentially, movement focuses our attention and what this video shows us is that a person’s eyes typically follow the movement of the tennis ball around the frame. The use of motion predicts attention whilst simultaneously masking change which is why the match on action cut is so effective. It preserves temporal continuity by focusing our attention on uniform motion within and between shots but action will only continue seamlessly between shots if the 30 degree rule is observed. The 30 degree rule is the convention that states that for consecutive shots to appear seamless the camera position must vary by at least 30 degrees from its previous position. Generally, if the camera position changes less than 30 degrees, the difference between the two shots will cause the viewer to experience the edit as a jump; this effect is jarring and draws attention to itself. The jump cut ruins the illusion of continuity.

“Eyes move around locating interesting parts building up a mental, three-dimensional, ‘map’ of the world.”

There is no example of continuity violation less canonical than formalist Jean-Luc Godard’s self conscious use of jump-cutting in Breathless (1960).

In this clip Godard uses the jump-cut to “draw attention to itself”. While Jean Seberg is in the car talking to Jean Paul Belmondo action seems to jump through time and space. Furthermore, Godard abandons the 30 degree rule by keeping the camera stationary thus facilitating the effect of jumping. The jump-cut ruins the illusion of continuity, it reveals the Gorilla.

So, why is it that the jump-cut jars but the match on action flows? Both are distorting reality. Tim Smith argues that experience is sampled over time, and visual processing limitations necessitate eye movements. Therefore it is the match on action cut and observing the 30 degree rule that works with, rather than against, natural eye movements. Match on action cuts work with the viewers’ automatic eye movements to mask changing shots. Humans and many other animals have evolved eyes that do not look at a scene in fixed steadiness; instead eyes move around locating interesting parts building up a mental, three-dimensional, ‘map’ of the world. Movement within and between frames allows a viewer to order their attention which, according to Smith, replicates the way in which we attend and perceive the real world.

The 180 Degree Rule: 

The 180 degree rule works on the principle that two characters (or objects) maintain the same left/right relationship to each other. If the camera passes the invisible axis that separates the two people the new shot from the opposite side will be at a reverse angle, and the positions of the people will switch. The camera can be placed in any direction, but it must remain on the side of the axis that preserves this left/right relation. If this left/right relation is disturbed the viewer will lose orientation and continuity will be lost.

“Their proximity, coupled with framing and eye line matching, bestows an emotional intensity that grows from a constructed illusion of continuity.”

The 180 degree rule is at its most obvious and effective during a conversation between two people. According to Jean-Luc Godard “the most natural cut in film is the cut on the look. The powerful suggestiveness of this gesture helps explain the film’s love affair with winks, glances, stares, tears, squints, glares and the whole range of languages that the eyes command” the eye and its functions control both perception and emotion. In the below sequence from Léon (1994) we can see a constructed shot-reverse-shot consisting of 37 independent shots.

The sequence appears to elapse seamlessly and unless you’re counting shots you probably wouldn’t consciously perceive the 37 independent shots. The line that keeps the fabric of continuity in place is the eye line match between the characters of Natalie Portman and Jean Reno. If the 180 degree rule was broken during their exchange, their eyelines wouldn’t match and it would be disorienting. It’s a bit like when you’re having a conversation with someone who won’t hold, or match, your gaze.

This sequence from Léon is built around how a person visually experiences the world. In the last few shots of the sequence Portman and Reno are framed in extreme close up respectively. Portman regards Reno with full attention, her eyes moving over his face, a tear wells and drops from her right eye. The shot is reversed, the 180 degree line is observed and their gazes continue to match, Reno now in close-up also has a tear bud and fall from his right eye. Their proximity, coupled with framing and eye line matching, bestows an emotional intensity that grows from a constructed illusion of continuity.

“The limitations of visual processing mean that we can be fooled into perceiving continuity.”

Shot composition and continuity develops both emotional and perceptual passage through this sequence. According to Smith, a film is composed of a combination of endogenous and exogenous cues. Endogenous cues are voluntary and aware, usually embedded in narrative or social events, and exogenous cues are involuntary and unaware, working with (or against) intuition. Smith gives the example of breaking the 180 degree rule in Requiem for a Dream (2000). He says that it takes the viewer longer to order their attention and thus causes a feeling of disorientation. This exogenous cue, coupled with the disorienting nature of the endogenous cues embedded in the narrative, leaves the viewer feeling disoriented and uneasy.


For Smith, the idea of cinematic language or grammar is false because we do not “learn” how to “read” films, we just watch them naturally. He argues that if we remove semantics from film analysis we may begin to understand how our intuitions govern understanding. Organs, like the eye, both see and perceive. Emotion and cognition are entwined. We perceive films effortlessly because they work within natural gaps in our attention. Smith’s Attentional Theory of Cinematic Continuity (AToCC) proposes that experience is universal and ordered around one’s intuition. The limitations of visual processing mean that we can be fooled into perceiving continuity; we are often guided to miss the gorillas that haunt most movies.

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