So, you're watching a sports film and it seems the stadium is full of people. How did the filmmaker achieve this feat? Well, surely there's only two explanations than can explain such a large congregation of people? Either the studio literally hired, transported, fed and dressed thousands of extras or they resorted to some CGI wizardry to bulk up the crowd.
Well, you've clearly discounted a third possibility - that the crowd is merely thousands of inflatable mannequins with terrifying plastic masks stuck to their faces.
Say hello to the Inflatable Crowd Company
The Inflatable Crowd Company is a Hollywood business which deals in a strange craft. They provide inflatable extras which can be inserted into scenes to give the impression of a massive crowd. Pump them up, throw a wig and some clothes on them and everyone is none the wiser.
The Inflatable Crowd Company has provided mass crowds for movies such as Iron Man 2, Contagion, American Gangster, The Prestige, The Fighter and Blades of Glory. They were even used in Colin Firth's Oscar winning biopic, The King's Speech. Check out the rather nightmare inducing mobs below:
Why Haven't We Noticed?
So, why have we never noticed his gang of emotionless, armless constantly staring zombies? Well, there's a combination of factors.
Firstly, they are usually hidden behind several rows of real actors and are most often only used for wide shots. Secondly, the scenes are also shot with a shallow depth of field, so as to further prevent us from noticing.
We see things that aren't always there
However, there is another, psychological element occurring here. Researchers from the University of Glasgow claim that the brain is built in order to fill in the blanks, even when our vision is obscured. This means, when presented with a portion of a crowd, we will automatically 'see' the remainder of the crowd, even if its individual components are obscured - or indeed, an inflatable dummy wearing thrift shop clothes. This is called predictive coding and it suggests the "brain actively predicts what input it will receive, rather than just passively processing information as it arrives." As Dr Lars Muckli, from the University’s Institute of Neuroscience and Psychology explains:
We are continuously anticipating what we will see, hear or feel next. If parts of an image are obstructed we still have precise expectation of what the whole object will look like.
When direct input from the eye is obstructed, the brain still predicts what is likely to be present behind the object by using some of the other inputs to come up with best ‘guesses’.
It's all because of our survival instinct
Dr Muckli claims this ability primarily developed to aid the survivability of our ancestors, as we can predict what is unseen based on what is seen - an ability which is relatively rare in the animal world. This predictive coding allowed us to respond to situations quickly, and more importantly to 'predict the future'. Muckli continues:
Memory and the predictive power of the brain combine in a very powerful way to allow us to anticipate our surroundings. Any kind of predictive method is an advantage to a biological system.
Although this advantage was originally developed to save us from sabre tooth tigers, it also turns out it's quite useful for watching movies too!