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When we breathe, we emit chemicals into the air that are very telling. Scientists discovered that they can even reveal what kinds of movies we’re watching.
Researchers from the Max Planck Institute for Chemistry and Johannes Gutenberg University recently studied the chemicals in the air during showings at a movie theater. Among others, they monitored carbon dioxide, isoprene, and acetone, during 108 screenings of 16 different films at the Cinestar Cinema complex in Mainz, Germany from December 2013 to January 2014. The showings included family-friendly films like Walking with Dinosaurs and The Secret Life of Walter Mitty, comedies like Buddy, and major film franchises like The Hunger Games 2 and The Hobbit: The Desolation of Smaug.
In some cases, they found that the chemical composition of the air was tied to the on-screen action. During The Hunger Games 2, for example, the level of isoprene, which can increase in the breath when people move, jumped during two key scenes: when Katniss Everdeen’s dress catches fire and when the film’s final battle begins. This suggests that viewers held their breaths or that their muscles twitched during those scenes, the study said. Isoprene in the breath also signals cortisol production, which prepares the body for fight-or-flight mode, among other functions, the study pointed out.
Some genres like “comedy” and “suspense” could also be identified based on the chemicals in the air, the study found. “Injury” scenes, which the study categorized under “suspense,” were linked to the chemicals methanol, acetaldehyde, 2-furanone, and butadiene. Many other genres, like romance, did not have strong ties to particular chemical compositions and could not be identified based on breath. It may be awhile before this type of analysis can be used to accurately measure audience reactions.
The study found that the chemical patterns of the air were similar during different showings of the same movie, which suggests that theatergoers consistently had the same physiological responses to what happened on-screen.
Here’s what the chemical levels looked like during four separate screenings of The Hunger Games 2, as an example: