Scientists can tell what kind of movie you're watching based on the chemicals in your breath

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Looks like a horror movie, but what does it smell like?

When a movie studio wants to find out what audiences think of their films, they usually have to wait for focus group responses or reviews. But what if they could get instant feedback from viewers' breath?

Researchers from the Max Planck Institute for Chemistry and Johannes Gutenberg University measured the chemicals in the air during 108 screenings of 16 movies. These were as diverse as "The Secret Life of Walter Mitty," "Buddy," "The Hobbit," and "The Hunger Games."

Apparently, the scientists could determine what sort of movie had been screened based on those chemicals, as well as how the audience reacted to it, on a scene-by-scene basis.

"The chemical signature of 'The Hunger Games' was very clear; even when we repeated the measurements with different audiences," Jonathan Williams, one of the study's authors, wrote. "The carbon dioxide and isoprene levels in the air always increased significantly as the heroine began fighting for her life."

The researchers suggested that chemical changes are caused by the way we breathe during certain scenes. In suspenseful scenes, for example, the audience members become tense and breathe faster, excreting more adrenaline and cortisol.

It's hard to tell how useful this research will be. One application, The Wall Street Journal suggested, is for advertisers. Since they will be able to track specific points of time in a movie, they will be able to tell how audiences are reacting to their product placements.