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Chemists Know When You've Watched a Scary Scene—Based on Your Breath

ByAllison EckNOVA NextNOVA Next
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All of us emit an invisible cocktail of chemicals while watching a movie.

Nearly ten thousand moviegoers in Mainz, Germany, unknowingly participated in an experiment that revealed their collective responses to various scenes in 16 different films like The Hunger Games 2 , Walking with Dinosaurs , and The Little Ghost . They weren’t spied on by remote cameras, but a device known as a proton transfer reaction mass spectrometer.

Nearly two years ago, chemists hooked up the device to return air vents to sample the type and diversity of airborne molecules floating in the theaters. For a month an a half, they sampled the room every 30 seconds and identified over 100 chemicals each time, a complex potpourri that revealed the audience’s emotions.

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Here’s Anthony King, reporting for Chemistry World:

‘You might expect a vaguely changing mixture, but for many chemical compounds you get a nice consistent and reproducible correlation with events in the film,’ explains Jonathan Williams from the Max Planck Institute for Chemistry, who was one of the researchers involved. For instance, there were discernible spikes of isoprene twice during The Hunger Games 2, when the heroine’s dress catches fire and when the final battle begins. Isoprene is associated with muscle contraction—large spikes were also observed as people entered and left the cinema—so increases during the film could be due to unconscious muscle twitching as the audience empathises with the heroine, Williams suggests.

Scientists have long known that certain emotions prompt specific chemical releases, called pheromones, at least in animals. (In humans, the relationship between pheromones and emotion is less clear.)

What’s striking about this study, though, is that the technique the scientists used was reproducible—particular moments in the films elicited the same pheromones each time. For example, injury scenes were linked to methanol, acetaldehyde, and butadiene. Scientists are still wading through the results, but they could help experts begin to identify some of the invisible signals we send each other when we’re in a strong emotional state.

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