Spoiler alert: Scientists can figure out a movie’s emotional tone from the gasps of its audience. Sure, the sounds are a cue. But so are the chemicals that viewers exhale each time they sigh and scream. These gases could point the way to a subtle form of human communication, a new study suggests.
“There’s an invisible concerto going on,” says Jonathan Williams. “You hear the music and see the pictures, but you don’t realize there are chemical signals in the air.” And they, too, could be affecting you,” says Williams, who led the study. As an atmospheric chemist, he studies the chemical makeup of the air around us. He works at the Max Planck Institute for Chemistry in Mainz, Germany.
Williams started out measuring the air in a soccer stadium. He wanted to see if the fans’ exhaled breaths might affect levels of greenhouse gases in the air. (Greenhouse gases are those that can ultimately help warm the planet by absorbing heat.) Carbon dioxide, which people breathe out, is one example. And the answer was no, he found — at least on a small scale. But he noticed that levels of carbon dioxide and other gases shifted wildly whenever the crowd cheered. That got him wondering. Could the gases people exhale be influenced by emotions?
To find out, he went to the movies.
Williams and his coworkers measured air samples collected over six weeks in two movie theaters. Overall, 9,500 moviegoers watched 16 films. They included a mix of comedy, romance, action and horror films. Among them: The Hunger Games: Catching Fire; Carrie, and Walking with Dinosaurs. The researchers gave scenes from the movies such labels as “suspense,” “laughter” and “crying.” Then they looked for hundreds of chemical compounds in the air that showed up as people were watching particular movie scenes.
And certain scenes had distinct chemical “fingerprints,” the researchers reported May 10 in Scientific Reports.
Scenes that had people laughing or on the edge of their seats were especially distinctive. During screenings of The Hunger Games: Catching Fire, levels of carbon dioxide and isoprene (EY-so-preen) peaked at two suspenseful moments. Because isoprene is involved in muscle movement, the researchers think tense movie moments likely led to its spikes. Williams and colleagues think a bump up in carbon dioxide was due to the viewers’ increased pulse and breathing rates.
The researchers had to account for chemicals in the air that may have had no link to onscreen action. People emit chemicals from their perfume and shampoo. They can even exhale chemicals related to what they snacked on (such as popcorn or beer). During screenings of The Secret Life of Walter Mitty, for instance, the researchers noticed a spike in ethanol linked to a scene in which Mitty orders a beer. Williams speculates that the scene reminded moviegoers to take a swig of their own alcoholic beverages.
Scientists need more data to make stronger links between human emotions and what’s in their breath. But Williams can see potential practical uses. Companies, for instance, could quickly measure the air during tests to see how people feel about new products. He pictures future studies recording other body variables as well. These might include heart rate and body temperature, for instance. “It’s something to investigate.”
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atmospheric chemistry The scientific study of the chemical composition of the atmosphere of Earth or other planets. People who work in this field are known as atmospheric chemists.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter (including fossil fuels like oil or gas) is burned. Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
chemical A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.
chemical signal A message made up of molecules that get sent from one place to another. Bacteria and some animals use these signals to communicate.
compound (often used as a synonym for chemical) A compound is a substance formed from two or more chemical elements united in fixed proportions. For example, water is a compound made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.
ethanol A type of alcohol, also known as ethyl alcohol, that serves as the basis of alcoholic drinks, such as beer, wine and distilled spirits. It also is used as a fuel, often mixed with gasoline, for instance.
greenhouse gas A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.
isoprene A chemical given off by trees, crude oil, some synthetic products and even human breath. It is one of the more common hydrocarbons in the atmosphere and is an ingredient in latex rubber.
J. Williams et al. Cinema audiences reproducibly vary the chemical composition of air during films, by broadcasting scene specific emissions on breath. Scientific Reports. Published online May 10, 2016. doi: 10.1038/srep25464.