The changes in any one person’s breath might be minuscule, but a crowd of breathers could be enough to overcome the rest of the background signals. And more importantly, unlike a soccer match, the experiment could be done with the same film again and again. This could test the reproducibility of findings, which is critical to science.
Rigging a mass spectrometer into the outflow vent of the theater, the Kino Cinestar in Mainz, Williams had a sense that the experiment as something of a lark. “I thought, we’re probably just going to get a big mixture of popcorn and perfume,” he said. But, nonetheless, to measure relationships between scenes and gases, his team meticulously mapped out and labeled every scene in 16 films—from beginning to end. In 30 second increments, the team labeled each by its quality (kiss, pet, injury), as well as its emotional elements using a finite set of descriptors.
Their efforts were not entirely wasted. They published the findings this month in Scientific Reports, an open-access journal published by Nature. After measuring more than 100 chemicals in the theater air from 9500 filmgoers, the team saw some changes that stood out—at the same points, in almost every showing of some films.
In Hunger Games: Catching Fire, for example, during the “suspense” scenes—when Jennifer Lawrence was in particular danger—the carbon dioxide, acetone, and isoprene levels in the theater air predictably increased. The researchers speculate that this may have something to do with breath-holding, or stress hormone production—but it is all speculation. The important point was that the signals occurred at exactly the same time in all four screenings of the film. They also found the reproducible changes in the air chemistry during “humor” scenes in other films.
It’s impossible to say whether the changes in the air are signals to one another, or simply byproducts of emotion-based reactions. To Williams, that’s “the billion-dollar question.” But he is guarded in his excitement. “We have shown there is this invisible, inaudible concert of chemicals that changes regularly in the auditorium. We haven't shown that people can detect them. But, of course, if a signal is there, then maybe it does.”
“The authors do make a very important point about the effects of stress or anxiety on human emissions,” said Ben De Lacy Costello, a senior research fellow at the University of West England. He created a catalog of all the chemicals we emit and found at least 1840 . Though it was published in The Journal of Breath Research, the list included volatile organic compounds (VOCs) coming from many parts of healthy people: 359 in saliva, 154 in blood, 256 in breast milk, 532 in skin secretions, 279 in urine, and 381 in feces—in addition to 872 in our breath.
Williams and Costello, among others who study air and perception, refer to the volatile chemicals we humans emit as the volatolome. It’s a linguistic construction akin to our genes collectively being called our genome, and our microbes making up our microbiome.