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Fields & Applications Mass Spectrometry, Chemical

Baited Breath

A team at the Max Planck Institute for Chemistry in Mainz, Germany, have discovered that film fans can change the chemical composition of the air around them – with their breath. The team screened 9,500 people for potential emotion signaling molecules during 108 screenings of 16 different films. They found that the chemicals emitted varied from scene to scene, allowing them to pinpoint exact moments in the film that elicited strong emotional responses.

Originally, the team were looking to answer a different question: are the chemicals that we breathe out significant to global atmospheric chemistry? The group decided a trip to the football stadium might help. “With 30,000 people in a confined space you can get a nice average breath spectrum. Based on that we could multiply the average by 7 billion people and see whether the numbers were in any way important on a global scale,” says Jonathan Williams, from the Air Chemistry Department. From that came the idea of capturing the “chemistry of group euphoria”. Williams says, “We thought it would be cool if, when there was a goal and everybody got ecstatic at the same time, we could capture the chemical signature of a goal!”

Figure 1. a) peaks in CO2 over five days of film screening. The levels increase rapidly as audience members enter the auditorium and fall off sharply as they leave; b) CO2 measurements for four film showings.

The higher the CO2 measurement, the higher the attendee numbers; c) CO2 measurements throughout a showing of “Hunger Games 2”. The small peaks in CO2 suggest momentary increases in pulse and breathing rate in response to key moments in the film.

Unfortunately, the match ended 0-0. The team decided that a movie theater could be an good substitute location. “A cinema is a really elegant way of measuring the potential linkage between what we breathe out and our chemical state of emotion,” Williams says. “We essentially got people in a nicely ventilated box and then frightened them or made them laugh. All the time we flowed air over them, and simply measured the sequence of peaks. We were able to measure on-line, so could see clearly and in real time when everyone was frightened and we got a peak in CO2.” Film events labeled “suspense” or “injury” elicited the strongest chemical changes, leading the team to speculate that this “chemical communication” may function as a form of group signaling beneficial from an evolutionary perspective.

They used Ionicon’s proton transfer reaction mass spectrometer (PTR-MS) to track the trace gases. “It runs on water – you essentially pass a lightning bolt through it and that forces the water to carry an extra proton, giving you H3O+ instead of H2O,” Williams says. “You simply put these reagent ions through ambient air, and they try to pass on that uncomfortable extra proton. Fortunately for us, the proton does not transfer to nitrogen, oxygen, argon – all the main components in the air – so we are able to detect a whole host of organic species with the system – acids, alcohols, aromatic compounds, and so on.”

Figure 2: Measurements of CO2, isoprene and acetone during four separate screenings of “Hunger Games 2”. The red markers show moments where audiences had reproducible responses to the same moments in the film. The two peaks in isoprene suggest breath-holding, and correspond with the heroine’s dress catching fire and the final battle.

A crucial advantage to conducting the experiment in a cinema was reproducibility. “I looked at the results for The Hunger Games 2 and noticed that when the same film was shown on a different day to a different 250 people, for some of the chemicals the peaks occurred in the same place,” says Williams. “Of course, as a scientist – and especially as an analytical scientist – you want reproducible results. In a cinema, you can do that by showing a film multiple times.”

Williams describes the paper as “a signpost publication” and says he would expect a lot of atmospheric chemists to be interested in developing the findings further. “These temporal changes in chemistry are there to be seen in a group of people in a controlled environment – and you can use those signals for whatever purpose,” Williams says. He suggests it may also have uses in biology, film-making, advertising and psychology: “A lot of psychologists try to do experiments where they attach probes or have to wear a mask – which can influence behavior. To be able to non-invasively measure someone’s reactions could be very useful.”

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  1. J Williams et al, “Cinema audiences reproducibly vary the chemical composition of air during films, by broadcasting scene specific emissions on breath”, Sci Rep 6, 25464 (2016). DOI: 10.1038/srep25464
About the Author
Joanna Cummings

A former library manager and storyteller, I have wanted to write for magazines since I was six years old, when I used to make my own out of foolscap paper and sellotape and distribute them to my family. Since getting my MSc in Publishing, I’ve worked as a freelance writer and content creator for both digital and print, writing on subjects such as fashion, food, tourism, photography – and the history of Roman toilets. Now I can be found working on The Analytical Scientist, finding the ‘human angle’ to cutting-edge science stories.

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