On May 19th, 2016 we learned about

Chemical emanations may reveal our emotional state

It turns out the idea of “smelling fear” might not be so off the mark. Humans, like all living things, emit various gaseous byproducts all the time, most of which we’re not consciously aware of. However, it seems that the makeup of those gases shifts with our moods, and that some emotional experiences can somehow trigger detectable changes in our collective smell.

Emotionally-oriented odors weren’t discovered thanks to an individual with really strong reactions, but with really big crowds. Over the course 108 screenings, 9,500 test participants’ air supply was monitored for changes in composition. A device called a proton transfer reaction mass spectrometer (PTR-MS) was used to pick detect 100 of the 872 volatiles humans are known to emit, allowing researchers to “smell” changes in the room with great sensitivity. Notable spikes in a single compound were then matched to the content in the movie at that moment, looking for correlations between particular moods and odors.

The chemical traces of tension

The strongest shifts in volatiles came when the audiences were watching something funny, or when there was a scene building tension or depicting injury. For example, a scene in The Hunger Games: Catching Fire that depicts the protagonist struggling with her burning dress matched a spike in isoprene in the theater. Isoprene is generally understood to be tied to muscle activity as well as cholesterol synthesis. Researchers can’t be sure yet if the increased isoprene detected was due to the collective tensing of muscles as viewers worried about their heroine, or if it was tied to the stress hormone cortisol via cholesterol. Another bump in isoprene was detected when audience members left the theater, probably due to muscle activity, but that was a lot more activity than nervous viewers gripping their armrest in excitement, so it’s unclear what the exact cause was.

The other question is if these volatile compounds serve an evolutionary purpose, or if they’re just a byproduct of metabolism. While we don’t consciously notice subtle odors like this, it’s possible they offer a non-verbal form of communication for moments of potential danger, or in the case of comedy, a signal that all’s clear. If it isn’t serving our biological noses, detecting changes in mood with electronic noses may still be of value. At a minimum, it can be used to gauge reaction and mood when test audiences screen next year’s big blockbusters.

Source: The chemicals we off-gas change when we watch something funny or thrilling by Beth Mole, ArsTechnica

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