How Algorithms Discern Our Mood from What We Write Online

Did 2020 seem like the worst year ever to you? While such a description may seem hopelessly subjective, according to one measure, it’s true.

That yardstick is the Hedonometer, a computerized way of assessing both our happiness and our despair. It runs day in and day out on computers at the University of Vermont (UVM), where it scrapes some 50 million tweets per day off Twitter and then gives a quick-and-dirty read of the public’s mood. According to the Hedonometer, 2020 was by far the most horrible year since it began keeping track in 2008.  It's ticked back up again in 2021—we're a little happier, at least collectively on Twitter, than we were in 2020—but this year is no basket of puppies and rainbows either.

The Hedonometer is a relatively recent incarnation of a task computer scientists have been working on for more than 50 years: using computers to assess words’ emotional tone. To build the Hedonometer, UVM computer scientist Chris Danforth had to teach a machine to understand the emotions behind those tweets — no human could possibly read them all. This process, called sentiment analysis, has made major advances in recent years and is finding more and more uses.

In addition to taking Twitter user’s emotional temperature, researchers are employing sentiment analysis to gauge people’s perceptions of climate change and to test conventional wisdom such as, in music, whether a minor chord is sadder than a major chord (and by how much). Businesses who covet information about customers’ feelings are harnessing sentiment analysis to assess reviews on platforms like Yelp. Some are using it to measure employees’ moods on the internal social networks at work. The technique might also have medical applications, such as identifying depressed people in need of help.

Sentiment analysis is allowing researchers to examine a deluge of data that was previously time-consuming and difficult to collect, let alone study, says Danforth. “In social science we tend to measure things that are easy, like gross domestic product. Happiness is an important thing that is hard to measure.”

Deconstructing the ‘word stew’

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