do moods on twitter follow biorhythms?

NYTimes | However grumpy people are when they wake up, and whether they stumble to their feet in Madrid, Mexico City or Minnetonka, Minn., they tend to brighten by breakfast time and feel their moods taper gradually to a low in the late afternoon, before rallying again near bedtime, a large-scale study of posts on the social media site Twitter found.

Drawing on messages posted by more than two million people in 84 countries, researchers discovered that the emotional tone of people’s messages followed a similar pattern not only through the day but also through the week and the changing seasons. The new analysis suggests that our moods are driven in part by a shared underlying biological rhythm that transcends culture and environment.

The report, by sociologists at Cornell University and appearing in the journal Science, is the first cross-cultural study of daily mood rhythms in the average person using such text analysis. Previous studies have also mined the mountains of data pouring into social media sites, chat rooms, blogs and elsewhere on the Internet, but looked at collective moods over broader periods of time, in different time zones or during holidays.

“There’s just a torrent of new digital data coming into the field, and it’s transforming the social sciences, creating new lenses to look at all sorts of behaviors,” said Peter Sheridan Dodds, a researcher at the University of Vermont who was not involved in the new research. He called the new study “very exciting, because it complements previous findings” and expands on what is known about how mood fluctuates.

He and other outside researchers also cautioned that drawing on Twitter had its hazards, like any other attempt to monitor the fleeting internal states labeled as moods. For starters, Twitter users are computer-savvy, skew young and affluent, and post for a variety of reasons.

“Tweets may tell us more about what the tweeter thinks the follower wants to hear than about what the tweeter is actually feeling,” said Dan Gilbert, a Harvard psychologist, in an e-mail. “In short, tweets are not a simple reflection of a person’s current affective state and should not be taken at face value.”

The study’s authors, Scott A. Golder and Michael W. Macy, acknowledge such limitations and worked to correct for them. In the study, they collected up to 400 messages from each of 2.4 million Twitter users writing in English, posted from February 2008 through January 2010.

They analyzed the text of each message, using a standard computer program that associates certain words, like “awesome” and “agree,” with positive moods and others, like “annoy” and “afraid,” with negative ones. They included so-called emoticons, the face symbols like “:)” that punctuate digital missives.

The researchers gained access to the messages through Twitter, using an interface that allows scientists as well as software developers to work with the data.