Researchers at Northwestern University looked at 300 million tweets between September 2006 and August 2009 and using word analysis software, developed Twitter mood maps of the U.S which showed users' moods across the country. (Northwestern University)

The peaks and valleys of people's moods throughout the day can be tracked via Twitter, new U.S. research suggests.

Researchers at Northwestern University in Boston studied Twitter users' changing moods, analyzing them based on geographic location, and showing their evolution on an hourly, daily, and weekly basis. They looked at 300 million tweets between September 2006 and August 2009 and using word analysis software, developed Twitter mood maps of the U.S which showed users' moods across the country.

The researchers found that people were generally happier early in the morning (around 6 a.m.) and late at night (around 10 p.m.). Not surprisingly, people also seemed happier on weekends rather than weekdays, with Fridays showing an uptick in mood as well. Southerners — those living in states such as Florida and southern California — were also found to be in better spirits overall.

The study, at a proof-of-concept stage, has not been published but is available online. The authors acknowledge the results could be biased.

"Since we know the Twitter data contains many biases (for example, tweeters are not a representative sample of the population), what we're working on now is anchoring information in the Twitter data to results obtained from other sources, such as polls and Centers for Disease Control and Prevention data," said Sune Lehmann, a postdoctoral research fellow at the Institute for Quantitative Social Science at Harvard University and the College of Computer and Information Science at Northeastern University, in a blog post Monday.

"This way, we can learn about biases and limitations."