Twitter selfies may reveal our moods....

In fact, by analyzing 1 million photos tweeted over a period of one year, researchers are planning to measure the "moods" of some American cities. The team will correlate the Twitter image data with other sources of happiness data, such as the Gallup Poll results.

One of the project's highlights will be an analysis of selfies that people post on Twitter, to see whether, for instance, people who live in "happier" cities tend to post more selfies, and whether they smile more while taking self-portraits.

The researchers will focus on images, as opposed to the words, in tweets, because "mages may transcend the limitations of language."