The new tool tells you which friends make you the happiest via their Facebook activity. After determining who your top 25 friends are, it analyzes their posting behavior, and then lists them from most the positive to the biggest bummers.
The app relies on the notion that emotional Facebook posts are contagious. The theory was first considered by a team of researchers who analyzed over one billion status updates between January 2009 and March 2012, and concluded the emotions expressed in your friends' Facebook postings are likely to affect the way you feel as well.
It makes sense. If most of your friends are posting about how awful the weather is, or how awful Fox News is, or how awful the Mets are, you're going to feel, well, awful. But, if your friends are posting about how great snapbacks are, or how great their trip to Italy was, or how great last week's episode of Game of Thrones was, you're going to feel, well, great.
To find out who among your friends are the biggest killjoys, and who are the biggest merrymakers, click here. (TIME)