Farhad Manjoo in Slate:
Bakshy’s study involves a simple experiment. Normally, when one of your friends shares a link on Facebook, the site uses an algorithm known as EdgeRank to determine whether or not the link is displayed in your feed. In Bakshy’s experiment, conducted over seven weeks in the late summer of 2010, a small fraction of such shared links were randomly censored—that is, if a friend shared a link that EdgeRank determined you should see, it was sometimes not displayed in your feed. Randomly blocking links allowed Bakshy to create two different populations on Facebook. In one group, someone would see a link posted by a friend and decide to either share or ignore it. People in the second group would not receive the link—but if they’d seen it somewhere else beyond Facebook, these people might decide to share that same link of their own accord.
By comparing the two groups, Bakshy could answer some important questions about how we navigate news online. Are people more likely to share information because their friends pass it along? And if we are more likely to share stories we see others post, what kinds of friends get us to reshare more often—close friends, or people we don’t interact with very often? Finally, the experiment allowed Bakshy to see how “novel information”—that is, information that you wouldn’t have shared if you hadn’t seen it on Facebook—travels through the network. This is important to our understanding of echo chambers. If an algorithm like EdgeRank favors information that you’d have seen anyway, it would make Facebook an echo chamber of your own beliefs. But if EdgeRank pushes novel information through the network, Facebook becomes a beneficial source of news rather than just a reflection of your own small world.