In the world of Facebook, users are either kings or lemmings. That's the conclusion of a new study, the largest to analyze how information spreads across social networks-and who does the spreading.
The debate about how ideas, opinions, and behaviors radiate within groups of people goes back decades. According to the so-called influentials hypothesis, made popular by books such as "The Tipping Point," by Malcolm Gladwell, a small number of highly influential people drive most of the spread. For example, if the popular kids in a high school get iPhones and all the other kids soon follow, the hypothesis says that it was because of the sway of the cool kids. But critics counter that influential individuals play only a minor role, and what matters is whether people are susceptible to the new idea.
The debate has remained unsettled because studying peer influence is notoriously difficult. Studies of the real world are messy and rarely allow for controlled experiments, whereas social experiments in laboratories are expensive and involve contrived situations. So, researchers are turning to online social networks such as Facebook. Such approaches make it easy to track the behavior of huge numbers of people, while third-party software applications, or apps, allow researchers to run virtual experiments on Facebook users, often for free.
To test peer influence, Sinan Aral and Dylan Walker, economists at New York University's Stern School of Business, used a Facebook app that allows users to rate and recommend movies. (Aral and Walker are keeping the identity of the app confidential at the request of the company, but they say that it is similar to Flixster.) As users interact with the app - for example, you give the 2011 movie "The Tree of Life" four out of five stars - it sends messages to a random selection of your Facebook friends notifying them of the rating and providing a link to the app. The more friends that adopt the app after receiving a notification from you, the greater your influence. The shorter the time period between receiving a notification and adopting the app yourself, the higher your susceptibility.