In the early 1970s, the psychologist David G. Myers conducted a famous experiment on the power of groups. He divided several hundred undergraduates into two camps based on their attitudes toward feminism, creating a conservative cluster and a liberal one. Then he left them all alone to talk. When the groups disbanded, the liberal students had become much more liberal, and the conservative students had veered sharply right.
Today this effect is known as group polarization, and unlike other pseudo-phenomena in the field of psychology, it’s been ratified by several additional studies. Spending long amounts of time with people who agree with you doesn’t just lead to groupthink, these researchers have found; it can also lead to the gradual silencing of dissent and the elevation of, and consensus around, the most virulent opinions. If you want to make people more extreme, you don’t have to threaten them or brainwash them. Just plop them in a like-minded group, and human nature will do the rest.
What does this have to do with the internet? Approximately everything. Social networks such as Facebook and Twitter are many things at once—a modern railroad crossed with a modern telephone network, mixed with a modern phone book, on top of a modern Borgesian library. Above all, social media are a mechanism for allowing people to find like-minded individuals and to form groups with them. To a technologist such as Mark Zuckerberg, this characteristic seemed to promise a new age of transnational peace and moderation (not to mention: profit). But to a social psychologist, it sounded like a machine for injecting public discourse with ideological steroids.