We all know that things go viral. Someone’s cat, or a dancing baby. Or that dress – the one that was either blue and black or white and gold. But where does a viral picture or meme start? What spreads one idea around the world and leaves another one dead on the screen?

One researcher at Northeastern University is trying to figure it all out. With his computers gathering data day and night, he’s looking for the roots of what is now known as the “viral cascade.”

Devin Gaffney says that no one can pinpoint the exact reason, but one of the factors is something called homophily. It’s the idea that people on the Internet, like those in the real world, interact with those who are most like them. And live closest to them.

WBUR