narily rare and somewhat arbitrary. If you're a social media strategist or a digital advertising agency, basing a marketing or other strategy on triggering a social epidemic is probably not the best use of your resources.
You are also investigating the nature of cooperation between people. How is that related to the spread of ideas?
The spread of information and the spread of cooperation are both examples of social influence, so they're related, at least in principle. But it's also important to understand that different types of influence are likely to spread in different ways. Me persuading you to change your political views is very different from me persuading you to click on a video.
People do not easily adopt ideas that involve changing their conception of themselves. Not accepting the idea of climate change might be tied up with your political ideology, your suspicion of government and your dislike of elite intellectual types. When is an idea something that you can adopt just because it's obviously right or obviously interesting? And when is it something that is going to be very difficult for you to adopt because it's tied up with all these other things?
What are the stakes?
This is not about cat videos going viral, even if sometimes that's what we study because it's what we have the most data about. Really, it's about changing people's minds, and their behavior; and one way or another, everyone – governments, corporations, marketers, policymakers – is in the business of trying to change people's minds. Understanding how that happens is one of the big questions of social science. It's frustrating that we've been thinking about this for so long and have very little in the way of concrete answers. But maybe this particular period of history is different. That's the hope.
Duncan Watts is a principal researcher at Microsoft Research NYC and an A. D. White Professor-at-Large at Cornell University. From 2000 to 2007, he was at Columbia University, then at Yahoo! Research. He is the author of "Everything is Obvious (Once You Know the Answer): How Common Sense Fails Us" (Crown, 2011).