Have you ever found yourself staring at Facebook, blinking in disbelief because you can’t quite fathom why something is so popular? Well you might just be victim of a network quirk that makes it appear as though something is common—when in fact it’s actually rare.

A new piece of research from the University of Southern California reveals a new kind of naturally occurring illusion that means you may observe a feature—an opinion, say, or the adoption of a themed avatar—in most of your friends even though it’s actually quite rare across the entire network.


The researchers show visually how this can work using a simplified social network with just 14 members. Keeping the structure (that is, the links between members) of the network the same, they then color three members in red—that could be the particular feature we just mentioned—and then count how many members link to them in a single jump.

The example above shows that when different members are colored red—and remember that’s all that’s changing—the result vary dramatically. On the left example, all the uncolored members see over half of their acquaintances are colored red; on the right hand side, it doesn’t look that way to any of the uncolored members.

The team behind the research has dubbed this the majority illusion: the effect through which a local view suggests something is common when the truth across the entire network is that it’s actually rare. Technology Review points out that it rears its head when the attribute appears in the best-linked members—the ones with the most friends.


The researches also tested their theory, too, looking at Digg, networks of political blogs and, err, the coauthorship network of high-energy physicists to see if the effect could be observed in the wild. You can read the full investigation in their paper, but the overall answer is: yes, it can be.

It’s a neat finding, and could help explain why some content becomes so popular online. But it could also explain something a little darker, with the researchers pointing out that “under some conditions, even a minority opinion can appear to be extremely popular locally.” In other words, toxic yet niche views may sometimes appear to be more popular than they really are. At least, let’s hope so.

[arXiv via Technology Review]

Image by Chris Potter under Creative Commons license