They illustrate this illusion with a theoretical example: a set of 14 nodes linked up to form a small world network, just like a real social network (see picture above). They then color three of these nodes and count how many of the remaining nodes link to them in a single step.
Two versions of this setup are shown above. In the left-hand example, the uncolored nodes see more than half of their neighbors as colored. In the right-hand example, this is not true for any of the uncolored nodes.
But here’s the thing: the structure of the network is the same in both cases. The only thing that changes is the nodes that are colored.
This is the majority illusion—the local impression that a specific attribute is common when the global truth is entirely different.
Via Gino Tocchetti