The Rules of Contagion

these individuals won’t necessarily pass it on much further. Then
there’s the structure of our interactions. Whereas financial networks
are ‘disassortative’ – with big banks connected to lots of small ones –
human social networks tend to be the opposite. From village
communities to Facebook friendships, there’s evidence that popular
people often form social groups with other popular people.[9] It
means that if we target a few popular individuals, we might get a
word-of-mouth outbreak that spreads quickly, but it probably won’t
reach much of the network. Sparking multiple outbreaks across a
network may therefore be more effective than trying to identify high
profile influencers within a community.[10]
Watts has noticed that people tend to mix up the different
influencer theories. They might claim to have found hidden
influencers – like the merchant in Milgram’s experiment – and used
them to make something spread. But in reality they may have just run
a mass-media campaign or paid celebrities to promote the product
online, in effect bypassing word-of-mouth transmission altogether.
‘People either carelessly or deliberately conflate them, to make the
boring thing sound like the interesting thing,’ Watts said.
The debate around influencers shows we need to think about how
we are exposed to information online. Why do we adopt some ideas
but not others? One reason is competition: opinions, news, and
products are all fighting for our attention. A similar effect occurs with
biological contagion. The pathogens behind diseases like flu and
malaria are actually made up of multiple strains, which continuously
compete for susceptible humans. Why doesn’t one strain end up
dominating everywhere? Our social behaviour probably has
something to do with it. If people gather into distinct tight-knit cliques,
it can allow a wider range of strains to linger in a population. In
essence, each strain can find its own home territory, without having to
constantly compete with others.[11] Such social interactions would
also explain the huge diversity in ideas and opinions online. From
political stances to conspiracy theories, social media communities
frequently cluster around similar worldviews.[12] This creates the
potential for ‘echo chambers’, in which people rarely hear views that
contradict their own.