The experiment showed that messages don’t need highly connected people to get to a specific destination. But what if we’re interested simply in making something spread as far as possible? Could people who are more connected in the network – like celebrities – help ensure it takes off? A few years after the e-mail analysis, Watts and his colleagues looked at how web links propagate on Twitter. The results suggested that content was more likely to spread widely if it was posted by a person with lots of followers or a history of making things take off. Yet it was no guarantee: most of the time these people weren’t successful at creating large outbreaks.[6]
Which brings us to the more basic version of the influencer hypothesis. This is simply the idea that some people can be more influential than others. There is plenty of evidence to support this. For example, in 2012 Sinan Aral and Dylan Walker studied how a person’s friends influenced their choice of apps on Facebook. They found that within friendship pairings, women influenced men at a 45 per cent higher rate than they influenced other women, and over-30s were 50 per cent more influential than under-18s. They also showed that women were less susceptible to influence than men and married people were less susceptible than singles.[7]
If we want an idea to spread, we ideally need people to be both highly susceptible and highly influential. But Aral and Walker found that such people were very rare. ‘Highly influential individuals tend not to be susceptible, highly susceptible individuals tend not to be influential, and almost no one is both highly influential and highly susceptible to influence,’ they noted. So what effect could targeting influential people have? In a follow-up study, Aral’s team simulated what would happen if the best possible people were chosen to spark a social outbreak. Compared with choosing randomly, the pair found that picking targets effectively could potentially help things spread up to twice as far. It’s an improvement, but it’s a long way from having a few little-known influencers who can spark a huge outbreak all by themselves.[8]
Why is it so hard to get ideas to spread from person to person? One reason is that issue of people rarely being both susceptible and influential. If someone spreads an idea to lots of susceptible people, 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.
One of the most vocal online communities is the anti-vaccination movement. Members often congregate around the popular, but baseless, claim that the measles-mumps-rubella (MMR) vaccine causes autism. The rumours started in 1998 with a scientific paper – since discredited and retracted – led by Andrew Wakefield, who was later struck off the UK medical register. Unfortunately, the British media picked up on Wakefield’s claims and amplified them.[13] This led to a decline in MMR vaccination, followed by several large outbreaks of measles years later, when unvaccinated children
