How Behaviour Spreads

On the basis of original experimental research, this book about the science of complex contagions gives the lie to parallels between the diffusion of viruses and that of beneficial behaviours and innovations. It shows that the 'weak ties' involving long distance connections linking acquaintances are not sufficient to spread behaviours, but rather stronger, more closely knit and densely overlapping networks are necessary, partly because of resistance to change and social inertia. Weak ties work for the spreading of information but not of behavioural change. Here we need reinforcement from multiple sources, paralleled in a highly effective campaign to increase contraception in Korean villages – neighbours supported each other in adopting new patterns of behaviour through social reinforcement. For those who do not already know each other, homophily generates empathy between participants facilitates the process - the research examples involve the health field. It is not surprising to learn that 'the most innovative, challenging and difficult behaviours require the greatest levels of social reinforcement.' (p. 178) This has extensive and profound implications for policy implementation or even nudges - we need to make use of strong existing ties and not simply rely on information diffusion through the Internet.