Connected: The Amazing Power of Social Networks and How They Shape Our Lives by Nicholas Christakis and James Fowler
Fowler used the very detailed data it collected – including information on people’s family and friendship ties, their diet, lifestyle and sense of wellbeing – to demonstrate that behaviours and moods tend to spread through a population on the model of a contagion. They showed in particular (using computer programmes that allow them to construct “network maps”) that different behaviours and moods, much like different viruses, spread according to different patterns.
.. While eating and smoking habits can be transmitted across long-distance networks, the transmission of happiness tends to require face-to-face contact.
.. If people start or stop smoking in groups, or mugging spreads like a virus through a city, then group-based approaches to tackling these problems are likely to be more effective than ones focused on individuals – or on the “community” as a whole.