‘The idea is a simple one: successful social change is not about information; it’s about norms. Social networks are not merely the pipes through which ideas and behaviours flow. They are also prisms that determine how we see those behaviours and interpret those ideas’

Change: How to Make Big Things Happen, by Damon Centola, 2021

“Through the hidden power of social influence, the network around us shapes how we respond to an innovation, causing us either to ignore it or to adopt it. This much deeper process of social spreading is called complex contagion, and it has given rise to a new science for understanding how change happens—and how we can help make it happen.”


This book is fascinating. It’s written by an academic who has interests in how, in an age of social networks, ideas and behaviours spread. The basic premise is that information and disease spread as “simple contagions”, requiring only one contact for transmission, while behaviours typically spread as “complex contagions”, requiring multiple sources of reinforcement to induce adoption.

A great feature of the book is the way research mixes smoothly with extended case studies and quirky examples. Successes – like Korea’s birth control initiative – are balanced with surprising failures, like Google Glass. There are valuable detailed explanations of the emergence of causes like #BlackLivesMatter. Then there are the eccentric case studies: the Dvorak keyboard, VHS and Betamax, the British Army Pals regiments of WW1, the ice-bucket challenge, and the Aerosmith gesture. It’s whacky, fascinating, and persuasive all at once. 

So What? 

The subtitle gives the answer. The book lays out thinking for a networked age to make big things happen. Most of the big things we pursue are complex contagions, involving risk. The higher the risk the more we need the ‘proof’ of others, the difference between being aware of an innovation and being convinced to adopt it. The geometry of the network dictates the change. Weak ties have a geometry which looks like a firework display with connections reaching out randomly from the centre quickly but then fading out. Strong ties, needed for influence and ‘entrenched’ change looks like a fishing net with clusters which are more tightly connected. For big change you need the fishing net.

Now What?

If you are involved in any way with the use of social media to promote a product, an idea, an experience, or a cause then this book is a must. Many of your strategies will be throwing money away. To make your change initiative successful, do not rely on the contagious spread of information to solve the problem, don’t invest in personality endorsements, invest instead in sub-groups with whom you are loosely connected. Clustering change agents together can lower the size of the critical mass needed to trigger social change. Work out the barriers to adoption. Is it an issue of credibility, legitimacy, or excitement? Once you identify the kind of resistance, you will also know how to create relevance.

 Ideas and beliefs that reinforce existing biases spread easily in centralized networks. Innovative ideas that challenge our biases and improve our thinking benefit from a contagion infrastructure that protects innovators from too many countervailing influences and offers wide bridges to convey innovative ideas.”

Worth a read, then a re-read.