Change, by Damon Centola
Why the most important variable in public affairs isn’t the message, but the structure through which it travels.
Masters in Public Affairs goes back to the foundational books in this field and extracts the principles that the best practitioners return to again and again. One book at a time.
“Successful social change is not about information. It’s about norms.”
— Damon Centola, Change
That sentence sits at the centre of one of the most important books I’ve read in the past decade. And it took me a while to fully absorb what it means.
We spend enormous energy in public affairs on information. Crafting the right message. Finding the right frame. Deploying the right spokesperson. Getting the word out. And all of that matters. But Damon Centola, a network scientist at the University of Pennsylvania, spent two decades running experiments that show the same thing over and over: getting the word out is the easy part. The hard part is getting people to act on it. And those are two completely different problems that require completely different approaches.
Here’s the distinction. Information spreads through casual contact. One person tells another who tells another. Centola calls this a simple contagion. News, gossip, awareness — one exposure is enough. You hear it, you know it, done.
But behaviour change — adopting a new technology, joining a coalition, supporting a policy, showing up at a protest — is what Centola calls a complex contagion. And complex contagions don’t spread through reach. They spread through reinforcement. People need to see multiple others in their network adopting before they’ll move. Not one influencer. Not one compelling message. Multiple independent sources, all pointing in the same direction.
That one distinction — simple vs. complex contagion — reframes almost everything we do. It means the viral model is wrong for the work that matters most. It means the influencer playbook is structurally flawed. It means awareness campaigns can actually backfire if they create visibility without adoption. And it means the most important variable in any change effort isn’t the quality of the argument. It’s the architecture of the network through which that argument travels.
That’s what this episode is about.
Why This Book Matters
I’ve been in public affairs for over 20 years. I’ve designed campaigns, built coalitions, run grassroots mobilisation efforts. And I’ve operated, like most of us, on a set of assumptions borrowed from marketing and epidemiology: maximise reach, find the influencers, make the message sticky.
Centola’s work challenges those assumptions head on. It shows, with controlled experiments, that they lead us to do the opposite of what works for complex change.
A few examples from the book that stuck with me:
Hybrid corn in Iowa was objectively superior to what farmers had, free to try, and desperately needed as the Dust Bowl approached. After years of aggressive marketing, adoption sat at 1%. The marketing itself strengthened the rumours working against it.
PrEP in Zimbabwe — a free daily pill that eliminates HIV transmission — was so ineffective that villagers who told doctors they were taking it had no traces in their bloodstream. Social stigma was more powerful than the fear of death.
Google Glass had a billion-user company behind it and massive awareness. But the visible gap between early adopters (Silicon Valley techies) and everyone else created resentment, not aspiration. The norm turned against the product.
In each case, the failure wasn’t in the message or the product. It was in ignoring the social network that would interpret it.
What We Cover in the Episode
This is a long episode — and intentionally so. There’s a lot of ground to cover and I wanted to do it properly. Here’s what we get into:
The core distinction between simple and complex contagions, and why it matters for everything we do in public affairs.
Fireworks networks vs. fishing net networks — why redundancy, not reach, drives adoption. And the finding that “laggards” who need multiple sources of reinforcement before adopting are 300 times more likely to stick than early adopters.
Countervailing influences — why targeting the most connected, most senior people first is often backwards. A person with 500 contacts is roughly 10 times less likely to adopt than someone with 50, because the silent non-adoption of the majority drowns out the signal from the few.
The 25% tipping point — Centola’s experimental proof that a committed minority of 25% can overturn an established norm, and why activism below that threshold looks like failure even when it’s accumulating toward a breakthrough.
Three principles of relevance — when to use similarity (credibility and solidarity) and when to use diversity (legitimacy). Most of us default to similarity. When the barrier is legitimacy, that default hurts us.
The polarisation experiment — where removing decorative party graphics from a screen was the only difference between zero learning and 90% accuracy among Democrats and Republicans looking at the same NASA data.
China’s 50 Cent party — how every mechanism for creating social change can be run in reverse to prevent it. The dark mirror of the entire framework.
And the mastery lesson: diagnose the infrastructure before you design the campaign.
Listen and subscribe here:
Bonus: Four Ideas From the Book That Didn’t Make the Episode
I took a lot of highlights while reading this book. More than I could fit into even a long episode. Here are four ideas that didn’t make the cut but are worth your time.
1. Stigma as a Resource
In the 1990s, public health campaigns were failing to reduce HIV transmission among injection drug users. The problem was familiar — drug users didn’t trust mainstream healthcare providers and weren’t interested in advice from authority figures.
