Behavioral science · mechanism
Complex contagion
Damon Centola, 2018
Some things spread on a single touch — a rumor, a virus, a meme. Others do not. Centola showed that costly or contested behaviors usually require multiple reinforcing exposures from people you trust before you will adopt them: one enthusiastic contact is not enough; you need to see several of your own cross the line first. That difference — simple versus complex contagion — changes which network structures actually move a behavior.
Working definition
Adoption requiring social reinforcement; wide-bridge network structures, not just many weak ties, carry costly or contested behaviors.
Where Vela uses this
Complex contagion is the spine of the network-mediated-adoption thesis that links Vela's behavioral-science lens to Mike's wider work on how change actually travels. It reframes adoption as a property of network structure and social reinforcement, not persuasion alone. It pairs with diffusion of innovations (the older sequence it refines) and the strength of weak ties (which it productively complicates — wide bridges, not just many weak ties, carry hard behaviors).
Origin & lineage
Granovetter's threshold models (1978) → Centola & Macy's formalization of complex contagion (2007) → Centola's experiments and *How Behavior Spreads* (2018) / *Change* (2021).
Where it shows up in Vela
Magazine
Library
Related concepts
- Diffusion of innovations
Reads against — Refines the classic diffusion model for behaviors that need reinforcement.
- The strength of weak ties
Reads against — Weak ties carry information; complex contagion needs strong, redundant ties.
Scholars
Honest framing
Which behaviors are genuinely 'complex,' and how far the network experiments generalize to messy real-world settings, are still being worked out. Vela uses the simple/complex distinction as a sharp tool, not as a finished map of adoption.