An idea online can start as a small joke, rumor, or belief. At first, it’s easy to ignore. But with a little twist, it can spread fast and reach millions. Why do some ideas fade while others go viral?
A new study in Physical Review Letters offers an answer. Researchers from the University of Vermont and the Santa Fe Institute have built a new model for what they call “self-reinforcing cascades.” These are chains of events where the thing being shared—whether a meme, belief, or even a virus—changes as it spreads, and those changes can make it stronger.
Earlier models treated spreading as simple branching: one person tells two people, they each tell two more, and so on. But in those models, the idea or virus never changes. The new research shows that real-life spreading is more dynamic—things evolve along the way, and that evolution often makes them spread further.
Professor Sid Redner from SFI explains it with a forest fire analogy: fires burn more intensely through dense woods and weaken when crossing gaps. Ideas, jokes, and diseases behave the same way—they grow stronger or weaker depending on the context.
In this model, every time an idea spreads, it can either gain or lose strength. If it weakens too much, it dies. But if it gets even a little better, it can trigger a large cascade. This simple rule produced realistic patterns seen in viral events: most things die quickly, but a few explode unpredictably.
Lead author Laurent Hébert-Dufresne says past theories assumed the world was always balanced on a knife’s edge, ready to tip into virality. But this model shows you don’t need that assumption—variability happens naturally when what’s spreading can evolve.
Beyond theory, the findings could help scientists study how misinformation, beliefs, and social trends spread online.
Press release from Sante Fe Institute
