Complex Contagions and the Weakness of Long Ties

TLDR

Weak ties are long and connect socially distant locations, enabling rapid diffusion, but complex contagions require multiple sources of social affirmation, as seen in high‑risk social movements, avant‑garde fashions, and unproven technologies. The authors test whether the “strength of weak ties” generalizes from simple to complex contagions. The study finds that as adoption thresholds rise, long ties can hinder diffusion, and that complex contagions depend mainly on bridge width rather than length, with wide bridges common in spatial networks and partly explaining the spatial spread of social movements.

Abstract

The strength of weak ties is that they tend to be long—they connect socially distant locations, allowing information to diffuse rapidly. The authors test whether this "strength of weak ties" generalizes from simple to complex contagions. Complex contagions require social affirmation from multiple sources. Examples include the spread of high‐risk social movements, avant garde fashions, and unproven technologies. Results show that as adoption thresholds increase, long ties can impede diffusion. Complex contagions depend primarily on the width of the bridges across a network, not just their length. Wide bridges are a characteristic feature of many spatial networks, which may account in part for the widely observed tendency for social movements to diffuse spatially.