Science 360, 1116–1119 (2018)

Models of emergent phenomena in human populations have become a familiar sight in the physics literature. Calibration of and motivation for these models typically has to come from social science, ideally in the form of quantitative studies such as the one of Damon Centola and colleagues, who explored at which size a committed minority group can successfully shift social norms.

Empirical estimates for the critical mass needed to overturn established behaviour — for example, linguistic or gender conventions — range from 10% to 40% of the total population. Centola and co-workers examined these tipping points in the well-controlled setting of an online experiment.

They assigned 194 participants to groups of different sizes. The players then had to agree on names for pictured objects. In this scenario, a relatively sharp ‘phase transition’ emerged: once a minority group comprised more than 25% of all participants, they managed — stimulated by financial incentives — to establish a new equilibrium in which their choice was widely accepted. That percentage is unlikely to be universal, but a valuable benchmark for future studies, in particular those of online networks.