The dynamics of norm change in the cultural evolution of language

Significance Social conventions, such as shaking hands or dressing formally, allow us to coordinate smoothly and, once established, appear to be natural. But what happens when a new convention replaces an old one? This question has remained largely unanswered so far, due to the lack of suitable data. Here, we investigate the process of norm change by looking at 2,541 linguistic norm shifts occurring over the last two centuries in English and Spanish. We identify different patterns of norm adoption depending on whether the change is spontaneous or driven by a centralized institution, and we propose a simple model that reproduces all of the empirical observations. These results shed light on the cultural evolution of linguistic norms and human collective behavior. What happens when a new social convention replaces an old one? While the possible forces favoring norm change—such as institutions or committed activists—have been identified for a long time, little is known about how a population adopts a new convention, due to the difficulties of finding representative data. Here, we address this issue by looking at changes that occurred to 2,541 orthographic and lexical norms in English and Spanish through the analysis of a large corpora of books published between the years 1800 and 2008. We detect three markedly distinct patterns in the data, depending on whether the behavioral change results from the action of a formal institution, an informal authority, or a spontaneous process of unregulated evolution. We propose a simple evolutionary model able to capture all of the observed behaviors, and we show that it reproduces quantitatively the empirical data. This work identifies general mechanisms of norm change, and we anticipate that it will be of interest to researchers investigating the cultural evolution of language and, more broadly, human collective behavior.