From preference to dominance: The reinforcing and regressing effects of social influence

When adopting a behaviour, humans often rely on social information and are more likely to copy behaviours that are demonstrated by many other individuals. Despite numerous empirical demonstrations of such effects, the literature on social influence in binary choice remains disjoint, and there is a lack of a unifying framework for mapping the micro- and macro-level consequences of social influence. We propose a parsimonious and interpretable mathematical model of social influence and use it to reanalyse 294,703 choices by 20,480 individuals from an exhaustive collection of experiments on binary choice under social-influence. In addition, we define two new metrics that predict the possible macro-level consequences of social influence: 'preference amplification,' expressing the reinforcement of the dominant behaviour, and 'reversal potential' expressing the degree of bistability in the system, and the propensity of the inferior option to prevail. We show that in almost all experiments, social influence can lead to substantial amplification of the dominant preferences, whereas bistability appears to be possible in a subset of settings. Our approach can be used to contrast old and new work on social influence and to better understand the reinforcing or regressing effects of behaviour change interventions.