In social interactions, human decision-making, attitudes, and beliefs about others (and hence social norms, shared expectations about what people in the group do and what they think should be done) coevolve. Here we attempt to disentangle some of this complexity by using an integrative mathematical modeling and a 35-day behavioral experiment.

Our model includes material payoffs in the utility function of each individual along with benefits from complying with the norm, from following one’s own beliefs, and from conforming to some external prescription.

To validate it, we utilize a Common-Pool Resources paradigm with messaging promoting group-beneficial behavior. We show that personal norms and conformity with expected peers’ actions have the largest impact on decision-making, while material benefits and normative expectations have smaller effects.

Messaging greatly decreases the weight of personal norms, simultaneously increasing the weight of conformity. It also markedly influences personal norms and normative expectations. Both cognitive and social factors are important in the dynamics of beliefs. Between-individual variation is present in all measured characteristics and notably impacts observed group behavior.

Those conclusions are further validated with a larger set of experiments with a different design, a different basic game (Collective Risk Dilemma), and a different population (Beijing).