Human groups have long faced ecological threats such as resource stress and warfare, and must also overcome strains on coordination and cooperation that are imposed by growing social complexity. Tightness-looseness (TL) theory suggests that societies react to these challenges by becoming culturally tighter, with stronger norms and harsher punishment of deviant behaviour. TL theory further predicts that tightening is associated with downstream effects on social, political and religious institutions. Here, we comprehensively test TL theory in a sample of non-industrial societies. Since previous studies of TL theory have sampled contemporary countries and American states, our analysis allows us to examine whether the theory generalizes to societies in the ethnographic record and also to explore new correlates of tightness that vary more in non-industrial societies. We find that tightness covaries across domains of social norms, such as socialization, law and gender. We also show that tightness correlates with several theorized antecedents (ecological threat, complexity, residential homogeneity) and several theorized consequences (intergroup contact, political authoritarianism, moralizing religious beliefs). We integrate these findings into a holistic model of tightness in non-industrial societies and provide metrics that can be used by future studies on cultural tightness in the ethnographic record.
