The United Nations' support for indigenous cultural heritage preservation coexists with nationalist concerns about protecting national cultures from immigration. While cultures are constantly evolving, fears of cultural loss remain politically relevant. Most social science models of cultural change predict the impossibility of sustaining diverse cultural variants in structurally unequal, integrative societies – those that accept diversity but encourage mutually beneficial, though potentially unequal, interaction. This paper addresses the maintenance of cultural diversity in such societies. Cultural diversity is structured within groups that distinguish themselves based on cultural norms. At group boundaries, identity marking reduces miscoordination. History shows interactions among groups with unequal power, requiring cross-cultural competence (CCC) – the ability to interact successfully across cultural boundaries – to facilitate mutually beneficial engagement. CCC is prevalent but often ignored in cultural dynamics models, leading to the inaccurate prediction of cultural homogeneity. This paper uses data from an Amazonian ethnic boundary to develop a new theoretical model incorporating CCC to understand cultural sustainability.

Existing theoretical models of cultural change largely ignore cross-cultural competence (CCC), predicting that cultural diversity is unsustainable in structurally unequal, integrative societies. These models assume that individuals with different norms cannot coordinate effectively, leading to a perceived trade-off between cultural diversity and mutually beneficial inter-group interaction. Several models are discussed, including those focusing on constant minority influx, learning errors, valued group identity, limited inter-ethnic interaction due to group boundaries, social network structures, and complementary coordination. In all these models (except those with complementary coordination), the sustainability of cultural diversity relies on the limitation of inter-ethnic coordination, highlighting the perceived tradeoff between diversity and mutually beneficial interaction. This paper aims to demonstrate that this tradeoff is not inevitable.

The study utilizes data from Bunce (2020), which measured norms and CCC in a population of Matsigenka (minority) and Mestizos (majority) in Amazonian Peru. Participants indicated their preference for inheritance division norms (by need or evenly) and guessed the most common response in both in-groups and out-groups. Phenotypes were assigned based on personal preference and accuracy of group norm predictions: CCC (correct predictions) and UCC (uni-cultural competence, incorrect predictions). Bayesian item-response theory (IRT) models estimated phenotype frequencies. A new theoretical mathematical model incorporating CCC and inter-group interaction was constructed. The model includes a smaller group (S) and a larger group (L), initially preferring different norms (1 and 2 respectively). In each time step, individuals interact, receiving payoffs based on successful coordination (1) or miscoordination (0). CCC individuals always coordinate but incur costs (m for effort, c for cognitive dissonance). UCC individuals only coordinate with shared norms. Structural inequality is modeled (βs ≠ βl), with S members having lower bargaining power. Identity-based norm valuation (i) adds to payoffs. Individuals may change their phenotype based on anticipated payoffs (modeled as a logistic function), considering in-group interactions. Equations detailing payoff calculations and transitions between phenotypes are provided. A simplified model, assuming only CCC individuals in group S and UCC individuals in group L, reduces dynamics to a single difference equation.

The empirical data from the Matsigenka and Mestizos revealed a prevalence of CCC, particularly among individuals with inter-ethnic experiences. The theoretical model, informed by this data, showed that cultural diversity can be maintained even under conditions of structural inequality and intense inter-group interaction. The model demonstrated that a combination of CCC and strong identity-based valuation of the minority-typical norm is key to maintaining diversity. In the model, the identity valuation must outweigh the cognitive dissonance cost for minority CCC individuals coordinating with the out-group using their non-preferred norm. The results were largely robust to changes in model assumptions. A simplified model, focusing on transitions between CCC phenotypes in the minority group, illustrated how minority-typical norms could be sustained intergenerationally if parents' valuation of cultural identity (i) surpasses a threshold determined by learning costs (m) and cognitive dissonance cost (c). The model indicates that CCC can effectively insulate minority norm dynamics from group-level power differences.

The model suggests that fostering CCC within disempowered groups and strengthening the identity-based valuation of in-group norms are potential strategies for sustaining cultural diversity. Many disempowered groups already use these strategies, learning majority norms while developing identity-affirming institutions. This model offers an explanation for how learning majority norms can paradoxically complement these strategies to preserve cultural diversity. The model emphasizes that valuing minority norms and identity can be a characteristic of CCC individuals engaging with the majority within a multicultural society, replacing fear of cultural loss with confidence in its durability. This might ease the confrontation of inherent structural inequalities.

This paper presents a novel model showing that the tradeoff between cultural diversity and mutually beneficial inter-ethnic interaction is not inevitable. By incorporating cross-cultural competence and identity valuation, the model demonstrates the potential for stable mixed equilibria where cultural diversity is maintained despite structural inequality. Future research should explore modifications of the model, including reciprocal effects of CCC and identity valuation on inter-generational dynamics, non-random norm forgetting, evolving interaction preferences, social network structures, migration patterns, and more complex signaling mechanisms. Empirical studies should explore the wider range of CCC phenomena, like inequality within groups or strategic inter-group miscoordination.

The model relies on several simplifying assumptions, potentially limiting the generality of the results. Future work should explore modifications to incorporate more complex social dynamics, including reciprocal effects between CCC and identity valuation over generations, non-random forgetting, evolving interaction preferences, social network effects, migration, and complex signaling. The cross-sectional nature of the empirical data limits the ability to rigorously test the dynamic predictions of the model; longitudinal data is needed.