Ancestral Diversity: A Socioecological Account of Emotion Culture

Abstract

Cultural differences in emotion expression, experience, and regulation can cause misunderstandings with lasting effects on interpersonal, intergroup, and international relations. A full account of the factors responsible for the emergence of different cultures of emotion is therefore urgent. Here we propose that the ancestral diversity of regions of the world, determined by colonization and sometimes forced migration of humans over centuries, explains significant variation in cultures of emotion. We review findings that relate the ancestral diversity of the world’s countries to present-day differences in display rules for emotional expression, the clarity of expressions, and the use of specific facial expressions such as the smile. Results replicate at the level of the states of the United States, which also vary in ancestral diversity. Further, we suggest that historically diverse contexts provide opportunities for individuals to exercise physiological processes that support emotion regulation, resulting in average regional differences in cardiac vagal tone. We conclude that conditions created by the long-term commingling of the world’s people have predictable effects on the evolution of emotion cultures and provide a roadmap for future research to analyze causation and isolate mechanisms linking ancestral diversity to emotion.

Imagine you are Ella Fosse, a young girl from a small town in Norway. You have just arrived alone at Ellis Island, New York, after learning your first English word: “seagull.” You enter the Great Hall and are met by a throng of unfamiliar faces, styles of dress, demeanors, and skin tones that you have never encountered in your short lifetime (see Figure 1 for an illustration of the variety of people who arrived at Ellis Island during an active period of emigration to the United States). You “tried to find somebody that would speak Norwegian,” but could not (Fosse & Dallett, 2004). Ella Fosse immigrated from Norway in 1922 and was one of many to come from a culturally homogenous place to the most culturally diverse city in the world, and her story is one of confusion on all sides, though it is far from uncommon. By the 1920s, millions of immigrants had entered the United States through Ellis Island and New York was over 36% foreign-born (“Total and Foreign-Born Population: New York Metropolitan Region by Subregion and County, 1900–2000,” 2004). Here we propose that the solutions to social challenges posed by living in contexts of variability of language of origin and emotion norms over long timescales systemically influence the evolution of emotion culture—that is, the solutions to these social challenges shape the norms and practices for the expression, experience, and regulation of emotions in context.

Figure 1.

Immigrant photos taken at Ellis Island in the early 20^th century from Top (left to right): Algeria, Greece, and Russia and Bottom (left to right): Guadeloupe, Albania, and the Netherlands (Mesenhöller & Sherman, 2005). The thousands of immigrants that came through this port every day were as foreign in all regards to each other as they were to the Americans who welcomed them.

In the following sections, we 1) introduce the socioecological approach to understanding human behavior (Henrich & McElreath, 2003) and define the socioecological factor of interest here: ancestral diversity, 2) summarize findings linking ancestral diversity to cultures of emotion, and 3) report data on the physiological implications of life in ancestrally diverse regions. We conclude with suggestions for future research directions.

Socioecological Approaches to Culture

Culture is the expression of beliefs and values in a society’s institutions, practices, and artifacts that is transmitted across generations through social learning (Oishi, 2014). Socioecological approaches hold that culture codifies and transmits successful solutions to the challenges and opportunities afforded by the physical and social environment (Sng et al., 2018).

For example, the flood-prone conditions of Eastern Africa have historically made for a very unstable ecology for people of the Maasai tribes. In response to these conditions, the Maasai developed practices that disperse risk such as establishing culturally enforced relationships (“osotua”) that transfer resources based on need with no expectation of repayment (Hao et al., 2015).

Ancestral diversity is a socioecological feature of human environments that represents the migratory history of a region over centuries. It refers to the fact that the present-day populations of some regions of the world (e.g., Norway and Japan) descended over a long timescale largely from ancestors of the same region, while other present-day populations descended from ancestors of many regions (e.g., Australia, The Caribbean, and the United States). Critically, the co-mingling of people from many regions of the world over centuries may disrupt cultural norms of origin and add complexity to communication styles, thus making ancestrally diverse environments particularly ripe for cultural evolution.

The World Migration Matrix summarizes both forced and unforced human migration to and from present-day countries from 1500CE to 2000 and quantifies ancestral diversity as the number of source countries that contributed to the present-day population of every other country over a period of 500 years (Putterman and Weil, 2010; Figure 2a).¹ The matrix takes account of the fact that present-day country borders and names have changed over history. It thus provides a readily interpretable metric for research on ancestral diversity. More recently, using information from the United States Census, researchers have also quantified the ancestral diversity of the states of the United States (Niedenthal et al., 2018; Figure 2b).

Figure 2. Country- and US State-Level Ancestral Diversity.

(A) depicts the ancestral diversity of the countries of the world (from Putterman & Weil, 2010) and (B) depicts the ancestral diversity of the states of the United States (Niedenthal et al., 2018), both in the year 2010. Higher ancestral diversity is represented by darker colors.

Contexts of high ancestral diversity pose challenges and opportunities that differ substantially from contexts of low ancestral diversity. Life in ancestrally diverse, relative to more homogeneous, environments would likely have been marked by low socio-emotional predictability, and required the establishment of new social norms, emotion expression practices, and multi-cultural institutions that propagate through cultural learning. Negotiations between individuals and groups who lacked a common language and shared social norms would have taken place repeatedly over time, generating novel communication norms. Specifically, interactions in contexts of social unpredictability would be made smoother if people made their intentions and values explicit in easily recognizable nonverbal displays, such as transparent and relatively large expressions, such as smiles or scowls, to clearly delineate inter-group dynamics (Oishi et al., 2009). Indeed, translation not only of language but of intent is one of the oldest professions in the world, dating as far back as the ancient Babylonians (Sayce, 1922). The establishment of new communication norms, expressive practices, and the institutions that support them would be refined and propagated through cultural learning to modern cultures of emotion. In the next section, we review findings that document the existence of such adaptations.

Ancestral Diversity and Emotion Expression

Display Rules.

There are vast cross-cultural differences in norms concerning the degree to which emotions should be explicitly displayed to others, and if so, to whom (Matsumoto et al., 2008). Rychlowska and colleagues (2015) conducted secondary analyses of reports of emotion display rules from 5,361 respondents from 32 countries (Matsumoto et al., 2008). Consistent with the theorized historic need to communicate nonverbally, respondents from high ancestrally diverse countries favored the overt expression of both negative and positive emotions while those from low ancestrally diverse countries favored the suppression of emotional expression (Rychlowska et al., 2015). This effect persisted even when analyses controlled for other factors that may explain emotional expressiveness, such as GDP, population density, individualism, and residential mobility. Importantly, indicators of present-day diversity such as measures of ethnic fractionalization did not account for significant variance in display rules, suggesting that emotion practices and norms evolve over relatively long timescales.

Recognizability of Emotional Expression.

If display rules dictate the expression rather than suppression of emotion, it would also make sense that the resulting expression be easily interpreted by people from vastly different backgrounds. Wood and colleagues (2016) tested the hypothesis that expressions of emotion made by residents of countries of high ancestral diversity are more accurately recognized cross-culturally than are expressions displayed by people from countries of low ancestral diversity. The researchers analyzed data from 92 published studies in which participants from one country labeled the facial, bodily, and/or vocal expressions of a variety of different emotions displayed by people from another country (Wood et al., 2016). As predicted, residents of ancestrally diverse countries expressed emotions, both positive and negative, in ways that were more accurately recognized by residents of other countries. This would be a critical adaptation for those in diverse regions to avoid unnecessary information disruption caused by emotional miscommunications.

Smiling Behavior.

The daily tasks that are more frequent in regions of high ancestral diversity include successfully moving into and out of new social groups and creating opportunities for cooperation with relative strangers. When people smile, they signal trustworthiness (Todorov et al., 2009) and openness to cooperation (Manzini et al., 2009; Schug et al., 2010), but the frequency of smiling across countries varies enormously. For example, smiling is less frequent in Russia than in England or the United States (Arapova, 2016).

Girard and McDuff (2017) reasoned that the need to develop trust in strangers would be higher in countries of high compared to low ancestral diversity and that this factor could explain variations in the frequency of smiles across countries. They analyzed spontaneous smiling by 866,726 individuals from 31 countries while those individuals watched interesting advertisements. When controlling for other predictors of smiling such as affluence, population density, urbanization, and ethnic fractionalization, individuals from countries of high ancestral diversity smiled about twice as frequently as individuals from countries of low ancestral diversity.

The same effect was conceptually replicated in analyses of the frequency of smiling and laughter from the 2017 Gallup World Poll, which sampled nearly 149,000 adults in 142 countries (Niedenthal et al., 2018). After controlling for GDP and present-day diversity, the authors found that ancestral diversity significantly predicted smiling and laughter on the previous day (Figure 3). Niedenthal and colleagues (2018) found the same result within the U.S. such that residents of more ancestrally diverse states (see Figure 2, panel B) were also more likely than those from less ancestrally diverse states to report having smiled and laughed on the previous day.

Figure 3. Smiling, laughter, and ancestral diversity of countries of the world.

Ancestral diversity scores in log-transformed units. Regression lines control for GDP and ethnic fractionalization (Niedenthal et al., 2018).

Ancestral Diversity and Arousal Control

Thus far, we have provided support for the idea that emotion cultures differ importantly as a function of ancestral diversity. However, living in an emotion culture in which norms for nonverbal communication dictate a) emotional expressiveness, b) the production of easily interpreted emotion expressions, and c) the frequent use of smiles to create new alliances does involve repeated experiences of high arousal (Blascovich et al., 2001; Mendes et al., 2002) that require regulation for successful social interaction (Richeson & Shelton, 2007).

The balance between one’s sympathetic arousal and parasympathetic nervous system activity constitutes one basis of the regulation of arousal. And the quality of this balance is indicated by an individual’s vagal tone, indexed by baseline heart rate variability (HRV). Because of its link to context-appropriate, flexible regulation of arousal, vagal tone is theoretically a physiological indicator of capacity for effective social engagement (Porges, 2007). Evidence suggests that practicing the regulation of arousal appropriately for the situation, reliably improves vagal tone (Butler, Wilhelm, & Gross, 2006; Thayer & Koenig, 2019). As the findings so far reviewed indicate, the practices that come to define cultures of emotion in high ancestral diversity regions create a condition in which vagal control is practiced repeatedly. Thus, Harrod and colleagues (2022) reasoned that, over individual lifetimes, people living in regions of high ancestral diversity develop, on average, better vagal control than individuals living in regions that are lower in ancestral diversity. To test the idea, Harrod and colleagues examined state-level baseline HRV data from 46 states of the United States. They found that residents of more ancestrally diverse states (e.g., Illinois) indeed had significantly higher baseline HRV compared to those from less diverse states (e.g., Alabama). The relationship held when controlling for indicators of individual health (e.g., BMI, sex, and cardiac health), a composite of state-level indicators of public health, and present-day population diversity of the states.

In a theoretically related study, Hampton and colleagues found that people from ancestrally diverse countries, namely participants from the United States and Mexico, showed increased regulatory neural responses to emotional images without explicit directions, whereas those from ancestrally homogenous backgrounds, namely Chinese participants, did not show such regulatory responses (Hampton et al., 2019; Varnum & Hampton, 2017). These findings suggest that living in ancestrally diverse regions where individuals have comingled across centuries in some capacity with those who do not share one’s language or customs, leads to a greater ability to regulate emotional arousal in putatively “safe” but arousing situations. Conversely, amplifying emotional arousal is not necessary to communicate complex emotions within a homogenous cultural context.

To summarize, cultures that emerge from regions of high versus low ancestral diversity represent distinct social contexts. The practices and norms (that represent solutions to navigating the former contexts) involve flexible responses to: 1) evolutionarily challenging stimuli and 2) interactions that require effective control over sympathetic arousal to permit engagement with individuals from different cultural backgrounds from oneself. Although future research is required to assess causality, it appears that exercising control over arousal may have reliable effects on human physiology over individual lifetimes.

Limitations and Future Directions

We have reviewed a series of correlational studies relating ancestral diversity to the emergence of distinct cultures of emotion. This is a relatively new area of research, and as of yet, few studies have implemented manipulations of ancestral diversity that allow for causal conclusions about the role of this socioecological factor in determining emotion culture. It could be, for example, that people who are most likely to migrate to and remain in ancestrally diverse places are naturally expressive and open to using explicit displays of emotion to establish cooperation and new social bonds. Future research will need to manipulate theoretically important characteristics of ancestrally diverse versus less ancestrally diverse contexts with the aim of evaluating the causal impact of those characteristics on the evolution of emotion culture.

One recent study attempted to fill the need for experimental research by examining the tendency to express and synchronize emotion expressions during cooperative social tasks. According to assigned condition, participants—who were not selected on the basis of cultural background—were permitted to or prevented from using spoken language to communicate during the study. The “no speaking” condition models one feature of life in regions of extensive historical migration, namely the initial lack of common language (Zhao, Wood, Mutlu & Niedenthal, 2022). Participants working in pairs took turns completing four tasks. On two of the tasks, specifically designed to elicit emotion during cooperation, participants tried to earn points that were allocated to the dyad. As expected, participant pairs assigned to cooperate without using spoken language were more facially expressive and their expressions became more synchronous than were paired participants who were permitted to communicate with spoken language. The findings suggest that expressiveness and the call-and-response synchronization of expressions increases with the need to communicate and cooperate nonverbally. Future studies should zoom in on additional characteristics that distinguish ancestrally diverse contexts from contexts of less ancestral diversity to evaluate their causal influence on emotion processes and the evolution of emotion culture more generally.

A second, related limitation of the research reviewed here is that correlations can arise for many reasons, one of which is the presence of third variables. It could be that cultures that arise in ancestrally diverse and less diverse regions differ in ways other than long history population heterogeneity and that these other factors explain the emergence of emotion cultures that favor transparent nonverbal displays of emotion and the use of smiles to establish trust and cooperation. All studies of ancestral diversity have controlled for many theoretically and empirically likely third variables. For example, Huff and colleagues (2021) conducted secondary analyses of Peace Corps volunteers’ adaptation to 55 different countries. Findings revealed that, when controlling for economic prosperity of the host country, adaptation was more successful as the ancestral diversity of the host country increased. A second study of students at an international business school replicated and extended the finding: even when accounting for many personality and demographic features of the students as well as economic features of the home and host countries, students adapted more readily to host countries with high compared to low ancestral diversity.

In another study, Shrira (2020) investigated the hypothesis that ancestral diversity is associated with lower prejudice towards outgroup members. The hypothesis was derived from principles of Contact Theory (2020), which holds that repeated interaction with outgroup members decreases prejudice. Contrarily, Group Threat Theory (Morris et al., 2011) holds that initial instances of contact, such as those experienced when immigrants arrive to a region that is host to recent (but not long-history) migration, trigger threat responses due to fear of competition for resources or the potential for undesired cultural shifts. The two theories thus make different predictions about outgroup prejudice as a function of prolonged contact (i.e., ancestral diversity) compared to recent contact (i.e., present-day diversity). Shrira (2020) analyzed responses to the World Values Survey across 90 countries and from the International Social Survey Program with participants from 31 countries. While controlling for GDP, a democracy index, and ecological stress, analyses found that ancestral diversity was inversely associated with outgroup prejudice, as expected by Contact Theory. Present-day diversity was associated with higher outgroup prejudice, consistent with Group Threat Theory, in one of the two studies.

Finally, as mentioned earlier in the paper, large-scale studies have also controlled for other plausible third variables including urbanization, individualism, population density, ethnic fractionalization, number of recent source countries to a country or state, social mobility, individualism-collectivism, and so on (e.g., Girard & McDuff, 2017; Rychlowska et al., 2015). It should be noted that the number of countries (or states) used to represent the theoretical construct of ancestral diversity, as well as the number of control variables tested in associated models, far exceeds the number of countries typically used to study other culture dimensions such as individualism (i.e., often two countries are examined, one assumed to represent high and the other low individualism based on past and potentially out-of-date indicators). Studies that focus on just two countries often fail to control for other variables that could produce the differences across the two examples of the cultural dimension of interest, even though two countries differ in potentially hundreds of ways other than the single culture variable.

We also recognize that cultural variation in how and when people experience, express, and regulate their emotions is accounted for by more than a single factor. This is not so much a limitation of the findings reviewed here as an invitation for researchers to identify additional, robust determinants of emotion culture. For example, Montequieu, a French philosopher, famously related emotional expressivity to climate and argued that residents of warmer climates were more emotionally expressive than residents of cooler climates. And subsequent tests of Montequieu’s hypothesis found support for his claim (Pennebaker, Rimé, & Blankenship, 1996). But the value of the present socioecological account remains. Understanding processes of emotion as they are determined by measurable socioecological factors is a powerful and generative approach that is amenable to exciting methodological applications and promises to produce profound insights into the meaning of culture.