Facial expressions in Manga (Japanese) comics. East Asian culture strongly regulates the expression of emotions, particularly in their impact on other people. (source)
Humans have had to adapt not only to physical environments (climate, vegetation, wildlife) but also to cultural environments (diet, language, codes of behavior, class and family structure, etc.). A culture will thus select for those mental predispositions and personality types that are most compatible with it.
This point is made by a recent paper on emotion regulation in East Asian and Western cultures:
Culture influences the development of psychological tendencies by presenting specific norms, practices, and institutions for how to act properly and be a good person […] culture is not only constrained by genetics but also influences the behavioral expression of genes and can thus moderate the psychological and behavioral expressions of genotypes. We propose that genes may affect phenotypic expression in the form of underlying psychological tendencies, but how and whether these tendencies are manifested in actual behavioral patterns may be shaped by sociocultural factors. (Kim et al, 2011)
The authors studied a gene that influences the way we regulate emotions. This is the oxytocin receptor gene OXTR rs53576, which has two alleles ‘A’ and ‘G’. The GG genotype is associated with more sensitive parenting, greater sensitivity to infant crying, greater empathy, less loneliness, and a more prosocial temperament. These tendencies are less characteristic of the AA genotype, and the AG genotype produces outcomes that fall between the two.
The ‘A’ allele is more common among Koreans than among white Americans, perhaps because its negative effects are buffered by a culture that fosters empathy, specifically a keen interest in the possible adverse effects of one’s behavior on others:
[…] in more collectivistic cultures, the expression of emotions is practiced with concern for negatively affecting social relations, whereas in more individualistic cultures, the expression of thoughts and feelings is valued as a sign of an independent self (Kim et al., 2011)
A more individualistic culture, like the one that prevails in the U.S., would thus have a weaker capacity to offset the negative effects of the AA genotype.
Interestingly, culture also influences expression of the GG genotype, but in a different way. Because people with this genotype tend to be more attuned to rules of correct behavior, they’re more likely, in an American context, to express their emotions than are people with the AA genotype, apparently because white American culture today values the expression of emotions. Koreans, however, show the opposite pattern:
Emotional suppression was most clearly observable among Koreans with the OXTR GG genotype, those characterized as more socioemotionally sensitive, compared to those with AA genotype. Among Americans, the pattern was reversed, such that those with the GG genotype engaged in less emotional suppression, compared to those with the AA genotype. (Kim et al., 2011)
This is actually the reverse of the Baldwin effect. If white American culture exercises less control over emotions, particularly in their possible adverse effects on others, there should correspondingly be weaker genetic control. The same selection pressure should have produced similar cultural and genetic outcomes. Yet, paradoxically, the actual outcomes are almost poles apart. Although white Americans are less softwired for empathy and control of emotions, they seem to be more hardwired in this respect.
Of course, if we were to go back a hundred years, we would see that white Americans differed less, in this same respect, from East Asians. When I look at old family photos, I notice that the subjects never smiled for the camera. It was considered rude to smile at strangers, who might have taken such behavior the wrong way. Now smiling is normal, even mandatory. A century ago, white Americans controlled their emotions much more than they do now, especially with a view to minimizing their impact on other people.
There is another possible answer to the above paradox. Maybe weaker cultural control led to stronger genetic control, partly as a kind of compensatory action and partly because a less kin-based society requires more hardwiring of empathy. As Alan Macfarlane has argued in The Origins of English Individualism (and also hbd* chick), the English began to enter a freer and more individualistic cultural environment as far back as the 13th century (see earlier post). Because most social and economic relationships were no longer with close kin, it became necessary to extend the feelings of empathy one felt for immediate blood relations to a much larger circle of people. This psychological substrate would later make possible the rise of a market economy, i.e., the replacement of kinship by the market as the main organizing principle of society.
References
Kim, H.S., D.K. Sherman, T. Mojaverian, J.Y. Sasaki, J. Park, E.M. Suh, & S.E. Taylor. (2011). Gene–Culture Interaction: Oxytocin Receptor Polymorphism (OXTR) and Emotion Regulation, Social Psychological and Personality Science, 2, 665-672
http://taylorlab.psych.ucla.edu/2011_Gene-Culture%20Interaction_OXTR%20and%20Emotion%20Regulation.pdfMacfarlane, A. (1978a). The origins of English individualism: Some surprises, Theory and society: renewal and critique in social theory, 6, 255-277.
http://www.alanmacfarlane.com/TEXTS/Origins_HI.pdfMacfarlane, A. (1978b). The Origins of English Individualism: The Family, Property and Social Transition, Oxford: Blackwell.