Research in social sciences, and especially in sociology and economics, aims to bring out general rules by studying the behavior and psychology of entire populations. In his book The Weirdest people in the world , Joseph Henrich shows that this research was in fact largely conducted by Western researchers on Western people. However, when we observe the different ways of thinking around the globe, Western, Educated, Industrialized, Rich and Democratic (WEIRD) people are characterized by very particular ways of thinking.
WEIRD people are highly individualistic, self-obsessed, control-oriented, nonconformist and analytical. They reason through universal categories and rules, are patient and hardworking, stick to impartial rules and principles and are often racked with guilt (rather than shame as for most non-WEIRD people).
To define themselves, WEIRD people focus on their personal attributes and achievements over their role, responsibilities and relationships.
Setting up a WEIRD vs non-WEIRD dichotomy is not meaningful, as global psychological variations are both continuous and multidimensional. What is important to understand is that looking at a wide range of psychological characteristics, WEIRD people lie at the extreme of the world distribution. The opposite extreme consists in kin-based institutions, which refer to societies where behavior is highly constrained by context and the type of relationship involved.
In this book, Joseph Henrich asks the question: how have these differences developed over time ?
Human beings are a cultural species, with a psychology specialized in acquiring information and behaviors from others. As a result of this process, known as cultural evolution, human norms are assembled into institutions. However, this process takes so much time that it is often not perceivable by human beings.
Cultural evolution has led to the creation of norms aimed at fostering cooperation between people, such as kin altruism, pair-bonding and incest aversion, which constitute some persistent institutions. Inversely, institutions can shape human brains through facultative effects (altering perceptions and judgments at a certain moment), cultural learnings and direct experience (adapting to incentives create by institutions, to have social recognition for example) and development impact (childhood and adolescence are periods of intense brain development, when life experiences can have strong impacts on our psychology).
The evolution of human societies can be traced back through this process. At the dawn of agriculture, all institutions were rooted in kin-based relationships. But, to scale-up, additional non-kin-based relationships had to be developed, especially to secure one’s land. Individually, agriculture was not better for people (people got less nutritional benefits, were sicker and died younger), but institutional reproduction was easier. This allowed farming communities to beat hunter-gatherer societies in inter-group competition.
These clans evolved culturally to foster cooperation and internal cohesion. They first developed around kin-based institutions which allowed for strong cooperation within clans. To scale up, they then turned to segmentary lineages which linked clans that shared common ancestors. Psychologically, this descent-based institution is based on personal and corporate honor. These segmentary lineages also dominate in inter-group competition, but they lack centralized and hierarchical authorities in order to scale up.
In a similar manner, the development of pre-modern states was also built on these kin-based institutions and chiefdoms emerging from the domination of one clan over others. This domination is mostly due to the manipulation and accumulation of ritual powers and offices of some clans over others. Such stratified kingdoms can blossom into premodern states and kingdoms, procuring new bureaucratic institutions between the elite ruling families and the clans or other kin-groups that dominate the rest of the population.
Evolution is like a rocky roller coaster in the dark. Over time, clans resisted subordination and turned into chiefdoms, and chiefdoms resisted conquest and assimilation by other chiefdoms, etc… Nonetheless, intergroup competition meant that any institutional element that fostered productivity, security, fertility or military success spread in the various ways described above.
Religion is one of the fundamental elements in the development of these institutions. It has had an influence on intergroup competition for instance: when gods are susceptible to punish you, some behaviors can be shaped in a society, making it easier to spread the behavior within and beyond one’s society. Under the pressure of intergroup competition, gods that (1) promote cooperation and harmony within groups, (2) are better at monitoring people and (3) have the power to punish people will be favored. They will foster scaling-up of societies, cooperation between people and communities and, hence, encourage economic growth.
Religions also have a strong impact on the psychology of people: several studies have shown that religious people are more cooperative and selfless when the idea of god is recalled, even unconsciously. Religion increases trust, legitimizes political authority and expands people’s conceptions of their communities, shifting from clans to all people sharing their religion.
The roots of WEIRD families can be found in doctrines, prohibitions and prescriptions that the catholic Church gradually adopted and promoted. The particularity of this Church is that it does not only compete with other religions but also with intensive kin-based institutions. By undermining the relationships between people and their clans, people were pushed to devote themselves to the Church.
Before the expansion of the Church, European tribes had institutions sharing kin-based ties. But, the marriage and family program undertaken by the Church (no marriage between cousins, no adoption, no remarriage, …) undermined these ties. It shook up the rule of inheritance and ownership allowing the Church to benefit from donations from ending dynasties (giving in return for the right to go to heaven). The dominance of the catholic Church (and its enrichment) was built on its capacity to destroy old institutions based on kinship, which in turn had strong and lasting effects on western psychology.
Kinship intensity is linked with tightness, conformism (Asch experiment), low levels of individualism, low out-of-group trust, shame rather than guilt and low universalism. People from countries with intensive kin-based institutions conform more to other’s responses, show low levels of cooperation in economic games and do not have the same behavior facing punishment (they turn more to revenge behavior).
Looking at the expansion of western churches over time, the broad patterns of psychological variation are consistent with a causal pathway going from the church’s marriage and family programs, to the reduction of kinship intensity and finally to the shifts of psychological pattern observed in WEIRD people.
To a lesser extent, similar psychological variations can be observed in other regions of the world for different reasons. For example, in some regions of China and India, ecological and climatic factors allow for the particularly productive cultivation of paddy rice, requiring the cooperation of large groups (to build and secure important irrigation infrastructure). The resulting agricultural intensification has led to the development of institutions strongly linked to kinship (patrilineal clans), which allow for greater cooperation between individuals. These individuals exhibit different psychological characteristics from adjacent areas where paddy rice cultivation is less favorable.
To understand the extent of the changes that the Catholic family program may have brought about, one can look at the example of monogamy. Globally, this is an uncommon practice (8% of the world population), which has a psychological and hormonal impact on men. By reducing competition between men, it leads to psychological changes that reduce violence and encourage confidence and investments in the future.
Psychological variations in individuals vary based on many phenomena. Studies have shown that increased trade leads to an increased trust in strangers, desire for equity, and cooperation. Similarly, war leads to greater inter-group cooperation and reinforces norms (both social and religious). These impacts may have different social effects depending on the psychological background of the individuals involved. In the case of Western Europe, the pervasiveness of war and the development of trade, coupled with the Church’s family agenda, led to the creation of new organizations such as guilds, cities, universities, and monasteries that developed strongly during the Middle Ages.
The economic development that followed can be linked to all of these psychological changes and their reciprocal links to the institutions that resulted from them. For example, innovations are rarely the source of isolated geniuses. They emerge in societies where knowledge flows are highly mobile. They are therefore linked to social factors: immigration, urbanization, development of universities, knowledge of foreign languages; as well as to cultural factors: cooperation and trust between individuals, refusal to conform, tolerance of differences, preference for novelty, etc. So global psychology patterns could have a strong influence on economic prosperity.
WEIRD psychology – individualism, an analytical spirit, impersonal pro-sociality – has also favored the development of laws, norms and general principles that apply to the whole population, as well as the emergence of democratic and representative governance. The Protestant religion is also a product of WEIRD psychology: it is a strongly individualistic religion, which places the subject and his relationship with God at the center of spiritual life. This religion has, reciprocally, strongly modified people’s psychology. Strong causal links exist between the expansion of the Protestant religion and the expansion of literacy.
Finally, the breakdown of kinship-based institutions caused by the Catholic Church brought about psychological changes and led to the emergence of new institutions, which in turn changed the way people thought. The emergence of new social rules (democracy, universal rules), as well as economic prosperity (through the development of trade and innovations) can be traced back to the reciprocal links between the psychology of people and the institutions established over time. The resulting political, economic and military power allowed European institutions to spread around the world, but also led to atrocities such as colonization and slavery.
By presenting a large number of studies from natural experiments and behavioral economics, Joseph Henrich shows how psychological variations have evolved over time through human beings’ cultural evolution and how important it is to take them into account in social sciences. For instance, a public policy will not have the same effect depending on the psychology of the people affected by it. Thus, psychological patterns should be taken into account more in public policy design, and in economic studies.
Edouard Pignède, PhD student Adaption to climate change: Inequalities and spatial vulnerability in rural areas of Sub-Saharan Africa.
 Henrich, J., 2020, The Weirdest People in the World, How the West became psychologically peculiar and particularly prosperous, Edition Farrar Straus & Giroux, p. 680.