Maciej Chudek

Culture–gene coevolution, norm-psychology and the emergence of human prosociality

Diverse lines of theoretical and empirical research are converging on the notion that human evolution has been substantially influenced by the interaction of our cultural and genetic inheritance systems. The application of this culture-gene coevolutionary approach to understanding human social psychology has generated novel insights into the cognitive and affective foundations of large-scale cooperation, social norms and ethnicity. This approach hypothesizes a norm-psychology: a suite of psychological adaptations for inferring, encoding in memory, adhering to, enforcing and redressing violations of the shared behavioral standards of ones community. After reviewing the substantial body of formal theory underpinning these predictions, we outline how this account organizes diverse empirical findings in the cognitive sciences and related disciplines. Norm-psychology offers explanatory traction on the evolved psychological mechanisms that underlie cultural evolution, cross-cultural differences and the emergence of norms.

Evidence for a Sensitive Period for Acculturation Younger Immigrants Report Acculturating at a Faster Rate

Though recent adult immigrants often seem less acculturated to their new society than people who immigrated as children, it is not clear whether this difference is driven by duration of exposure or exposure during a sensitive developmental period. In a study aimed at disambiguating these influences, community and student samples of Hong Kong immigrants to Vancouver, Canada, completed the Vancouver Index of Acculturation, a measure that assesses respondents’ identification with their mainstream and heritage cultures. A longer duration of exposure was found to be associated with greater identification with Canadian culture only at younger ages of immigration, but not at later ages of immigration. Conversely, identification with Chinese culture was unaffected by either age of immigration or length of exposure to Canadian culture. These findings provide evidence for a sensitive period for acculturation: People are better able to identify with a host culture the longer their exposure to it, but only if this exposure occurs when they are relatively young.

The Big Man Mechanism: how prestige fosters cooperation and creates prosocial leaders

Anthropological evidence from diverse societies suggests that prestige-based leadership may provide a foundation for cooperation in many contexts. Here, inspired by such ethnographic observations and building on a foundation of existing research on the evolution of prestige, we develop a set of formal models to explore when an evolved prestige psychology might drive the cultural evolution of n-person cooperation, and how such a cultural evolutionary process might create novel selection pressures for genes that make prestigious individuals more prosocial. Our results reveal (i) how prestige can foster the cultural emergence of cooperation by generating correlated behavioural phenotypes, both between leaders and followers, and among followers; (ii) why, in the wake of cultural evolution, natural selection favours genes that make prestigious leaders more prosocial, but only when groups are relatively small; and (iii), why the effectiveness of status differences in generating cooperation in large groups depends on cultural transmission (and not primarily on deference or coercion). Our theoretical framework, and the specific predictions made by these models, sketch out an interdisciplinary research programme that cross-cuts anthropology, biology, psychology and economics. Some of our predictions find support from laboratory work in behavioural economics and are consistent with several real-world patterns.

US Immigrants’ Patterns of Acculturation are Sensitive to Their Age, Language, and Cultural Contact but Show No Evidence of a Sensitive Window for Acculturation

Recent research observed a sensitive window, at about 14 years of age, in the acculturation rates of Chinese immigrants to Canada. Tapping an online sample of us immigrants (n=569), we tested these relationships in a broader population and explored connections with new potentially causally related variables: formal education, language ability and contact with heritage-culture and mainstream United States individuals, both now and at immigration. While we found that acculturation decreased with age at immigration and increased with years in the us, we did not observe a similar sensitive window (i.e., change in rate with age). We also present an exploratory path analysis, exposing the relationships in our sample between acculturation and the variables above. The novel relationships documented here can improve theorising about this rich and complex empirical phenomenon.

The Challenges of Qualitatively Coding Ancient Texts.

We respond to several important and valid concerns about our study (‘‘The Prevalence of Folk Dualism in Early China,’’ Cognitive Science 35: 997–1007) by Klein and Klein, defending our interpretation of our data. We also argue that, despite the undeniable challenges involved in qualitatively coding texts from ancient cultures, the standard tools used throughout the cognitive sciences—large quantities of data, coders as blind to the hypothesis as possible, intercoder reliability measures, and statistical analysis—allow the noise of randomly distributed interpretative differences to be distinguished from the signal of genuine historical patterns.

Understanding the research program

The target article misunderstands the research program it criticizes. The work of Boyd, Richerson, Fehr, Gintis, Bowles and their collaborators has long included the theoretical and empirical study of models both with and without diffuse costly punishment. In triaging the situation, we aim to (1) clarify the theoretical landscape, (2) highlight key points of agreement, and (3) suggest a more productive line of debate.

The cultural brain hypothesis: how culture drives brain expansion, underlies sociality, and alters life history

In the last few million years, the hominin brain more than tripled in size. Comparisons across evolutionary lineages suggest that this expansion may be part of a broader trend toward larger, more complex brains in many taxa. Efforts to understand the evolutionary forces driving brain expansion have focused on climatic, ecological, and social factors. Here, building on existing research on learning, we analytically and computationally model the predictions of two closely related hypotheses: The Cultural Brain Hypothesis and the Cumulative Cultural Brain Hypothesis. The Cultural Brain Hypothesis posits that brains have been selected for their ability to store and manage information, acquired through asocial or social learning. The model of the Cultural Brain Hypothesis reveals relationships between brain size, group size, innovation, social learning, mating structures, and the length of the juvenile period that are supported by the existing empirical literature. From this model, we derive a set of predictions—the Cumulative Cultural Brain Hypothesis—for the conditions that favor an autocatalytic take-off characteristic of human evolution. This narrow evolutionary pathway, created by cumulative cultural evolution, may help explain the rapid expansion of human brains and other aspects of our species’ life history and psychology.

Do minds switch bodies? Dualist interpretations across ages and societies

ABSTRACT Researchers explain cultural phenomena ranging from cognitive biases to widespread religious beliefs by assuming intuitive dualism: humans imagine minds and bodies as distinct and separable. We examine dualist intuition development across two societies that differ in normative focus on thinking about minds. We use a new method that measures people’s tendency to interpret ambiguous stimuli using mind-body dualist thinking. We recruited 180 Canadian children (2–10 yrs) along with 42 Indigenous iTaukei Fijian children (5–13 yrs) and 38 Indigenous iTaukei Fijian adults (27–79 yrs) from a remote island community. Participants tracked a named character within ambiguous animations that could be interpreted as a mind-body switch. Animations vary “agency cues” that participants might rely on for dualistic interpretations. Results indicate early emerging dualistic inclinations across populations and reliance on “agency cues” of body proximity and appearance of eyes. “Agency cues” increase dualist interpretations from 10% to 70%, though eyes mattered more for Westernized participants. Overall, statistical models positing that dualist interpretations “emerge early and everywhere” fit our data better than models positing that dualism “develops gradually with exposure to Western cultural traditions.” Fijian participants, who normatively avoid focus on minds, offered even more dualistic interpretations when they had less Western cultural exposure (via formal education).