Michael Muthukrishna

Sociality influences cultural complexity

Archaeological and ethnohistorical evidence suggests a link between a populations size and structure, and the diversity or sophistication of its toolkits or technologies. Addressing these patterns, several evolutionary models predict that both the size and social interconnectedness of populations can contribute to the complexity of its cultural repertoire. Some models also predict that a sudden loss of sociality or of population will result in subsequent losses of useful skills/technologies. Here, we test these predictions with two experiments that permit learners to access either one or five models (teachers). Experiment 1 demonstrates that naive participants who could observe five models, integrate this information and generate increasingly effective skills (using an image editing tool) over 10 laboratory generations, whereas those with access to only one model show no improvement. Experiment 2, which began with a generation of trained experts, shows how learners with access to only one model lose skills (in knot-tying) more rapidly than those with access to five models. In the final generation of both experiments, all participants with access to five models demonstrate superior skills to those with access to only one model. These results support theoretical predictions linking sociality to cumulative cultural evolution.

Understanding cumulative cultural evolution

In a narrow critique of two early papers in the literature on cumulative cultural evolution, Vaesen et al. (1) misunderstand the work they criticize, mischaracterize multiple lines of research, and selectively ignore much evidence. While largely recycling prior criticisms, they provide no new models, evidence, or explanations (2). Not only do their criticisms of Henrich’s (3) and Powell et al.’s (4) modeling assumptions miss their mark (2), but Vaesen et al. (1) also ignore many other models that do not rely on these assumptions yet arrive at similar predictions. These other models variously include conformist transmission and explore these processes using nonnormal distributions, discrete traits, networks, etc. (2, 5). Of course, no … [↵][1]1To whom correspondence should be addressed. Email: henrich{at}fas.harvard.edu. [1]: #xref-corresp-1-1

The social and cultural roots of whale and dolphin brains

Encephalization, or brain expansion, underpins humans’ sophisticated social cognition, including language, joint attention, shared goals, teaching, consensus decision-making and empathy. These abilities promote and stabilize cooperative social interactions, and have allowed us to create a ‘cognitive’ or ‘cultural’ niche and colonize almost every terrestrial ecosystem. Cetaceans (whales and dolphins) also have exceptionally large and anatomically sophisticated brains. Here, by evaluating a comprehensive database of brain size, social structures and cultural behaviours across cetacean species, we ask whether cetacean brains are similarly associated with a marine cultural niche. We show that cetacean encephalization is predicted by both social structure and by a quadratic relationship with group size. Moreover, brain size predicts the breadth of social and cultural behaviours, as well as ecological factors (diversity of prey types and to a lesser extent latitudinal range). The apparent coevolution of brains, social structure and behavioural richness of marine mammals provides a unique and striking parallel to the large brains and hyper-sociality of humans and other primates. Our results suggest that cetacean social cognition might similarly have arisen to provide the capacity to learn and use a diverse set of behavioural strategies in response to the challenges of social living.Cetaceans show a similar increase in brain size as is seen in human evolution. Here, this increase is shown to be linked to an expansion in the social and ecological niche.

What is the association between religious affiliation and children’s altruism?

Decety et al.[1] examined the relationships between household religiosity and sociality in children sampled from six countries. We were keenly interested in Decety et al.[1]s conclusions about a negative relationship between religiosity and generosity - measured with the Dictator Game - as our team has investigated related questions, often with potentially contrasting findings [2-5]. We argue here that, after addressing peculiarities in their analyses, Decety et al.[1]s data are consistent with a different interpretation.

Corrupting cooperation and how anti-corruption strategies may backfire

Understanding how humans sustain cooperation in large, anonymous societies remains a central question of both theoretical and practical importance. In the laboratory, experimental behavioural research using tools like public goods games suggests that cooperation can be sustained by institutional punishment—analogous to governments, police forces and other institutions that sanction free-riders on behalf of individuals in large societies1,2,3. In the real world, however, corruption can undermine the effectiveness of these institutions4,5,6,7,8. Levels of corruption correlate with institutional, economic and cultural factors, but the causal directions of these relationships are difficult to determine5,6,8–10. Here, we experimentally model corruption by introducing the possibility of bribery. We investigate the effect of structural factors (a leader’s punitive power and economic potential), anti-corruption strategies (transparency and leader investment in the public good) and cultural background. The results reveal that (1) corruption possibilities cause a large (25%) decrease in public good provisioning, (2) empowering leaders decreases cooperative contributions (in direct opposition to typical institutional punishment results), (3) growing up in a more corrupt society predicts more acceptance of bribes and (4) anti-corruption strategies are effective under some conditions, but can further decrease public good provisioning when leaders are weak and the economic potential is poor. These results suggest that a more nuanced approach to corruption is needed and that proposed panaceas, such as transparency, may actually be harmful in some contexts.

Theories of the deep: combining salience and network analyses to produce mental model visualizations of a coastal British Columbia food web

Arriving at shared mental models among multiple stakeholder groups can be crucial for successful management of contested social-ecological systems (SES). Academia can help by first eliciting stakeholders’ initial, often tacit, beliefs about a SES, and representing them in useful ways. We demonstrate a new recombination of techniques for this purpose, focusing specifically on tacit beliefs about food webs. Our approach combines freelisting and sorting techniques, salience analysis, and ultimately network analysis, to produce accessible visualizations of aggregate mental models that can then be used to facilitate discussion or generate further hypotheses about cognitive drivers of conflict. The case study we draw upon to demonstrate this technique is Clayoquot Sound UNESCO Biosphere Reserve, on the west coast of British Columbia, Canada. There, an immanent upsurge in the sea otter (Enhydra lutris) population, which competes with humans for shellfish, has produced tension among government managers, and both First Nations and non-First Nations residents. Our approach helps explain this tension by visually highlighting which trophic relationships appear most cognitively salient among the lay public. We also include speculative representations of models held by managers, and pairs of contrasting demographic subgroups, to further demonstrate potential uses of the method.

Overconfidence is universal? Elicitation of Genuine Overconfidence (EGO) procedure reveals systematic differences across domain, task knowledge, and incentives in four populations

Overconfidence is sometimes assumed to be a human universal, but there remains a dearth of data systematically measuring overconfidence across populations and contexts. Moreover, cross-cultural experiments often fail to distinguish between placement and precision and worse still, often compare population-mean placement estimates rather than individual performance subtracted from placement. Here we introduce a procedure for concurrently capturing both placement and precision at an individual level based on individual performance: The Elicitation of Genuine Overconfidence (EGO) procedure. We conducted experiments using the EGO procedure, manipulating domain, task knowledge, and incentives across four populations—Japanese, Hong Kong Chinese, Euro Canadians, and East Asian Canadians. We find that previous measures of population-level overconfidence may have been misleading; rather than universal, overconfidence is highly context dependent. Our results reveal cross-cultural differences in sensitivity to incentives and differences in overconfidence strategies, with underconfidence, accuracy, and overconfidence. Comparing sexes, we find inconsistent results for overplacement, but that males are consistently more confident in their placement. These findings have implications for our understanding of the adaptive value of overconfidence and its role in explaining population-level and individual-level differences in economic and psychological behavior.

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.

Individual-level psychology and group-level traits

Psychological research on social influence illuminates many mechanisms through which role differentiation and collaborative interdependence may affect cultural evolution. We focus here on psychological processes that produce specific patterns of asymmetric influence, which in turn can have predictable consequences for the emergence and transmission of group-level traits.