Chudek, M., and J. Henrich. “Tackling Group-Level Traits by Starting at the Start.” Behavioral and Brain Sciences 37, no. 3 (2014): 256-7. PDF
Bauer, M., A. Cassar, J. Chytilova, and J. Henrich. “War's Enduring Effects on the Development of Egalitarian Motivations and In-Group Biases.” Psychological Science 25, no. 1 (2014): 47-57.Abstract

In suggesting that new nations often coalesce in the decades following war, historians have posed an important psychological question: Does the experience of war generate an enduring elevation in people's egalitarian motivations toward their in-group? We administered social-choice tasks to more than 1,000 children and adults differentially affected by wars in the Republic of Georgia and Sierra Leone. We found that greater exposure to war created a lasting increase in people's egalitarian motivations toward their in-group, but not their out-groups, during a developmental window starting in middle childhood (around 7 years of age) and ending in early adulthood (around 20 years of age). Outside this window, war had no measurable impact on social motivations in young children and had only muted effects on the motivations of older adults. These war effects are broadly consistent with predictions from evolutionary approaches that emphasize the importance of group cooperation in defending against external threats, though they also highlight key areas in need of greater theoretical development.



Cheng, J. T., J. L. Tracy, T. Foulsham, A. Kingstone, and J. Henrich. “Two Ways to the Top: Evidence That Dominance and Prestige Are Distinct Yet Viable Avenues to Social Rank and Influence.” Journal of Personality and Social Psychology 104, no. 1 (2013): 103-125. PDF
Silk, J. B., S. F. Brosnan, J. Henrich, S. P. Lambeth, and S. Shapiro. “Chimpanzees share food for many reasons: the role of kinship, reciprocity, social bonds and harassment on food transfers.” Animal Behaviour 85, no. 5 (2013): 941-947. PDF
Tracy, J. L., A. F. Shariff, W. Zhao, and J. Henrich. “Cross-cultural evidence that the pride expression is a universal automatic status signal.” Journal of Experimental Psychology-General 142, no. 1 (2013): 163-180. PDF Supplement
Boyd, R., P. J. Richerson, J. Henrich, and J. Lupp. “The Cultural Evolution of Technology:Facts and theories.” In Cultural Evolution: Society, Language, and Religion, edited by P. J. Richerson and M. H. Christiansen. Vol. 12. Cambridge, MA: MIT Press, 2013.
Chudek, M., Wanying Zhao, and Joseph Henrich. “Culture-Gene Coevolution, Large-Scale Cooperation and the Shaping of Human Social Psychology.” In Signaling, Commitment, and Emotion, edited by Richard Joyce, Kim Sterelny, and Brett Calcott, 425-458. Cambridge: MIT Press, 2013.
Chudek, M., Patricia E Brosseau‐Liard, Susan Birch, and J. Henrich. “Culture-gene coevolutionary theory and children’s selective social learning.” In Navigating the social world: What infants, children, and other species can teach us, edited by Mahzarin R. Banaji and Susan A Gelman, 181. Oxford: Oxford University Press, 2013.
House, B., J. Henrich, B. Sarnecka, and J. B. Silk. “The development of contingent reciprocity in children.” Evolution and Human Behavior 34, no. 2 (2013): 86-93.Abstract

Cooperation between nonrelatives is common in humans. Reciprocal altruism is a plausible evolutionary mechanism for cooperation within unrelated pairs, as selection may favor individuals who selectively cooperate with those who have cooperated with them in the past. Reciprocity is often observed in humans, but there is only limited evidence of reciprocal altruism in other primate species, raising questions about the origins of human reciprocity. Here, we explore how reciprocity develops in a sample of American children ranging from 3 to 7.5 years of age, and also compare children's behavior to that of chimpanzees in prior studies to gain insight into the phylogeny of human reciprocity. Children show a marked tendency to respond contingently to both prosocial and selfish acts, patterns that have not been seen among chimpanzees in prior studies. Our results show that reciprocity increases markedly with age in this population of children, and by about 5.5 years of age children consistently match the previous behavior of their partners. (C) 2013 Published by Elsevier Inc.

Barrett, H. C., T. Broesch, R. M. Scott, Z. J. He, R. Baillargeon, D. Wu, M. Bolz, et al.Early false-belief understanding in traditional non-Western societies.” Proceedings of the Royal Society B-Biological Sciences 280, no. 1755 (2013): 20122654.Abstract

The psychological capacity to recognize that others may hold and act on false beliefs has been proposed to reflect an evolved, species-typical adaptation for social reasoning in humans; however, controversy surrounds the developmental timing and universality of this trait. Cross-cultural studies using elicited-response tasks indicate that the age at which children begin to understand false beliefs ranges from 4 to 7 years across societies, whereas studies using spontaneous-response tasks with Western children indicate that false-belief understanding emerges much earlier, consistent with the hypothesis that false-belief understanding is a psychological adaptation that is universally present in early childhood. To evaluate this hypothesis, we used three spontaneous-response tasks that have revealed early false-belief understanding in the West to test young children in three traditional, non-Western societies: Salar (China), Shuar/Colono (Ecuador) and Yasawan (Fiji). Results were comparable with those from the West, supporting the hypothesis that false-belief understanding reflects an adaptation that is universally present early in development.

Hruschka, Daniel Jacob, and Joseph Henrich. “Economic and evolutionary hypotheses for cross-population variation in parochialism.” Frontiers in Human Neuroscience 7, no. 559 (2013): doi: 10.3389/fnhum.2013.00559.Abstract

Human populations differ reliably in the degree to which people favor family, friends, and community members over strangers and outsiders. In the last decade, researchers have begun to propose several economic and evolutionary hypotheses for these cross-population differences in parochialism. In this paper, we outline major current theories and review recent attempts to test them. We also discuss the key methodological challenges in assessing these diverse economic and evolutionary theories for cross-population differences in parochialism.

Slingerland, Edward, Joseph Henrich, and Ara Norenzayan. “The evolution of prosocial religions.” In Cultural Evolution: Society, Technology, Language and Religion, edited by Peter J Richerson and M. H. Christiansen. Cambridge: MIT Press, 2013.
Hruschka, Daniel J, and Joseph Henrich. “Institutions, parasites and the persistence of in-group preferences.” PloS One 8, no. 5 (2013): e63642. PDF
Henrich, J., and J. B. Silk. “Interpretative Problems with Chimpanzee Ultimatum Games[Comment on Proctor et. al.].” PNAS, 2013, 110, 33, E3049. For an extended critique see SSRN PDF
House, B. R., J. B. Silk, J. Henrich, H. C. Barrett, B. A. Scelza, A. H. Boyette, B. S. Hewlett, R. McElreath, and S. Laurence. “Ontogeny of prosocial behavior across diverse societies.” Proceedings of the National Academy of Sciences of the United States of America 110, no. 36 (2013): 14586-14591.Abstract

Humans are an exceptionally cooperative species, but there is substantial variation in the extent of cooperation across societies. Understanding the sources of this variability may provide insights about the forces that sustain cooperation. We examined the ontogeny of prosocial behavior by studying 326 children 3-14 y of age and 120 adults from six societies (age distributions varied across societies). These six societies span a wide range of extant human variation in culture, geography, and subsistence strategies, including foragers, herders, horticulturalists, and urban dwellers across the Americas, Oceania, and Africa. When delivering benefits to others was personally costly, rates of prosocial behavior dropped across all six societies as children approached middle childhood and then rates of prosociality diverged as children tracked toward the behavior of adults in their own societies. When prosocial acts did not require personal sacrifice, prosocial responses increased steadily as children matured with little variation in behavior across societies. Our results are consistent with theories emphasizing the importance of acquired cultural norms in shaping costly forms of cooperation and creating cross-cultural diversity.

Norenzayan, A., J. Henrich, and E. Slingerland. “Religious prosociality: a synthesis.” In Cultural Evolution: Society, Technology, Language and Religion, edited by P. J. Richerson and M. H. Christiansen, 365-380. Cambridge: MIT Press, 2013.
Muthukrishna, Michael, Ben W Shulman, Vlad Vasilescu, and Joseph Henrich. “Sociality influences cultural complexity.” Proceedings of the Royal Society B: Biological Sciences 281, no. 1774 (2013): 20132511. PDF
Kline, M. A., R. Boyd, and J. Henrich. “Teaching and the Life History of Cultural Transmission in Fijian Villages.” Human Nature-an Interdisciplinary Biosocial Perspective 24, no. 4 (2013): 351-374.Abstract

Much existing literature in anthropology suggests that teaching is rare in non-Western societies, and that cultural transmission is mostly vertical (parent-to-offspring). However, applications of evolutionary theory to humans predict both teaching and non-vertical transmission of culturally learned skills, behaviors, and knowledge should be common cross-culturally. Here, we review this body of theory to derive predictions about when teaching and non-vertical transmission should be adaptive, and thus more likely to be observed empirically. Using three interviews conducted with rural Fijian populations, we find that parents are more likely to teach than are other kin types, high-skill and highly valued domains are more likely to be taught, and oblique transmission is associated with high-skill domains, which are learned later in life. Finally, we conclude that the apparent conflict between theory and empirical evidence is due to a mismatch of theoretical hypotheses and empirical claims across disciplines, and we reconcile theory with the existing literature in light of our results.

Nakahashi, Wataru, Joe Yuichiro Wakano, and Joseph Henrich. “Adaptive social learning strategies in temporally and spatially varying environments.” Human Nature 23, no. 4 (2012): 386-418. PDF
Henrich, J., R. Boyd, R. McElreath, M. Gurven, P. J. Richerson, J. Ensminger, M. Alvard, et al.Culture does account for variation in game behavior.” Proceedings of the National Academy of Sciences of the United States of America 109, no. 2 (2012): E32-E33. PDF Extended Version