Social and Behavioral Sciences Commons^™

Coordination And Evolutionary Dynamics: When Are Evolutionary Models Reliable?, Daniel Graydon Stephenson

ESI Publications

This study reports a continuous-time experimental test of evolutionary models in coordinated attacker–defender games. It implements three experimental treatment conditions: one with strong coordination incentives, one with weak coordination incentives, and one with zero coordination incentives. Each treatment exhibits identical equilibrium predictions but distinct evolutionary predictions. Observed behavior was tightly clustered around equilibrium under both the zero coordination treatment and the weak coordination treatment but widely dispersed from equilibrium under the strong coordination treatment. This result was anticipated by explicitly dynamic models but not by conventional stability criteria. In contrast to the widely maintained assumption of sign-preservation, subjects frequently switched …

Variation Among Populations In The Immune Protein Composition Of Mother's Milk Reflects Subsistence Pattern, Laura D. Klein, Jincui Huang, Elizabeth A. Quinn, Melanie A. Martin, Alicia A. Breakey, Michael Gurven, Hillard Kaplan, Claudia Valeggia, Grazyna Jasienska, Brooke Scelza, Carlito B. Lebrilla, Katie Hinde

ESI Publications

Lay Summary: Adaptive immune proteins in mothers’ milk are more variable than innate immune proteins across populations and subsistence strategies. These results suggest that the immune defenses in milk are shaped by a mother’s environment throughout her life.

Background and objectives: Mother’s milk contains immune proteins that play critical roles in protecting the infant from infection and priming the infant’s developing immune system during early life. The composition of these molecules in milk, particularly the acquired immune proteins, is thought to reflect a mother’s immunological exposures throughout her life. In this study, we examine the composition of innate …

Do Negative Random Shocks Affect Trust And Trustworthiness?, Hernán Bejerano, Joris Gillet, Ismael Rodriguez-Lara

ESI Publications

We report data from a variation of the trust game aimed at determining whether (and how) inequality and random shocks that affect wealth influence the levels of trust and trustworthiness. To tease apart the effect of the shock and the inequality, we compare behavior in a trust game where the inequality is initially given and one where it is the result of a random shock that reduces the second mover's endowment. We find that first‐movers send less to second‐movers but only when the inequality results from a random shock. As for the amount returned, second‐movers return less when they are …

Do Negative Random Shocks Affect Trust And Trustworthiness?, Hernán Bejerano, Joris Gillet, Ismael Rodriguez-Lara

ESI Publications

We report data from a variation of the trust game aimed at determining whether (and how) inequality and random shocks that affect wealth influence the levels of trust and trustworthiness. To tease apart the effect of the shock and the inequality, we compare behavior in a trust game where the inequality is initially given and one where it is the result of a random shock that reduces the second mover's endowment. We find that first‐movers send less to second‐movers but only when the inequality results from a random shock. As for the amount returned, second‐movers return less when they are …

Marital Violence And Fertility In A Relatively Egalitarian High-Fertility Population, Jonathan Stieglitz, Benjamin C. Trumble, Hillard Kaplan, Michael Gurven

ESI Publications

Ultimate and proximate explanations of men’s physical intimate partner violence (IPV) against women have been proposed. An ultimate explanation posits that IPV is used to achieve a selfish fitness-relevant outcome, and predicts that IPV is associated with greater marital fertility. Proximate IPV explanations contain either complementary strategic components (for example, men’s desire for partner control), non-strategic components (for example, men’s self-regulatory failure), or both strategic and non-strategic components involving social learning. Consistent with an expectation from an ultimate IPV explanation, we find that IPV predicts greater marital fertility among Tsimané forager-horticulturalists of Bolivia (n = 133 marriages, 105 women). This …

Correction To: 'Greater Wealth Inequality, Less Polygyny: Rethinking The Polygyny Threshold Model', Cody T. Ross, Monique Borgerhoff Mulder, Seung-Yun Oh, Samuel Bowles, Bret Beheim, John Bunce, Mark Caudell, Gregory Clark, Heidi Colleran, Carmen Cortez, Patricia Draper, Russell D. Greaves, Michael Gurven, Thomas Headland, Janet Headland, Kim Hill, Barry Hewlett, Hillard Kaplan, Jeremy Koster, Karen Kramer, Frank Marlowe, Richard Mcelereath, David Nolin, Marsha Quinlan, Robert Quinlan, Caissa Revilla-Minaya, Brooke Scelza, Ryan Schacht, Mary Shenk, Ray Uehara, Eckart Voland, Kai Willführ, Bruce Winterhalder, John Ziker, Christopher Von Rueden

ESI Publications

No abstract provided.

Greater Wealth Inequality, Less Polygyny: Rethinking The Polygyny Threshold Model, Cody T. Ross, Monique Borgerhoff Mulder, Seung-Yun Oh, Samuel Bowles, Bret Beheim, John Bunce, Mark Caudell, Gregory Clark, Heidi Colleran, Carmen Cortez, Patricia Draper, Russell D. Greaves, Michael Gurven, Thomas Headland, Janet Headland, Kim Hill, Barry Hewlett, Hillard Kaplan, Jeremy Koster, Karen Kramer, Frank Marlowe, Richard Mcelreath, David Nolin, Marsha Quinlan, Robert Quinlan, Caissa Revilla-Minaya, Brooke Scelza, Ryan Schacht, Mary Shenk, Ray Uehara, Eckart Voland, Kai Willführ, Bruce Winterhalder, John Ziker, Christopher Von Rueden

ESI Publications

Monogamy appears to have become the predominant human mating system with the emergence of highly unequal agricultural populations that replaced relatively egalitarian horticultural populations, challenging the conventional idea—based on the polygyny threshold model—that polygyny should be positively associated with wealth inequality. To address this polygyny paradox, we generalize the standard polygyny threshold model to a mutual mate choice model predicting the fraction of women married polygynously. We then demonstrate two conditions that are jointly sufficient to make monogamy the predominant marriage form, even in highly unequal societies. We assess if these conditions are satisfied using individual-level data from 29 human …

Sleep Variability And Nighttime Activity Among Tsimane Forager‐Horticulturalists, Gandhi Yetish, Hillard Kaplan, Michael Gurven

ESI Publications

Objectives

A common presumption in sleep research is that “normal” human sleep should show high night‐to‐night consistency. Yet, intra‐individual sleep variation in small‐scale subsistence societies has never been studied to test this idea. In this study, we assessed the degree of nightly variation in sleep patterns among Tsimane forager‐horticulturalists in Bolivia, and explored possible drivers of the intra‐individual variability.

Methods

We actigraphically recorded sleep among 120 Tsimane adults (67 female), aged 18–91, for an average of 4.9 nights per person using the Actigraph GT3X and Philips Respironics Actiwatch 2. We assessed intra‐individual variation using intra‐class correlations and average deviation from …

Land Assembly With Taxes, Not Takings, Mark Desantis, Matthew W. Mccarter, Abel Winn

ESI Publications

We use a novel tax mechanism – ‘rejected offer reassessment’ (ROR) – in laboratory experiments to discourage seller holdout and facilitate land assembly. Under this mechanism, if a landowner rejects a developer’s offer, his taxable property value is reassessed to be equal to the rejected offer, increasing his taxes. We find that, relative to a control treatment, ROR discourages the magnitude of seller holdout (but not its frequency) and increases the rate of successful land assembly by almost 60%. It also increases the gains from trade by 22.1% relative to the control treatment, but the difference is not statistically significant.

Goal Setting In The Principal-Agent Model: Weak Incentives For Strong Performance, Brice Corgnet, Joaquín Gómez-Miñambres, Roberto Hernán-González

ESI Publications

We study a principal–agent framework in which principals can assign wage-irrelevant goals to agents. We find evidence that, when given the possibility to set wage-irrelevant goals, principals select incentive contracts for which pay is less responsive to agents' performance. Agents' performance is higher in the presence of goal setting despite weaker incentives. We develop a principal–agent model with reference-dependent utility that illustrates how labor contracts combining weak monetary incentives and wage-irrelevant goals can be optimal. The pervasive use of non-monetary incentives in the workplace may help account for previous empirical findings suggesting that firms rely on unexpectedly weak monetary incentives.

A Theory Of Focal Points In 2x2 Games, Jonathan W. Leland, Mark Schneider

ESI Publications

Since the classic work of Schelling, the notion of a focal point has been widely applied to explain coordinated behavior. However, focal points remain largely outside the formal apparatus of game theory. This paper develops a model of play in 2 × 2 games where payoff differences determine what strategy players will perceive as “salient” and choose to play. The model uniquely predicts which outcome will emerge for virtually the entire class of 2 × 2 normal form games. For the subset of such games involving coordination and asymmetric payoffs, payoff differences identify focal outcomes and strategies in the same …

Sex Differences In Political Leadership In An Egalitarian Society, Christopher Von Rueden, Sarah Alami, Hillard Kaplan, Michael Gurven

ESI Publications

We test the contribution of sex differences in physical formidability, education, and cooperation to the acquisition of political leadership in a small-scale society. Among forager-farmers from the Bolivian Amazon, we find that men are more likely to exercise different forms of political leadership, including verbal influence during community meetings, coordination of community projects, and dispute resolution. We show that these differences in leadership are not due to gender per se but are associated with men’s greater number of cooperation partners, greater access to schooling, and greater body size and physical strength. Men’s advantage in cooperation partner number is tied to …

Low Perceived Control Over Health Is Associated With Lower Treatment Uptake In A High Mortality Population Of Bolivian Forager-Farmers, Sarah Alami, Jonathan Stieglitz, Hillard Kaplan, Michael Gurven

ESI Publications

Indigenous people worldwide suffer from higher rates of morbidity and mortality than neighboring populations. In addition to having limited access to public health infrastructure, indigenous people may also have priorities and health perceptions that deter them from seeking adequate modern healthcare. Here we propose that living in a harsh and unpredictable environment reduces motivation to pursue deliberate, costly action to improve health outcomes. We assess whether variation in Health Locus of Control (HLC), a psychological construct designed to capture self-efficacy with respect to health, explains variation in treatment uptake behavior among Tsimane Amerindians (N=690; age range: 40–89 years; 55.8% female; …