Anonymity versus Privacy in the Dictator Game: Revealing Donor Decisions to Recipients Does Not Substantially Impact Donor Behavior

Anonymity is often offered in economic experiments in order to eliminate observer effects and induce behavior that would be exhibited under private circumstances. However, anonymity differs from privacy in that interactants are only unaware of each others' identities, while having full knowledge of each others' actions. Such situations are rare outside the laboratory and anonymity might not meet the requirements of some participants to psychologically engage as if their actions were private. In order to explore the impact of a lack of privacy on prosocial behaviors, I expand on a study reported in Dana et al. (2006) in which recipients were left unaware of the Dictator Game and given donations as “bonuses” to their show-up fees for other tasks. In the current study, I explore whether differences between a private Dictator Game (sensu Dana et al. (2006)) and a standard anonymous one are due to a desire by dictators to avoid shame or to pursue prestige. Participants of a Dictator Game were randomly assigned to one of four categories—one in which the recipient knew of (1) any donation by an anonymous donor (including zero donations), (2) nothing at all, (3) only zero donations, and (4) and only non-zero donations. The results suggest that a lack of privacy increases the shame that selfish-acting participants experience, but that removing such a cost has only minimal effects on actual behavior.The open access fee for this work was funded through the Texas A&M University Open Access to Knowledge (OAK) Fund

Father Death and Adult Success Among the Tsimane: Implications for Marriage and Divorce

Human fathers are heavily involved in the rearing of children around the world. While there is great cross-cultural variation, the father is a recognizable role in all populations. This deviates from the standard mammalian pattern of little paternal investment. A logical explanation offered early by evolutionary theorists is that human fathers evolved the capacity for paternal concern because human children are remarkably needy and impose a great encumbrance on the mother (Lancaster & Lancaster, 1983; Lovejoy, 1981). Thus, fathers have greater opportunity to enhance the wellbeing of child and mother, as there is a deeper well of need to fill. Marginal gains of family investment are thus steeper, leading to greater possibility for such returns to supersede those provided by the short-term mating strategies that are typical of most mammals. However, the numerous studies that have explored the cross-cultural impact of father presence on child survivorship report mixed results (Sear & Mace, 2008), indicating that father presence (and by assumption, investment) does not universally associate with better-off children. Fathers may also play an important role in enhancing the future competitiveness of their children by enhancing their physical condition, teaching them important skills, accumulating heritable wealth, or by building social alliances (Hewlett, 1992; Scelza, 2010). Previous studies have largely focused on the wellbeing of juvenile children, but a more complete test of the impact of paternal investment concerns its effect on the reproductive value of children, which must include adult fertility. Our goal in this paper is to fill this gap in the literature by reporting several measures of achieved success of adults based on the number of years their fathers were alive and present during their childhood. Specifically, we explore the impact of father presence on offspring height, body mass index (BMI), age of first reproduction, completed fertility for age, and number of surviving children for age. We report only one significant finding out of ten specific tests (five predictions for both men and women), thus failing to find any robust pattern of father death impacting the achieved success of adult children. Finally, we relate our findings to the nature of Tsimane marriage. Marriage in humans is often considered a means of facilitating the providing of bi-parental care (Hurtado & Hill, 1992; Lovejoy, 1981). Among the Tsimane, marriages are fairly stable, particularly after children have been born, strengthening the prediction that the presence of Tsimane fathers should be important to the success of children. We thus explore alternative explanations for the stability of Tsimane marriages by examining alternative fitness pathways and constraints experienced by Tsimane men

Infidelity, Jealousy, and Wife Abuse Among Tsimane Forager-Farmers: Testing Evolutionary Hypotheses of Marital Conflict

What causes marital conflict, and which marital conflicts are more likely to result in men’s violence against their wives? It has long been argued that men’s jealousy over women’s infidelity is the strongest impetus to men’s lethal and non-lethal violence against female partners. Less is known about the extent to which women’s jealousy over men’s infidelity precipitates men’s violence against female partners. Husbands are more likely than wives to commit infidelity, and men and women report a similar frequency and intensity of jealous emotions during recalls of potential infidelity. If men are likely to use time and resources for pursuit of extramarital sexual relationships, wives’ jealousy may play a critical role in mate retention, but at potential cost of instigating marital arguments and violence against wives. Given men’s greater size and strength, violence against wives may be used as a “bargaining” tool to strategically leverage a selfish outcome, despite potential costs to the victim, aggressor, and offspring. This is the first study to document content and prevalence of marital arguments, and prevalence of men’s violence against wives during such arguments in a small-scale society, the Tsimane of Bolivia. We show that men’s diversion of resources from the family is a major source of arguments between spouses and husbands’ violence against their wives. We argue that husbands employ violence to limit wives’ mate retention effort and maintain men’s opportunities to pursue extramarital sexual relationships. We define violence against wives as any physical contact initiated by a husband with intent to harm a wife (hereafter termed wife abuse). The research design minimizes response and sampling bias in two ways: 1) data are obtained independently from both spouses instead of only one spouse, permitting assessment of spousal consistency in reporting; and 2) couples are sampled randomly rather than being self-selected for a high degree of marital conflict

The Social Strategy Game: Resource Competition Within Female Social Networks Among Small-Scale Forager-Horticulturalists

This paper examines social determinants of resource competition among Tsimane Amerindian women of Bolivia. We introduce a semi-anonymous experiment (the Social Strategy Game) designed to simulate resource competition among women. Information concerning dyadic social relationships and demographic data were collected to identify variables influencing resource competition intensity, as measured by the number of beads one woman took from another. Relationship variables are used to test how the affiliative or competitive aspects of dyads affect the extent of prosociality in the game. Using a mixed-modeling procedure, we find that women compete with those with whom they are quarreling over accusations of meat theft, mate competition, and rumor spreading. They also compete with members of their social network and with those who were designated as cooperative helpers or as close kin. Women take fewer beads from desired friends, neighbors, and from those viewed as enemies. We interpret favoritism toward enemies as resulting from fear of retribution. Our results suggest that social relations among women are multifaceted and often cannot be simplified by exclusive focus on genetic relatedness, physical proximity, or reciprocity. We argue that a complex understanding of cooperation and competition among women may require important contextual information concerning relationship history in addition to typical features of resource ecology

Aging and Inflammation in Two Epidemiological Worlds

Humans evolved in a world with high levels of infection resulting in high mortality across the life span and few survivors to advanced ages. Under such conditions, a strong acute-phase inflammatory response was required for survival; however, inflammatory responses can also promote chronic diseases of aging. We hypothesize that global historical increases in life span at older ages are partly explained by reduced lifetime exposure to infection and subsequent inflammation. To begin a test of this hypothesis, we compare C-reactive protein (CRP); levels in two populations with different epidemiological environments: the Tsimane of Bolivia and persons in the United States. High CRP is significantly more prevalent among the Tsimane up through middle age; by age 35, the Tsimane have spent more years with high CRP than have Americans at age 55. Further testing of the links among infection, inflammation, and chronic diseases of aging among the Tsimane requires collection of age-specific indicators of atherosclerosis and cardiac function

Inflammation and Infection Do Not Promote Arterial Aging and Cardiovascular Disease Risk Factors Among Lean Horticulturalists

Background: Arterial aging is well characterized in industrial populations, but scantly described in populations with little access to modern medicine. Here we characterize health and aging among the Tsimane, Amazonian forager-horticulturalists with short life expectancy, high infectious loads and inflammation, but low adiposity and robust physical fitness. Inflammation has been implicated in all stages of arterial aging, atherogenesis and hypertension, and so we test whether greater inflammation associates with atherosclerosis and CVD risk. In contrast, moderate to vigorous daily activity, minimal obesity, and low fat intake predict minimal CVD risk among older Tsimane. Methods and Findings: Peripheral arterial disease (PAD), based on the Ankle-Brachial Index (ABI), and hypertension were measured in Tsimane adults, and compared with rates from industrialized populations. No cases of PAD were found among Tsimane and hypertension was comparatively low (prevalence: 3.5%, 40+; 23%, 70+). Markers of infection and inflammation were much higher among Tsimane than among U.S. adults, whereas HDL was substantially lower. Regression models examine associations of ABI and BP with biomarkers of energy balance and metabolism and of inflammation and infection. Among Tsimane, obesity, blood lipids, and disease history were not significantly associated with ABI. Unlike the Tsimane case, higher cholesterol, C-reactive protein, leukocytes, cigarette smoking and systolic pressure among North Americans are all significantly associated with lower ABI. Conclusions: Inflammation may not always be a risk factor for arterial degeneration and CVD, but instead may be offset by other factors: healthy metabolism, active lifestyle, favorable body mass, lean diet, low blood lipids and cardiorespiratory health. Other possibilities, including genetic susceptibility and the role of helminth infections, are discussed. The absence of PAD and CVD among Tsimane parallels anecdotal reports from other small-scale subsistence populations and suggests that chronic vascular disease had little impact on adult mortality throughout most of human evolutionary history

Inflammation and Infection Do Not Promote Arterial Aging and Cardiovascular Disease Risk Factors among Lean Horticulturalists

BACKGROUND: Arterial aging is well characterized in industrial populations, but scantly described in populations with little access to modern medicine. Here we characterize health and aging among the Tsimane, Amazonian forager-horticulturalists with short life expectancy, high infectious loads and inflammation, but low adiposity and robust physical fitness. Inflammation has been implicated in all stages of arterial aging, atherogenesis and hypertension, and so we test whether greater inflammation associates with atherosclerosis and CVD risk. In contrast, moderate to vigorous daily activity, minimal obesity, and low fat intake predict minimal CVD risk among older Tsimane. METHODS AND FINDINGS: Peripheral arterial disease (PAD), based on the Ankle-Brachial Index (ABI), and hypertension were measured in Tsimane adults, and compared with rates from industrialized populations. No cases of PAD were found among Tsimane and hypertension was comparatively low (prevalence: 3.5%, 40+; 23%, 70+). Markers of infection and inflammation were much higher among Tsimane than among U.S. adults, whereas HDL was substantially lower. Regression models examine associations of ABI and BP with biomarkers of energy balance and metabolism and of inflammation and infection. Among Tsimane, obesity, blood lipids, and disease history were not significantly associated with ABI. Unlike the Tsimane case, higher cholesterol, C-reactive protein, leukocytes, cigarette smoking and systolic pressure among North Americans are all significantly associated with lower ABI. CONCLUSIONS: Inflammation may not always be a risk factor for arterial degeneration and CVD, but instead may be offset by other factors: healthy metabolism, active lifestyle, favorable body mass, lean diet, low blood lipids and cardiorespiratory health. Other possibilities, including genetic susceptibility and the role of helminth infections, are discussed. The absence of PAD and CVD among Tsimane parallels anecdotal reports from other small-scale subsistence populations and suggests that chronic vascular disease had little impact on adult mortality throughout most of human evolutionary history

Exploring the Great Schism in the Social Sciences: Confirmation Bias and the Interpretation of Results Relating to Biological Influences on Human Behavior and Psychology

The nature–nurture debate is one that biologists often dismiss as a false dichotomy, as all phenotypic traits are the results of complex processes of gene and environment interactions. However, such dismissiveness belies the ongoing debate that is unmistakable throughout the biological and social sciences concerning the role of biological influences in the development of psychological and behavioral traits in humans. Many have proposed that this debate is due to ideologically driven biases in the interpretation of results. Those favoring biological approaches have been accused of a greater willingness to accept biological explanations so as to rationalize or justify the status quo of inequality. Those rejecting biological approaches have been accused of an unwillingness to accept biological explanations so as to attribute inequalities solely to social and institutional factors, ultimately allowing for the possibility of social equality. While it is important to continue to investigate this topic through further research and debate, another approach is to examine the degree to which the allegations of bias are indeed valid. To accomplish this, a convenience sample of individuals with relevant postgraduate degrees was recruited from Mechanical Turk and social media. Participants were asked to rate the inferential power of different research designs and of mock results that varied in the degree to which they supported different ideologies. Results were suggestive that researchers harbor sincere differences of opinion concerning the inferential value of relevant research. There was no suggestion that ideological confirmation biases drive these differences. However, challenges associated with recruiting a large enough sample of experts as well as identifying believable mock scenarios limit the study’s inferential scope

Tests of Hypotheses.

<p>Tests of Hypotheses.</p