Triadic influence as a proxy for compatibility in social relationships.

Networks of social interactions are the substrate upon which civilizations are built. Often, we create new bonds with people that we like or feel that our relationships are damaged through the intervention of third parties. Despite their importance and the huge impact that these processes have in our lives, quantitative scientific understanding of them is still in its infancy, mainly due to the difficulty of collecting large datasets of social networks including individual attributes. In this work, we present a thorough study of real social networks of 13 schools, with more than 3,000 students and 60,000 declared positive and negative relationships, including tests for personal traits of all the students. We introduce a metric-the "triadic influence"-that measures the influence of nearest neighbors in the relationships of their contacts. We use neural networks to predict the sign of the relationships in these social networks, extracting the probability that two students are friends or enemies depending on their personal attributes or the triadic influence. We alternatively use a high-dimensional embedding of the network structure to also predict the relationships. Remarkably, using the triadic influence (a simple one-dimensional metric) achieves the best accuracy, and adding the personal traits of the students does not improve the results, suggesting that the triadic influence acts as a proxy for the social compatibility of students. We postulate that the probabilities extracted from the neural networks-functions of the triadic influence and the personalities of the students-control the evolution of real social networks, opening an avenue for the quantitative study of these systems.

Parents' knowledge and predictions about the age of menarche: experimental evidence from Honduras.

BACKGROUND: Access to accurate, timely and age-appropriate information about menarche is an essential part of menstrual health. Reliable evidence shows that girls primarily obtain information from their mothers and/or other female family members, therefore, it is important to determine parents' knowledge and their predictions about other parents' knowledge of the age of menarche. METHODS: To this end, we performed a pre-registered study with data collected from 360 households in Santa Rosa de Copán, Honduras. We implemented a novel procedure to avoid social desirability bias whereby participants answered two separated questions: i) their knowledge about the age of menarche (self-report) and ii) to predict or guess the modal response of the other participants regarding the same question (modal guess). Participants were paid according to accuracy. Both questions appeared randomly in the survey. RESULTS: Recent studies indicate the age of menarche at 12 years old and 56.11% of the sample gave the same response while 62.78% hit the modal value. We estimated the impact of different sociodemographic variables and found only marginal differences. Interestingly, people with formal education and women tend to respond with lower predictions. CONCLUSION: Parents' knowledge about the age of menarche is high in the study area. The study also found that there was no social desirability bias.

Continuous and binary sets of responses differ in the field.

This paper conducts a pre-registered study aimed to compare binary and continuous set of responses in survey questionnaires. Binary responses consist of two possible opposing response options (Yes/No). Continuous responses are numerical, where respondents can indicate an option on a 0-10 horizontal blind line. We study whether feasible sets of binary and continuous responses yield the same outcome (distribution) and have the same cost (duration in minutes). We collect data from 360 households in Honduras that were randomly assigned to Yes/No questions or given a slider (0-10 visual scale) to mark their responses, therefore, we provide causal evidence. We find that respondents are 13% more likely to respond "Yes" and spend 2.1 min less in the binary setting. Additionally, the results suggest that the type of question matters.

Culture and group-functional punishment behaviour.

Humans often 'altruistically' punish non-cooperators in one-shot interactions among genetically unrelated individuals. This poses an evolutionary puzzle because altruistic punishment enforces cooperation norms that benefit the whole group but is costly for the punisher. One key explanation is that punishment follows a social-benefits logic: it is eminently normative and group-functional (drawing on cultural group selection theories). In contrast, mismatch-based deterrence theory argues that punishment serves the individual-level function of deterring mistreatment of oneself and one's allies, hinging upon the evolved human coalitional psychology. We conducted multilateral-cooperation experiments with a sample of Spanish Romani people (Gitanos or Calé) and the non-Gitano majority. The Gitanos represent a unique case study because they rely heavily on close kin-based networks and display a strong ethnic identity. We find that Gitano non-cooperators were not punished by co-ethnics in only-Gitano (ethnically) homogeneous groups but were harshly punished by other Gitanos and by non-Gitanos in ethnically mixed groups. Our findings suggest the existence of culture-specific motives for punishment: Gitanos, especially males, appear to use punishment to protect their ethnic identity, whereas non-Gitanos use punishment to protect a norm of universal cooperation. Only theories that consider normative, group-functional forces underlying punishment behaviour can explain our data.

Hyper-altruistic behavior vanishes with high stakes.

Using an incentivized experiment with statistical power, this paper explores the role of stakes in charitable giving of lottery prizes, where subjects commit to donate a fraction of the prize before they learn the outcome of the lottery. We study three stake levels: 5€ (n = 177), 100€ (n = 168), and 1,000€ (n = 171). Although the donations increase in absolute terms as the stakes increase, subjects decrease the donated fraction of the pie. However, people still share roughly 20% of 1,000€, an amount as high as the average monthly salary of people at the age of our subjects. The number of people sharing 50% of the pie is remarkably stable across stakes, but donating the the whole pie-the modal behavior in charity-donation experiments-disappears with stakes. Such hyper-altruistic behavior thus seems to be an artifact of the stakes typically employed in economic and psychological experiments. Our findings point out that sharing with others is a prevalent human feature, but stakes are an important determinant of sharing. Policies promoted via prosocial frames (e.g., stressing the effects of mask-wearing or social distancing on others during the Covid-19 pandemic or environmentally-friendly behaviors on future generations) may thus be miscalibrated if they disregard the stakes at play.

Digit ratio (2D : 4D) and prosocial behaviour in economic games: no direct correlation with generosity, bargaining or trust-related behaviours.

Prenatal exposure to sex hormones exerts organizational effects on the brain which have observable behavioural correlates in adult life. There are reasons to expect that social behaviours-fundamental for the evolutionary success of humans-might be related to biological factors such as prenatal sex hormone exposure. Nevertheless, the existing literature is inconclusive as to whether and how prenatal exposure to testosterone and oestrogen, proxied by the second-to-fourth digit ratio (2D : 4D), may predict non-selfish behaviour. Here, we investigate this question using economic experiments with real monetary stakes and analyse five different dimensions of social behaviour in a comparatively large sample of Caucasian participants (n = 560). For both males and females, our results show no robust association between right- or left-hand 2D : 4D and generosity, bargaining or trust-related behaviours. Moreover, no differences in behaviour were found according to sex. We conclude that there is no direct correlation between 2D : 4D and these social behaviours.

The emergence of altruism as a social norm.

Expectations, exerting influence through social norms, are a very strong candidate to explain how complex societies function. In the Dictator game (DG), people expect generous behavior from others even if they cannot enforce any sharing of the pie. Here we assume that people donate following their expectations, and that they update their expectations after playing a DG by reinforcement learning to construct a model that explains the main experimental results in the DG. Full agreement with the experimental results is reached when some degree of mismatch between expectations and donations is added into the model. These results are robust against the presence of envious agents, but affected if we introduce selfish agents that do not update their expectations. Our results point to social norms being on the basis of the generous behavior observed in the DG and also to the wide applicability of reinforcement learning to explain many strategic interactions.

Humans expect generosity.

Mechanisms supporting human ultra-cooperativeness are very much subject to debate. One psychological feature likely to be relevant is the formation of expectations, particularly about receiving cooperative or generous behavior from others. Without such expectations, social life will be seriously impeded and, in turn, expectations leading to satisfactory interactions can become norms and institutionalize cooperation. In this paper, we assess people's expectations of generosity in a series of controlled experiments using the dictator game. Despite differences in respective roles, involvement in the game, degree of social distance or variation of stakes, the results are conclusive: subjects seldom predict that dictators will behave selfishly (by choosing the Nash equilibrium action, namely giving nothing). The majority of subjects expect that dictators will choose the equal split. This implies that generous behavior is not only observed in the lab, but also expected by subjects. In addition, expectations are accurate, matching closely the donations observed and showing that as a society we have a good grasp of how we interact. Finally, correlation between expectations and actual behavior suggests that expectations can be an important ingredient of generous or cooperative behavior.

Self-identified Obese People Request Less Money: A Field Experiment.

Empirical evidence suggests that obese people are discriminated in different social environments, such as the work place. Yet, the degree to which obese people are internalizing and adjusting their own behavior as a result of this discriminatory behavior has not been thoroughly studied. We develop a proxy for measuring experimentally the "self-weight bias" by giving to both self-identified obese (n = 90) and non-obese (n = 180) individuals the opportunity to request a positive amount of money after having performed an identical task. Consistent with the System Justification Theory, we find that self-identified obese individuals, due to a preexisting false consciousness, request significantly lower amounts of money than non-obese ones. A within subject comparison between self-reports and external monitors' evaluations reveals that the excessive weight felt by the "self" but not reported by evaluators captures the self-weight bias not only for obese but also for non-obese individuals. Linking our experimental results to the supply side of the labor market, we argue that self-weight bias, as expressed by lower salary requests, enhances discriminatory behavior against individuals who feel, but may not actually be, obese and consequently exacerbates the wage gap across weight.

BMI is not related to altruism, fairness, trust or reciprocity: Experimental evidence from the field and the lab.

Over the past few decades obesity has become one of the largest public policy concerns among the adult population in the developed world. Obesity and overweight are hypothesized to affect individuals' sociability through a number of channels, including discrimination and low self-esteem. However, whether these effects translate into differential behavioural patterns in social interactions remains unknown. In two large-scale economic experiments, we explore the relationship between Body Mass Index (BMI) and social behaviour, using three paradigmatic economic games: the dictator, ultimatum, and trust games. Our first experiment employs a representative sample of a Spanish city's population (N=753), while the second employs a sample of university students from the same city (N=618). Measures of altruism, fairness/equality, trust and reciprocity are obtained from participants' experimental decisions. Using a variety of regression specifications and control variables, our results suggest that BMI does not exert an effect on any of these social preferences. Some implications of these findings are discussed.

Short- and long-run goals in ultimatum bargaining: impatience predicts spite-based behavior.

The ultimatum game (UG) is widely used to study human bargaining behavior and fairness norms. In this game, two players have to agree on how to split a sum of money. The proposer makes an offer, which the responder can accept or reject. If the responder rejects, neither player gets anything. The prevailing view is that, beyond self-interest, the desire to equalize both players' payoffs (i.e., fairness) is the crucial motivation in the UG. Based on this view, previous research suggests that fairness is a short-run oriented motive that conflicts with the long-run goal of self-interest. However, competitive spite, which reflects an antisocial (not norm-based) desire to minimize others' payoffs, can also account for the behavior observed in the UG, and has been linked to short-run, present-oriented aspirations as well. In this paper, we explore the relationship between individuals' intertemporal preferences and their behavior in a citywide dual-role UG experiment (N = 713). We find that impatience (short-run orientation) predicts the rejection of low, "unfair" offers as responder and the proposal of low, "unfair" offers as proposer, which is consistent with spitefulness but inconsistent with fairness motivations. This behavior systematically reduces the payoffs of those who interact with impatient individuals. Thus, impatient individuals appear to be keen to minimize their partners' share of the pie, even at the risk of destroying it. These findings indicate that competitively reducing other's payoffs, rather than fairness (or self-interest), is the short-run goal in ultimatum bargaining.

Fair and unfair punishers coexist in the Ultimatum Game.

In the Ultimatum Game, a proposer suggests how to split a sum of money with a responder. If the responder rejects the proposal, both players get nothing. Rejection of unfair offers is regarded as a form of punishment implemented by fair-minded individuals, who are willing to impose the cooperation norm at a personal cost. However, recent research using other experimental frameworks has observed non-negligible levels of antisocial punishment by competitive, spiteful individuals, which can eventually undermine cooperation. Using two large-scale experiments, this note explores the nature of Ultimatum Game punishers by analyzing their behavior in a Dictator Game. In both studies, the coexistence of two entirely different sub-populations is confirmed: prosocial punishers on the one hand, who behave fairly as dictators, and spiteful (antisocial) punishers on the other, who are totally unfair. The finding has important implications regarding the evolution of cooperation and the behavioral underpinnings of stable social systems.

Religious pro-sociality? Experimental evidence from a sample of 766 Spaniards.

This study explores the relationship between several personal religion-related variables and social behaviour, using three paradigmatic economic games: the dictator (DG), ultimatum (UG), and trust (TG) games. A large carefully designed sample of the urban adult population in Granada (Spain) is employed (N = 766). From participants' decisions in these games we obtain measures of altruism, bargaining behaviour and sense of fairness/equality, trust, and positive reciprocity. Three dimensions of religiosity are examined: (i) religious denomination; (ii) intensity of religiosity, measured by active participation at church services; and (iii) conversion out into a different denomination than the one raised in. The major results are: (i) individuals with "no religion" made decisions closer to rational selfish behaviour in the DG and the UG compared to those who affiliate with a "standard" religious denomination; (ii) among Catholics, intensity of religiosity is the key variable that affects social behaviour insofar as religiously-active individuals are generally more pro-social than non-active ones; and (iii) the religion raised in seems to have no effect on pro-sociality, beyond the effect of the current measures of religiosity. Importantly, behaviour in the TG is not predicted by any of the religion-related variables we analyse. While the results partially support the notion of religious pro-sociality, on the other hand, they also highlight the importance of closely examining the multidimensional nature of both religiosity and pro-social behaviour.

Can exposure to prenatal sex hormones (2D:4D) predict cognitive reflection?

The Cognitive Reflection Test (CRT) is a test introduced by Frederick (2005). The task is designed to measure the tendency to override an intuitive response that is incorrect and to engage in further reflection that leads to the correct response. The consistent sex differences in CRT performance may suggest a role for prenatal sex hormones. A now widely studied putative marker for relative prenatal testosterone is the second-to-fourth digit ratio (2D:4D). This paper tests to what extent 2D:4D, as a proxy for the prenatal ratio of testosterone/estrogens, can predict CRT scores in a sample of 623 students. After controlling for sex, we observe that a lower 2D:4D (reflecting a relative higher exposure to testosterone) is significantly associated with a higher number of correct answers. The result holds for both hands' 2D:4Ds. In addition, the effect appears to be stronger for females than for males. We also control for patience and math proficiency, which are significantly related to performance in the CRT. But the effect of 2D:4D on performance in CRT is not reduced with these controls, implying that these variables are not mediating the relationship between digit ratio and CRT.

Second-to-fourth digit ratio has a non-monotonic impact on altruism.

Gene-culture co-evolution emphasizes the joint role of culture and genes for the emergence of altruistic and cooperative behaviors and behavioral genetics provides estimates of their relative importance. However, these approaches cannot assess which biological traits determine altruism or how. We analyze the association between altruism in adults and the exposure to prenatal sex hormones, using the second-to-fourth digit ratio. We find an inverted U-shaped relation for left and right hands, which is very consistent for men and less systematic for women. Subjects with both high and low digit ratios give less than individuals with intermediate digit ratios. We repeat the exercise with the same subjects seven months later and find a similar association, even though subjects' behavior differs the second time they play the game. We then construct proxies of the median digit ratio in the population (using more than 1000 different subjects), show that subjects' altruism decreases with the distance of their ratio to these proxies. These results provide direct evidence that prenatal events contribute to the variation of altruistic behavior and that the exposure to fetal hormones is one of the relevant biological factors. In addition, the findings suggest that there might be an optimal level of exposure to these hormones from social perspective.

Experimental subjects are not different.

Experiments using economic games are becoming a major source for the study of human social behavior. These experiments are usually conducted with university students who voluntarily choose to participate. Across the natural and social sciences, there is some concern about how this "particular" subject pool may systematically produce biased results. Focusing on social preferences, this study employs data from a survey-experiment conducted with a representative sample of a city's population (N = 765). We report behavioral data from five experimental decisions in three canonical games: dictator, ultimatum and trust games. The dataset includes students and non-students as well as volunteers and non-volunteers. We separately examine the effects of being a student and being a volunteer on behavior, which allows a ceteris paribus comparison between self-selected students (students*volunteers) and the representative population. Our results suggest that self-selected students are an appropriate subject pool for the study of social behavior.

Patient and impatient punishers of free-riders.

Costly punishment of cheaters who contribute little or nothing to a cooperating group has been extensively studied, as an effective means to enforce cooperation. The prevailing view is that individuals use punishment to retaliate against transgressions of moral standards such as fairness or equity. However, there is much debate regarding the psychological underpinnings of costly punishment. Some authors suggest that costly punishment must be a product of humans' capacity for reasoning, self-control and long-term planning, whereas others argue that it is the result of an impulsive, present-oriented emotional drive. Here, we explore the inter-temporal preferences of punishers in a multilateral cooperation game and show that both interpretations might be right, as we can identify two different types of punishment: punishment of free-riders by cooperators, which is predicted by patience (future orientation); and free-riders' punishment of other free-riders, which is predicted by impatience (present orientation). Therefore, the picture is more complex as punishment by free-riders probably comes not from a reaction against a moral transgression, but instead from a competitive, spiteful drive. Thus, punishment grounded on morals may be related to lasting or delayed psychological incentives, whereas punishment triggered by competitive desires may be linked to short-run aspirations. These results indicate that the individual's time horizon is relevant for the type of social behaviour she opts for. Integrating such differences in inter-temporal preferences and the social behaviour of agents might help to achieve a better understanding of how human cooperation and punishment behaviour has evolved.

Economía experimental y del comportamiento / No disponible

A diferencia de la Psicología, la Economía no comenzó a experimentar hasta fechas muy recientes. Aprovechando las principales ventajas de la experimentación (la replicabilidad y el control) la Economía ha sido capaz de contrastar las teorías existentes y de aportar nueva evidencia que nos ha servido para desarrollar nuevos modelos de comportamiento humano. Este artículo hace un esbozo del origen y de lo que es en la actualidad la Economía Experimental y la Economía del Comportamiento. Además se presenta un repaso detallado de dos temas que han sido objeto de investigación en nuestro país, intentando resaltar aquellos desarrollos que guardan una mayor relación con la psicología: lo modelos de jerarquías cognitivas y las preferencias sociales (AU)

Unlike Psychology, laboratory experiments in Economics are quite recent. Taking advantage of the main virtues of experiments (replicability and control), Economics researchers have been able to test existing theory and contribute new evidence to the development of new models of human behavior. This paper provides a short review of the origins and some of the topics of interest for Experimental Economics and Behavioral Economics. Special attention is paid to the areas where Spanish experimentalists have been more influential, highlighting those more closely related to Psychology: cognitive hierarchies and social preferences (AU)

Organizing effects of testosterone and economic behavior: not just risk taking.

Recent literature emphasizes the role that testosterone, as well as markers indicating early exposure to T and its organizing effect on the brain (such as the ratio of second to fourth finger, [Formula: see text]), have on performance in financial markets. These results may suggest that the main effect of T, either circulating or in fetal exposure, on economic behavior occurs through the increased willingness to take risks. However, these findings indicate that traders with a low digit ratio are not only more profitable, but more able to survive in the long run, thus the effect might consist of more than just lower risk aversion. In addition, recent literature suggests a positive correlation between abstract reasoning ability and higher willingness to take risks. To test the two hypotheses of testosterone on performance in financial activities (effect on risk attitude versus a complex effect involving risk attitude and reasoning ability), we gather data on the three variables in a sample of 188 ethnically homogeneous college students (Caucasians). We measure a [Formula: see text] digit ratio, abstract reasoning ability with the Raven Progressive Matrices task, and risk attitude with choice among lotteries. Low digit ratio in men is associated with higher risk taking and higher scores in abstract reasoning ability when a combined measure of risk aversion over different tasks is used. This explains both the higher performance and higher survival rate observed in traders, as well as the observed correlation between abstract reasoning ability and risk taking. We also analyze how much of the total effect of digit ratio on risk attitude is direct, and how much is mediated. Mediation analysis shows that a substantial part of the effect of T on attitude to risk is mediated by abstract reasoning ability.