Unraveling public good games

This paper provides experimental evidence on how players predict end-game effects in a linear public good game. Our regression analysis yields a measure of the relative importance of priors and signals on subjects’ beliefs on contributions and allows us to conclude that, first, the weight of the signal is relatively unimportant, while priors have a large weight and, second, priors are the same for all periods. Hence, subjects do not expect end-game effects and there is very little updating of beliefs. We argue that the sustainability of cooperation is related to this pattern of belief formation

Time discounting and pain anticipation: experimental evidence

This paper deals with pain anticipation experienced before medical procedures. Our experimental results show that individuals with lower time discount factors are more prone to suffer pain in advance. We provide a framework to rationalize the connection between pain anticipation and impatience. In this set up, more impatient subjects, who only value very near events, mainly take into account the present negative effects of medical procedures (the costs), whereas more patient individuals have a net positive valuation of medical events,given that they are able to value both the cost incurred now and all the benefits to be accrued in the future

Experimental and self-reported measures of risk taking and digit ratio (2D:4D): evidence from a large, systematic study

Using a large (n=704) sample of laboratory subjects, we systematically investigate the links between the digit ratio - a biomarker for pre-natal testosterone exposure - and two measures of individual risk taking: (i) risk preferences over lotteries with real monetary incentives, and (ii) self-reported risk attitude. The digit ratio (also called 2D:4D) is the ratio of the length of the index finger to the length of the ring finger, and we consider both hands’ digit ratios. Previous studies have found that the digit ratio correlates with risk taking in some subject samples, but not others. In our sample, we find that both the right-hand and the left-hand digit ratio are significantly associated with risk preferences: subjects with lower digit ratios tend to choose riskier lotteries. Neither digit ratio, however, is associated with self-reported risk attitude

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 when they cannot enforce any sharing of the pie. Here we assume that people donate following their expectations, and that they update their expectation 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

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

Strategic risk and response time across games

Experimental data for two types of bargaining games are used to study the role of strategic risk in the decision making process that takes place when subjects play a game only once. The bargaining games are the Ultimatum Game (UG) and the Yes-or-No Game (YNG). Strategic risk in a game stems from the effect on one player’s payoff of the behavior of other players. In the UG this risk is high, while it is nearly absent in the YNG. In studying the decision making process of subjects we use the time elapsed before a choice is made (response time) as a proxy for amount of thought or introspection. We find that response times are on average larger in the UG than in the YNG, indicating a positive correlation between strategic risk and introspection. In both games the behavior of subjects with large response times is more dispersed than that of subjects with small response times. In the UG larger response time is associated with less generous and thus riskier behavior, while it is associated to more generous behavior in the YNG

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

Digit ratio (2D:4D) and social integration: an effect of prenatal sex hormones

The position people occupy in their social and professional networks is related to their social status and has strong effects on their access to social resources. While attainment of particular positions is driven by behavioral traits, many biological factors predispose individuals to certain behaviors and motivations. Prior work on exposure to fetal androgens (measured by second-to-fourth digit ratio, 2D:4D) shows that it correlates with behaviors and traits related to social status, which might make people more socially integrated. However, it also predicts certain anti-social behaviors and disorders associated with lower socialization. We explore whether 2D:4D correlates with network position later in life and find that individuals with low 2D:4D become more central in their social environment. Interestingly, low 2D:4D males are more likely to exhibit high betweenness centrality (they connect separated parts of the social structure) while low 2D:4D females are more likely to exhibit high in-degree centrality (more people name them as friends). These gender-specific differences are reinforced by transitivity (the likelihood that one’s friends are also friends with one another): neighbors of low 2D:4D men tend not to know each other; the contrary is observed for low 2D:4D women. Our results suggest that biological predispositions influence the organization of human societies and that exposure to prenatal androgens influences different status seeking behaviors in men and women