Person:

Dreber-Almenberg, Anna

We explore the extent to which altruism, as measured by giving in a dictator game (DG), accounts for play in a noisy version of the repeated prisoner's dilemma. We find that DG giving is correlated with cooperation in the repeated game when no cooperative equilibria exist, but not when cooperation is an equilibrium. Furthermore, none of the commonly observed strategies are better explained by inequity aversion or efficiency concerns than money maximization. Various survey questions provide additional evidence for the relative unimportance of social preferences. We conclude that cooperation in repeated games is primarily motivated by long-term payoff maximization and that even though some subjects may have other goals, this does not seem to be the key determinant of how play varies with the parameters of the repeated game. In particular, altruism does not seem to be a major source of the observed diversity of play.

People often favor members of their own group, while discriminating against members of other groups. Such in-group favoritism has been shown to play an important role in human cooperation. However, in the face of changing conflicts and shifting alliances, it is essential for group identities to be flexible. Using the dictator game from behavioral economics, we demonstrate the remodeling of group identities among supporters of Democratic presidential candidates Barack Obama and Hillary Clinton. After Clinton's concession in June 2008, Democrats were more generous toward supporters of their own preferred candidate than to supporters of the other Democratic candidate. The bias observed in June persisted into August, and disappeared only in early September after the Democratic National Convention. We also observe a strong gender effect, with bias both appearing and subsiding among men only. This experimental study illustrates a dynamic change in bias, tracking the realignment of real world conflict lines and public efforts to reconstitute group identity. The change in salient group identity we describe here likely contributed to the victory of Barack Obama in the 2008 presidential election.

Concerns about a lack of reproducibility of statistically significant results have recently been raised in many fields, and it has been argued that this lack comes at substantial economic costs. We here report the results from prediction markets set up to quantify the reproducibility of 44 studies published in prominent psychology journals and replicated in the Reproducibility Project: Psychology. The prediction markets predict the outcomes of the replications well and outperform a survey of market participants’ individual forecasts. This shows that prediction markets are a promising tool for assessing the reproducibility of published scientific results. The prediction markets also allow us to estimate probabilities for the hypotheses being true at different testing stages, which provides valuable information regarding the temporal dynamics of scientific discovery. We find that the hypotheses being tested in psychology typically have low prior probabilities of being true (median, 9%) and that a “statistically significant” finding needs to be confirmed in a well-powered replication to have a high probability of being true. We argue that prediction markets could be used to obtain speedy information about reproducibility at low cost and could potentially even be used to determine which studies to replicate to optimally allocate limited resources into replications.

Background: In a recent controversial essay, published by JPA Ioannidis in PLoS Medicine, it has been argued that in some research fields, most of the published findings are false. Based on theoretical reasoning it can be shown that small effect sizes, error-prone tests, low priors of the tested hypotheses and biases in the evaluation and publication of research findings increase the fraction of false positives. These findings raise concerns about the reliability of research. However, they are based on a very simple scenario of scientific research, where single tests are used to evaluate independent hypotheses. Methodology/Principal Findings: In this study, we present computer simulations and experimental approaches for analyzing more realistic scenarios. In these scenarios, research tasks are solved sequentially, i.e. subsequent tests can be chosen depending on previous results. We investigate simple sequential testing and scenarios where only a selected subset of results can be published and used for future rounds of test choice. Results from computer simulations indicate that for the tasks analyzed in this study, the fraction of false among the positive findings declines over several rounds of testing if the most informative tests are performed. Our experiments show that human subjects frequently perform the most informative tests, leading to a decline of false positives as expected from the simulations. Conclusions/Significance: For the research tasks studied here, findings tend to become more reliable over time. We also find that the performance in those experimental settings where not all performed tests could be published turned out to be surprisingly inefficient. Our results may help optimize existing procedures used in the practice of scientific research and provide guidance for the development of novel forms of scholarly communication.

Individuals differ significantly in their willingness to take risks, partly due to genetic differences. We explore how risk taking behavior correlates with different versions of the dopamine receptor D4 gene (DRD4). We focus on risk taking in the card game contract bridge, and economic risk taking as proxied by a financial gamble. We also explore self-reported general risk taking, and self-reported behavior in risk-related activities. Our participants are serious tournament bridge players, which gives them substantial experience in risk taking. We find some evidence that men with a 7-repeat allele (7R+) of DRD4 take more overall risk in bridge than individuals without this allele (7R-), and strong evidence that 7R+ men take more economic risk in an investment game. Interestingly, these relationships are not found in the women in our study. Although the number of 7R+ women in our sample is low, our results may reflect a gender difference in how the 7R+ genotype affects behavior. Bridge masterpoints measure past success, thus reflecting playing skill and experience. We show that masterpoint level modulates the effect of the DRD4 gene in men in a highly important manner. We find that higher ranked 7R+ men take significantly more good risks and significantly fewer bad risks than other men, whereas the opposite is found for less-expert 7R+ men. This is the first study to distinguish between advantageous and disadvantageous risk taking. We identify a strong interaction among desirable risk taking behavior, measured success, and genetic variation. Considering other risk measures, we find no difference between 7R+ and 7R- individuals in general risk taking or in any of a number of other risk-related activities. Our results indicate that the dopamine system plays an important role in explaining individual differences in risk taking in bridge and economic risk taking among men. Little relationship is found in other activities involving risk or among women.

Individuals differ significantly in their willingness to take risks, partly due to genetic differences. We explore how risk taking behavior correlates with different versions of the dopamine receptor D4 gene (DRD4). We focus on risk taking in the card game contract bridge, and economic risk taking as proxied by a financial gamble. We also explore self-reported general risk taking, and self-reported behavior in risk-related activities. Our participants are serious tournament bridge players, which gives them substantial experience in risk taking. We find some evidence that men with a 7-repeat allele (7R+) of DRD4 take more overall risk in bridge than individuals without this allele (7R-), and strong evidence that 7R+ men take more economic risk in an investment game. Interestingly, these relationships are not found in the women in our study. Although the number of 7R+ women in our sample is low, our results may reflect a gender difference in how the 7R+ genotype affects behavior. Bridge masterpoints measure past success, thus reflecting playing skill and experience. We show that masterpoint level modulates the effect of the DRD4 gene in men in a highly important manner. We find that higher ranked 7R+ men take significantly more good risks and significantly fewer bad risks than other men, whereas the opposite is found for less-expert 7R+ men. This is the first study to distinguish between advantageous and disadvantageous risk taking. We identify a strong interaction among desirable risk taking behavior, measured success, and genetic variation. Considering other risk measures, we find no difference between 7R+ and 7R- individuals in general risk taking or in any of a number of other risk-related activities. Our results indicate that the dopamine system plays an important role in explaining individual differences in risk taking in bridge and economic risk taking among men. Little relationship is found in other activities involving risk or among women.