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The present investigation provides the first systematic empirical tests for the role of politics in academic research. In a large sample of scientific abstracts from the field of social psychology, we find both evaluative differences, such that conservatives are described more negatively than liberals, and explanatory differences, such that conservatism is more likely to be the focus of explanation than liberalism. In light of the ongoing debate about politicized science, a forecasting survey permitted scientists to state a priori empirical predictions about the results, and then change their beliefs in light of the evidence. Participating scientists accurately predicted the direction of both the evaluative and explanatory differences, but at the same time significantly overestimated both effect sizes. Scientists also updated their broader beliefs about political bias in response to the empirical results, providing a model for addressing divisive scientific controversies across fields.

"We propose to change the default P-value threshold forstatistical significance for claims of new discoveries from 0.05 to 0.005."

We measure how accurately replication of experimental results can be predicted by a black-box statistical model. With data from four large- scale replication projects in experimental psychology and economics, and techniques from machine learning, we train a predictive model and study which variables drive predictable replication.The model predicts binary replication with a cross validated accuracy rate of 70% (AUC of 0.79) and relative effect size with a Spearman ρ of 0.38. The accuracy level is similar to the market-aggregated beliefs of peer scientists (Camerer et al., 2016; Dreber et al., 2015). The predictive power is validated in a pre-registered out of sample test of the outcome of Camerer et al. (2018b), where 71% (AUC of 0.73) of replications are predicted correctly and effect size correlations amount to ρ = 0.25.Basic features such as the sample and effect sizes in original papers, and whether reported effects are single-variable main effects or two- variable interactions, are predictive of successful replication. The models presented in this paper are simple tools to produce cheap, prognostic replicability metrics. These models could be useful in institutionalizing the process of evaluation of new findings and guiding resources to those direct replications that are likely to be most informative.

Recent large-scale replications of social science experiments provide important information on the reliability of experimental research. Unfortunately, there exist no mechanisms to ensure replications are done. We propose such a mechanism: journal-based replication, in which the publishing journal contracts for a replication between acceptance and publication. We discuss what we learned from a proof-of-concept journal-based replication at the Journal of Public Economics. Our experience indicates that journal-based replication would be relatively straightforward to implement for laboratory experiments.

Experimental results from student or other non-representative convenience samples often suggest that men, on average, are more risk-taking and competitive than women. Here we explore whether these gender preference gaps also exist in a simple random sample of the Swedish adult population. Our design comprises four different treatments to systematically explore how the experimental context may impact gender gaps; a baseline treatment, a treatment where participants are primed with their own gender, and a treatment where the participants know the gender of their counterpart (man or woman). We look at willingness to compete in two domains: a math task and a verbal task. We find no gender differences in risk preferences or in willingness to compete in the verbal task in this random sample. There is some support for men being more competitive than women in the math task, in particular in the pooled sample. The effect size is however considerably smaller than what is typically found. We further find no consistent impact of treatment on (the absence of) the gender gap in preferences. JEL codes: D91, C83, C91

Women are often less willing than men to compete, even in tasks where there is no gender gap in performance. Also, many people experience competitive contexts as stressful and previous research has documented that men and women sometimes react differently to acute stressors. We use two laboratory experiments to investigate whether factors related to stress can help explain the gender gap in competitiveness. Experiment 1 studies whether stress responses (measured with salivary cortisol and through self-assessment) to taking part in a mandatory competition predict individual willingness to participate in a voluntary competition. We find that while the mandatory competition does increase stress levels, there is no gender difference in this reaction. Cortisol response does not predict willingness to compete for men but is positively and significantly correlated with choosing to enter the voluntary competition for women. In Experiment 2 we exogenously induce stress using the cold-pressor task. We find no causal effect of stress on competitiveness for the sample as a whole and only tentative evidence of a positive effect for women. In summary, even though there are some gender differences in the relation between stress responses and the decision to enter a competition or not, these cannot explain the general gender gap in willingness to compete that is generally found in the literature and which we replicate.

We look at gender differences among adolescents in Sweden in preferences for competition, altruism and risk. For competitiveness, we explore two different tasks that differ in associated stereotypes. We find no gender difference in competitiveness when comparing performance under competition to that without competition. We further find that boys and girls are equally likely to self-select into competition in a verbal task, but that boys are significantly more likely to choose to compete in a mathematical task. This gender gap diminishes and becomes non-significant when we control for actual performance and beliefs about relative performance. These results show that among adolescents in our sample, the gender gap in competitiveness is not due to preferences for competition per se. Girls are also more altruistic and less risk taking than boys.

We look at gender differences among adolescents in Sweden in preferences for altruism, risk and competition. We find that girls are more altruistic and less risk taking than boys. No gender differences are found comparing competitive performance with non-competitive performance in either a verbal or a mathematical task. Boys and girls are also equally likely to self-select into competition in the verbal task, but boys are significantly more likely to choose to compete in math. However, this gender gap diminishes and becomes non-significant when we control for performance beliefs relative to others, indicating that some of the gender gap in our sample is not due to preferences for competition per se.

Background: Recent evidence suggests that individual variation in risk taking is partly due to genetic factors. Methodology/Principal Findings: We explore how self-reported risk taking in different domains correlates with variation in the dopamine receptor D4 gene (DRD4). Past studies conflict on the influence of DRD4 in relation to risk taking. A sample of 237 serious tournament contract bridge players, experts on risk taking in one domain, was genotyped for having a 7-repeat allele (7R+) or not (7R-) at DRD4. No difference was found between 7R+ and 7R- individuals in general risk taking or in several other risk-related activities. Conclusion: In this sample of individuals (tournament bridge players) there is no relationship between DRD4 genotype and self-reported risk taking in different domains.

We compare how children aged 9-12 in Colombia and Sweden cooperate in a Prisoner's Dilemma. We introduce a new measurement device for cooperation that can be easily understood by children. There is some evidence of more cooperation in Sweden than in Colombia. Girls in Colombia are less cooperative than boys, whereas our results indicate the opposite in Sweden. Girls are in general more cooperative with boys than with girls. Relating cooperation to competitiveness, this appears to be task and country dependent.

Many previous experiments document that behavior in multi-person settings responds to the name of the game and the labeling of strategies. Usually these studies cannot tell whether frames affect preferences or beliefs. In this Dictator game study, we investigate whether social framing effects are also present when only one of the subjects makes a decision, in which case the frame may only affect preferences. We find that behavior is insensitive to social framing.

Education has important short and long run implications for individual outcomes. In this paper we explore the association between age at pubertal onset and educational outcomes in a sample of Swedish girls. Previous research suggests that girls that mature earlier perform worse in school compared to girls that mature later. To test if this is also true among Swedish girls, we investigate the association between pubertal development and grades, educational aspirations and educational choice. We also investigate whether changes in risk attitudes, time preferences and priorities concerning school versus friends mediate this potential correlation. We confirm that earlier maturing girls have lower grades and lower educational aspirations, but find that they make educational choices similar to those of later maturing girls. Furthermore, we do not find that these differences in grades and aspirations are mediated by risk attitudes, time preferences or priorities

Individuals differ significantly in their willingness to take risks. Such differences may stem, at least in part, from individual biological (genetic) differences. We explore how risk-taking behavior correlates with different versions of the dopamine receptor D4 gene (DRD4), which has been implicated in previous studies of risk taking. We investigate risk taking in three contexts: economic risk taking as proxied by a financial gamble, self-reported general risk taking, and self-reported behavior in risk-related activities. Our participants are serious tournament bridge players with substantial experience in risk taking. Presumably, this sample is much less varied in its environment than a random sample of the population, making genetic based differences easier to detect. A prior study (Dreber et al. 2010) looked at risk taking by these individuals in their bridge decisions. Here we examine the riskiness of decisions they take in other contexts. We find evidence that individuals with a 7-repeat allele (7R+) of DRD4 take significantly more economic risk in an investment game than individuals without this allele (7R-). Interestingly, this positive relationship is driven by the men in our study, while the women show a negative but non-significant result. Even though the number of 7R+ women in our sample is low, our results may indicate a gender difference in how the 7R+ genotype affects behavior, a possibility that merits further study. Considering other risk measures, we find no difference between 7R+ and 7R- individuals in general risk taking or any of the risk-related activities. Overall, our results indicate that the dopamine system plays an important role in explaining individual differences in economic risk taking in men, but not necessarily in other activities involving risk.

We explore the relationship between attractiveness and risk taking in chess. We use a large international panel dataset on chess competitions which includes a control for the players' skill in chess. This data is combined with results from a survey on an online labor market where participants were asked to rate the photos of 626 expert chess players according to attractiveness. Our results suggest that male chess players choose significantly riskier strategies when playing against an attractive female opponent, even though this does not improve their performance. Women's strategies are not affected by the attractiveness of the opponent.

We designed an experiment that examines how knowledge about the price of a good, and the time at which the information is received, affects how the good is experienced. The good in question was wine, and the price was either high or low. Our results suggest that hosts offering wine to guests can safely reveal the price: much is gained if the wine is expensive, and little is lost if it is cheap. Disclosing the high price before tasting the wine produces considerably higher ratings, although only from women. Disclosing the low price, by contrast, does not result in lower ratings. Our finding supports the notion that price not only serves to clear markets, it also serves as a marketing tool; it influences expectations that in turn shape a consumer's experience. In addition, our results suggest that men and women respond differently to attribute information concerning wine.

Recent studies find that women are less competitive than men. This gender difference in competitiveness has been suggested as one possible explanation for why men occupy the majority of top positions in many sectors. In this study we explore competitiveness in children, with the premise that both culture and gendered stereotypes regarding the task at hand may influence competitive behavior. A related field experiment on Israeli children shows that only boys react to competition by running faster when competing in a race. We here test if there is a gender gap in running among 7-10 year old Swedish children. We also introduce two female sports, skipping rope and dancing, to see if competitiveness is task dependent. We find no gender difference in reaction to competition in any task; boys and girls compete equally. If gender equality matters for competitiveness, this result may be explained by cultural factors, since Sweden scores higher on gender equality indices than Israel.

Individuals who are unaware of the price do not derive more enjoyment from more expensive wine. In a sample of more than 6,000 blind tastings, we find that the correlation between price and overall rating is small and negative, suggesting that individuals on average enjoy more expensive wines slightly less. For individuals with wine training, however, we find indications of a positive, or at any rate non-negative, correlation. Our results are robust to the inclusion of individual fixed effects, and are not driven by outliers: when omitting the top and bottom deciles of the price distribution, our qualitative results are strengthened, and the statistical significance is improved even further. Our results indicate that both the prices of wines and wine recommendations by experts may be poor guides for non-expert wine consumers.