Second Trimester Sunlight and Asthma: Evidence from Two Independent Studies

One in 12 Americans suffers from asthma, and its annual costs are estimated to exceed $50 billion. Yet the root causes of the disease remain unknown. A recent hypothesis posits that maternal vitamin D levels during pregnancy affect the probability the fetus later develops asthma. Employing two large-scale studies, we test this hypothesis using a natural experiment afforded by historical variation in sunlight, a major source of vitamin D. Specifically, holding the birth location and month fixed, we see how exogenous within-location variation in sunlight across birth years affects the probability of asthma onset. We show that this measurement of sunlight correlates with actual exposure, and consistent with preexisting results from the fetal development literature, we find substantial and highly significant evidence in both data sets that increased sunlight during the second trimester lowers the subsequent probability of asthma. Our results suggest policies designed to augment vitamin D levels in pregnant women, the large majority of whom are vitamin D insufficient, could be very cost effective and yield a substantial surplus

Dopamine and Risk Preferences in Different Domains

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.Risk preferences; Dopamine; Risk taking; Risk perception; DRD4

Dopamine and Risk Preferences in Different Domains

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 varies 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-related differences easier to detect. A prior study (Dreber et al. 2010) looked at risk taking by these individuals in their bridge decisions. We examine their risk decisions in other contexts. We find evidence that individuals with a 7-repeat allele (7R+) of the DRD4 genetic polymorphism 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.

The Dopamine Receptor D4 Gene (DRD4) and Self-Reported Risk Taking in the Economic Domain

Recent evidence suggests that individual variation in risk taking is partly due to genetic factors. 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 RD4. No difference was found between 7R+ and 7R- individuals in general risk taking or in several other risk-related activities.

Dynamic remodeling of in-group bias during the 2008 Presidential election

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

The Dopamine Receptor D4 Gene (DRD4) and Self-Reported Risk Taking in the Economic Domain

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

Dopamine and Risk Choices in Different Domains: Findings Among Series Tournament Bridge Players

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

Essays in applied microeconomics and networks

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Economics, 2016.Cataloged from PDF version of thesis.Includes bibliographical references (pages 153-167).Chapter 1 focuses on the recent dramatic shift in attitudes toward LGBT individuals in the U.S. and the accompanying rise in the number of Americans who have openly come out. We develop a model of stigma with Schelling-style tipping dynamics. Regions may be stuck in equilibria with low LGBT support and few openly gay individuals. These equilibria can be escaped via trigger events, that by causing even a small number of individuals to display their support for LGBT causes, can cause more individuals to come out, leading to more support, etc. We then evaluate our model with a large, online archival dataset on the timing of coming out decisions and public displays of support for LGBT causes for several million Americans. Using state-specific shocks to each, aggregate network data, and instrumental variables, we show how increases in LGBT support lead to elevated coming out rates in highly connected areas, and vice-versa. Chapter 2 studies a recent hypothesis that posits maternal vitamin D levels during pregnancy may affect the probability the fetus later develops asthma. Employing two large-scale studies, we test this hypothesis using a natural experiment afforded by historical variation in sunlight, a major source of vitamin D. Specifically, holding the birth location and month fixed, we see how exogenous within-location variation in sunlight across birth years affects the probability of asthma onset. We find highly significant evidence in both datasets that increased sunlight during the second trimester substantially lowers the subsequent probability of asthma. Finally, Chapter 3 is an evolutionary game theory paper about population structure. We provide a general, modularity-based framework for studying evolutionary games on structured populations under 'weak selection' that includes many previously known results as special cases. Our framework helps to show how these past disparate results are connected, and we exploit this insight to develop a general method for quantifying in closed form the effect of population structure on evolutionary dynamics. We illustrate our framework by proposing and solving a new model that generates a simple rule for the evolution of cooperation on endogenous dynamic networks.by Nils Christian Wernerfelt.Ph. D