Björn Wallace

Heritability of cooperative behavior in the trust game

Although laboratory experiments document cooperative behavior in humans, little is known about the extent to which individual differences in cooperativeness result from genetic and environmental variation. In this article, we report the results of two independently conceived and executed studies of monozygotic and dizygotic twins, one in Sweden and one in the United States. The results from these studies suggest that humans are endowed with genetic variation that influences the decision to invest, and to reciprocate investment, in the classic trust game. Based on these findings, we urge social scientists to take seriously the idea that differences in peer and parental socialization are not the only forces that influence variation in cooperative behavior.

No Association between Oxytocin Receptor (OXTR) Gene Polymorphisms and Experimentally Elicited Social Preferences

Background Oxytocin (OXT) has been implicated in a suite of complex social behaviors including observed choices in economic laboratory experiments. However, actual studies of associations between oxytocin receptor (OXTR) gene variants and experimentally elicited social preferences are rare. Methodology/Principal Findings We test hypotheses of associations between social preferences, as measured by behavior in two economic games, and 9 single nucleotide polymorphisms (SNPs) of the OXTR gene in a sample of Swedish twins (n = 684). Two standard economic games, the dictator game and the trust game, both involving real monetary consequences, were used to elicit such preferences. After correction for multiple hypothesis testing, we found no significant associations between any of the 9 single nucleotide polymorphisms (SNPs) and behavior in either of the games. Conclusion We were unable to replicate the most significant association reported in previous research between the amount donated in a dictator game and an OXTR genetic variant.

Heritability of Overconfidence

Empirical evidence suggests that people on average overestimate their own ability in a variety of circumstances. Little is known, however, about the origins of such overconfidence. To shed some light on this issue, we use the classic twin design to estimate the genetic and environmental contributions to individual differences in overconfidence. We collect data on overconfidence among 460 twin pairs. Overconfidence is measured as the difference between the perceived and actual rank in cognitive ability. Cognitive ability is measured using a 20-minute test of general intelligence. We find a highly significant joint effect of genes and common environment, but our estimates of the relative contributions of genetic and common environmental variation are less precise. According to our point estimates, genetic differences explain 16-34% of the variation in overconfidence depending on the definition of overconfidence used and common environmental differences explain 5-11%. (JEL: C91, D87, Z13) (c) 2009 by the European Economic Association.

Experimental game theory and behavior genetics.

We summarize the findings from a research program studying the heritability of behavior in a number of widely used economic games, including trust, dictator, and ultimatum games. Results from the standard behavior genetic variance decomposition suggest that strategies and fundamental economic preference parameters are moderately heritable, with estimates ranging from 18 to 42%. In addition, we also report new evidence on so‐called “hyperfair” preferences in the ultimatum game. We discuss the implications of our findings with special reference to current efforts that seek to understand the molecular genetic architecture of complex social behaviors.

Is there an adverse effect of sons on maternal longevity

Recent years have witnessed the emergence of a literature examining the effects of giving birth to sons on postmenopausal longevity in pre-industrial mothers. The original paper in this lineage used a sample (n=375) of Sami mothers from northern Finland and found that, relative to daughters, giving birth to sons substantially reduced maternal longevity. We examine this hypothesis using a similar and a much larger sample (n=930) of pre-industrial Sami women from northern Sweden, who in terms of their demographic, sociocultural and biological conditions, closely resemble the original study population. In contrast to the previously reported results for the Sami, we find no evidence of a negative effect of sons on maternal longevity. Thus, we provide the most compelling evidence to date that the leading result in the literature must be approached with scepticism.

Does parental age difference affect offspring count in humans? Comment on Fieder and Huber

In a recent paper, [Fieder & Huber (2007)][1] attempt to estimate the ‘fitness effects’ of parental age differences, to test the hypothesis that age preferences are evolutionarily acquired. The authors use modern data from the Swedish Total Population Registry . In their specifications, [Fieder

Maternal longevity and the sex of offspring in pre-industrial Sweden

Background: Helle et al. (2000. Sons reduced maternal longevity in preindustrial humans. Science, 296, 1085) argued that giving birth to sons reduced maternal longevity in pre-industrial societies due to higher physiological costs of bearing sons and the elevated testosterone levels observed in mothers carrying male foetuses. Aim: The present study examined this hypothesis using a more comprehensive dataset and evaluated the merits of the statistical approach used in previous studies to identify the cost of giving birth to sons in terms of maternal old-age longevity. Subjects and methods: The analysis in Helle et al. (2002. Sons reduced maternal longevity in preindustrial humans. Science 296, 1085) was extended by using a considerably larger dataset of pre-industrial Swedish women, and with careful consideration paid to methodological problems of sample selection and omitted variable bias. We argue that the previous literature has underestimated the difficulties in quantifying the trade-off between parity and longevity due to unobserved heterogeneity in health. However, under less restrictive assumptions, one can estimate the marginal impact of a son for a fixed family size. Results: No evidence was found of a negative relative impact of sons. Neither was any evidence found in favour of the male-biased intra-household resource competition hypothesis proposed elsewhere in the literature, despite the poverty of the study population. These results are robust to a wide range of specifications tested. Conclusion: The failure to reproduce earlier findings and the fact that studies in this area of research seem to continue to yield conflicting results warrant much caution in discussing and evaluating results. It is likely that the negative effect of sons, if it existed, only manifested itself under conditions that are not yet fully understood. We also argue that the previous literature on this topic has not fully acknowledged the inference problems associated with omitted variable bias and sample selection.

Fiscal Illusion and Fiscal Obfuscation: An Empirical Study of Tax Perception in Sweden

In this paper we present survey evidence suggesting that there exists a sizeable fiscal illusion amongst the general public in Sweden. Respondents in a nation-wide and representative survey systematically underestimate the share of an ordinary worker’s income that is transferred to the public sector. Furthermore, we make a theoretical distinction between tax illusion and fiscal obfuscation, a proposed novel type of fiscal illusion. It has previously been assumed that fiscal illusion derives from a fragmentized tax system with many small, and largely invisible, taxes which tend to be ignored or underestimated by the tax payers. We hypothesize that this systematic bias could in addition emanate from misapprehensions of the real incidence of a tax. Evidence is presented that this could apply even when taxes are few and large, contrary to the tax complexity hypothesis. When this misperception derives from seemingly deliberate tax design and tax labeling, as appears to be the case with the payroll taxes in Sweden, we call it fiscal obfuscation.

Reply to Helle et al.

We are grateful for the opportunity to respond to Helle, Lumma and Jokelas (henceforth HLJ; [Helle et al. 2010][1]) comment on our work. HLJ attribute to us the conclusion that the results in [Helle et al. (2002)][2] were ‘probably false positive owing to smaller sample size’. This is puzzling