Replication, Communication, and the Population Dynamics of Scientific Discovery

Many published research results are false, and controversy continues over the roles of replication and publication policy in improving the reliability of research. Addressing these problems is frustrated by the lack of a formal framework that jointly represents hypothesis formation, replication, publication bias, and variation in research quality. We develop a mathematical model of scientific discovery that combines all of these elements. This model provides both a dynamic model of research as well as a formal framework for reasoning about the normative structure of science. We show that replication may serve as a ratchet that gradually separates true hypotheses from false, but the same factors that make initial findings unreliable also make replications unreliable. The most important factors in improving the reliability of research are the rate of false positives and the base rate of true hypotheses, and we offer suggestions for addressing each. Our results also bring clarity to verbal debates about the communication of research. Surprisingly, publication bias is not always an obstacle, but instead may have positive impacts---suppression of negative novel findings is often beneficial. We also find that communication of negative replications may aid true discovery even when attempts to replicate have diminished power. The model speaks constructively to ongoing debates about the design and conduct of science, focusing analysis and discussion on precise, internally consistent models, as well as highlighting the importance of population dynamics

New methods in quantitative ethnography: economic experiments and variation in the price of equality

Journal ArticleA new method for quantitatively documenting concerns for economic fairness has the potential for identifying variation in prosociality within and across societies. Multiple dictator games conducted in two small-scale societies presented decision makers with a choice between an equitable and an inequitable payoff distribution. The games varied in terms of the type of inequality the decision maker faced and the cost to the decision maker of eliminating inequality. A novel set of statistical models directly links experimental results and player heterogeneity with the formal theory of inequality aversion. The experimental method can be generalized to allow maximum flexibility in data analysis

Are peasants risk-averse decision makers?

Journal ArticleFor decades, researchers studying small-scale, subsistence-oriented farmers have sought to explain why these "peasants" seem slow to acquire new technologies, novel agricultural practices, and new ideas from the larger societies that have engulfed them. The early work on this question suggested that this "cultural conservatism" resulted from things like a rigid adherence to tradition or custom, a cognitive orientation toward a "limited good," or ignorance and lack of education. In response to such explanations, much of the subsequent debate on this issue has focused on showing that this seeming conservatism actually results from rational cost benefit analysis in which individuals make risk-averse decisions because of their uncertain and precarious economic situations. To inform this approach, we have combined comparative experimental field studies with economically oriented ethnography among two groups of small-scale farmers, the Mapuche of Chile and the Sangu of Tanzania. Our experiments, which were designed to measure risk preferences directly, indicate that both the Mapuche and Sangu are risk-preferring (not risk-averse) decision makers in the standard economic sense--suggesting that subsistence farmers more generally may not be risk-averse either. Furthermore, while sex, age, land holdings, and income do not predict risk preferences and wealth is "at most" only marginally predictive, what does seem to predict risk preferences in our monetary gambles "cultural group." Although such experimental findings carry important caveats, they suggest that standard views of risk-averse decision making may not be the best theoretical tools for understanding "peasant conservatism" or the behavioral patterns often attributed to "rational risk aversion

In search of homo economicus: behavioral experiments in 15 small scale societies

Journal ArticleRecent investigations have uncovered large, consistent deviations from the predictions of the textbook representation of Homo economicus One problem appears to lie in economists' canonical assumption that individuals are entirely self-interested: in addition to their own material payoffs, many experimental subjects appear to care about fairness and reciprocity, are willing to change the distribution of material outcomes at personal cost, and are willing to reward those who act in a cooperative manner while punishing those who do not even when these actions are costly to the individual. These deviations from what we will term the canonical model have important consequences for a wide range of economic phenomena, including the optimal design of institutions and contracts, the allocation of property rights, the conditions for successful collective action, the analysis of incomplete contracts, and the persistence of noncompetitive wage premia

Shared norms and the evolution of ethnic markers

Journal ArticleUnlike other primates, human populations are often divided into ethnic groups that have self-ascribed membership and are marked by seemingly arbitrary traits such as distinctive styles of dress or speech (Barth 1969, 1981). The modern understanding that ethnic identities are flexible and ethnic boundaries porous makes the origin and existence of such groups problematic because the movement of people and ideas between groups will tend to attenuate group differences. Thus, the persistence of existing boundaries and the birth of new ones suggests that there must be social processes that resist the homogenizing effects of migration and the strategic adoption of ethnic identities

When natural selection favors imitation of parents

Journal ArticleIt is commonly assumed that parents are important sources of socially learned behavior and beliefs. However, the empirical evidence that parents are cultural models is ambiguous, and debates continue over their importance. A formal theory that examines the evolution of psychological tendencies to imitate parents (vertical transmission) and to imitate nonparent adults (oblique transmission) in stochastic fluctuating environments points to forces that sometimes make vertical transmission adaptive, but oblique transmission recovers more quickly from rapid environmental change