抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Behavioral scientists routinely publish broad claims about human psychology and behavior in the world's top journals based on samples drawn entirely from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Researchers - often implicitly - assume that either there is little variation across human populations, or that these "standard subjects" are as representative of the species as any other population. Are these assumptions justified? Here, our review of the comparative database from across the behavioral sciences suggests both that there is substantial variability in experimental results across populations and that WEIRD subjects are particularly unusual compared with the rest of the species - frequent outliers. The domains reviewed include visual perception, fairness, cooperation, spatial reasoning, categorization and inferential induction, moral reasoning, reasoning styles, self-concepts and related motivations, and the heritability of IQ. The findings suggest that members of WEIRD societies, including young children, are among the least representative populations one could find for generalizing about humans. Many of these findings involve domains that are associated with fundamental aspects of psychology, motivation, and behavior - hence, there are no obvious a priori grounds for claiming that a particular behavioral phenomenon is universal based on sampling from a single subpopulation. Overall, these empirical patterns suggests that we need to be less cavalier in addressing questions of human nature on the basis of data drawn from this particularly thin, and rather unusual, slice of humanity. We close by proposing ways to structurally re-organize the behavioral sciences to best tackle these challenges.

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The WEIRDest People in the World

We demonstrate that a simple model, constructed on the premise that people are motivated by both their pecuniary payoff and their relative payoff standing, organizes a large and seemingly disparate set of laboratory observations as one consistent pattern The model is incomplete information but nevertheless posed entirely in terms of directly observable variables The model explains observations from games where equity is thought to be a factor, such as ultimatum and dictator, games where reciprocity is thought to play a role, such as the prisoner's dilemma and gift exchange, and games where competitive behavior is observed, such as Bertrand markets (JEL C78, C90, D63, D64, H41)

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ERC: A Theory of Equity, Reciprocity, and Competition

This paper discusses the discounted utility (DU) model: its historical development, underlying assumptions, and "anomalies" - the empirical regularities that are inconsistent with its theoretical predictions. We then summarize the alternate theoretical formulations that have been advanced to address these anomalies. We also review three decades of empirical research on intertemporal choice, and discuss reasons for the spectacular variation in implicit discount rates across studies. Throughout the paper, we stress the importance of distinguishing time preference, per se, from many other considerations that also influence intertemporal choices.

/pdf/time-discounting-and-time-preference-a-critical-review-47don96ek5.pdf

Time Discounting and Time Preference: A Critical Review

A menu of paired lottery choices is structured so that the crossover point to the high-risk lottery can be used to infer the degree of risk aversion With normal laboratory payoffs of several dollars, most subjects are risk averse and few are risk loving Scaling up all payoffs by factors of twenty, fifty, and ninety makes little difference when the high payoffs are hypothetical In contrast, subjects become sharply more risk averse when the high payoffs are actually paid in cash A hybrid "power/expo" utility function with increasing relative and decreasing absolute risk aversion nicely replicates the data patterns over this range of payoffs from several dollars to several hundred dollars

Risk Aversion and Incentive Effects

We design experiments to jointly elicit risk and time preferences for the adult Danish population. Since subjects are generally risk averse, we find that joint elicitation provides estimates of discount rates that are significantly lower than those found in previous studies and more in line with what would be considered as a priori reasonable rates. The statistical specification relies on a theoretical framework that involves a latent trade-off between long-run optimization and short-run temptation. Estimation of this specification is undertaken using structural, maximum likelihood methods. Our main results based on exponential discounting are robust to alternative specifications such as hyperbolic discounting. These results have direct implications for attempts to elicit time preferences, as well as debates over the appropriate domain of the utility function when characterizing risk aversion and time consistency.

/pdf/eliciting-risk-and-time-preferences-6emwxa1vh9.pdf

Eliciting risk and time preferences.

We estimate individual discount rates with respect to time streams of money using controlled laboratory experiments. These discount rates are elicited by means of field experiments involving real monetary rewards. The experiments were carried out across Denmark using a representative sample of 268 people between 19 and 75 years of age. Individual discount rates are estimated for various households differentiated by socio-demographic characteristics such as income and age. Our conclusions are that discount rates are constant over the 12-month to 3-year horizons used in these experiments, and that discount rates vary substantially with respect to several socio-demographic variables. Hence we conclude that it would be reasonable to assume constant discount rates for specific household types, but not the same rates across all households.

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Estimating Individual Discount Rates in Denmark: A Field Experiment

We review the experimental evidence on risk aversion in controlled laboratory settings. We review the strengths and weaknesses of alternative elicitation procedures, the strengths and weaknesses of alternative estimation procedures, and finally the effect of controlling for risk attitudes on inferences in experiments.

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Risk Aversion in the Laboratory

We examine the properties of a popular method for eliciting choices and values from experimental subjects, the multiple price list format. The main advantage of this format is that it is relatively transparent to subjects and provides simple incentives for truthful revelation. The main disadvantages are that it only elicits interval responses, and could be susceptible to framing effects. We consider extensions to address and evaluate these concerns. We conclude that although there are framing effects, they can be controlled for with a design that allows for them. We also find that the elicitation of risk attitudes is sensitive to procedures, subject pools, and the format of the multiple price list table, but that the qualitative findings that participants are generally risk averse is robust. The elicitation of discount rates appear less sensitive to details of the experimental design.

/pdf/elicitation-using-multiple-price-list-formats-56yryw2i42.pdf

Elicitation using multiple price list formats

The use of dichotomous choice (DC) methods has become increasingly common in applications of the contingent-valuation method (CVM)1 to elicit the "homegrown value" that an individual might have for nonmarket environmental goods.2 This hypothetical DC method involves a subject responding yes or no to a hypothetical question that asks whether or not he would be willing to make a commitment to pay some stated amount contingent upon the provision of an environmental good. The growing use of this method is primarily based on the assumption that the method yields incentive-compatible results. This implies that subjects will answer the CVM's hypothetical question in the same way as they would answer an identical question asking for a real economic commitment and that, therefore, the hypothetical DC method will result in accurate estimates of true willingness to pay. Explicit or implicit acceptance of this assumption is seen in a number of recent studies. For example, the use of the DC method in CVM studies is strongly recommended by a panel3 convened by the National Oceanic and Atmospheric Administration (NOAA) of the United States Department of Commerce to examine the use of hypothetical CVM survey questions (see NOAA, 1993 pp. 4608, 4608, 4612). The hypothetical DC method has been used by the Attorney General of the State of Alaska in a major application of the CVM to assess damages caused by the Exxon Valdez oil spill of 1989 (see Richard T. Carson et al., 1992). A major CVM study of potential environmental damages due to proposed mining activity in the Kakadu Conservation Zone of Australia employed the DC method with a similar rationale (see David Imber et al., 1991 p. vi). It is clear that if a subject perceives that his expected utility is affected by the possibility of the good actually being provided he has no incentive to misrepresent. We can presume that in an application of a real DC method, where payment and provision of * Cummings: Policy Research Center, College of Business Administration, Georgia State University, Atlanta, GA 30303-3083; Harrison and Rutstr6m: Department of Economics, College of Business Administration, University of South Carolina, Columbia, SC 29208. We are grateful to Peter Bohm, Bengt Kristr6m, and three referees for helpful comments. Ashley Abbott, Lloyd Brown, Colin Day, Tanga McDaniel, Helen Neill, and Melonie Williams provided excellent research assistance. We acknowledge financial support provided by the State of New Mexico's Waste Management Education and Research Consortium and Resources for the Future. We retain responsibility for all errors. 'For a critical review of the debate over the CVM, see Cummings and Harrison (1994) 2"Homegrown value" is a term primarily used in experimental economics. It refers to a subject's value that is independent of the value which an experimenter might "induce" for the good (see Vernon L. Smith, 1976). The idea is that homegrown values are those that the subject brings to an experiment. 3Consisting of Kenneth Arrow (Co-chair), Robert Solow (Co-chair), Paul R. Portney, Edward E. Leamer, Roy Radner, and Howard Schuman.

Glenn W. Harrison

Papers

Eliciting risk and time preferences.

Estimating Individual Discount Rates in Denmark: A Field Experiment

Risk Aversion in the Laboratory

Elicitation using multiple price list formats

Homegrown Values and Hypothetical Surveys: Is the Dichotomous Choice Approach Incentive-Compatible?