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

Introduction 1. Woman's Place in Man's Life Cycle 2. Images of Relationship 3. Concepts of Self and Morality 4. Crisis and Transition 5. Women's Rights and Women's Judgment 6. Visions of Maturity References Index of Study Participants General Index

In a Different Voice. Psychological Theory and Women’s Development. Cambridge, MA (Harvard University Press) 1982.

Virtually all current theories of choice under risk or uncertainty are cognitive and consequentialist. They assume that people assess the desirability and likelihood of possible outcomes of choice alternatives and integrate this information through some type of expectation-based calculus to arrive at decision. The authors propose an alternative theoretical perspective, the risk-as-feelings hypothesis, that highlights the role of affect experienced at the moment of decision making. Drawing on research from clinical, physiological, and other subfield of psychology, they show that emotional reactions to risky situations often drive behavior. The risk-as-feelings hypothesis is shown to explain a wide range of phenomena that have resisted interpretation in cognitive-consequentialist terms.

Risk as Feelings

This paper reviews the literature on gender differences in economic experiments. In the three main sections, we identify robust differences in risk preferences, social (other-regarding) preferences, and competitive preferences. We also speculate on the source of these differences, as well as on their implications. Our hope is that this article will serve as a resource for those seeking to understand gender differences and to use as a starting point to illuminate the debate on gender-specific outcomes in the labor and goods markets.

/pdf/gender-differences-in-preferences-1wffy691ko.pdf

Gender Differences in Preferences

Virtually all current theories of choice under risk or uncertainty are cognitive and consequentialist. They assume that people assess the desirability and likelihood of possible outcomes of choice alternatives and integrate this information through some type of expectation-based calculus to arrive at a decision. The authors propose an alternative theoretical perspective, the risk-as-feelings hypothesis, that highlights the role of affect experienced at the moment of decision making. Drawing on research from clinical, physiological, and other subfields of psychology, they show that emotional reactions to risky situations often diverge from cognitive assessments of those risks. When such divergence occurs, emotional reactions often drive behavior. The risk-as-feelings hypothesis is shown to explain a wide range of phenomena that have resisted interpretation in cognitive-consequentialist terms.

Risk as feelings.

Economics seems largely based on the assumption that monetary incentives improve performance. By contrast, a large literature in psychology, including a rich tradition of experimental work, claims just the opposite. In this paper we present and discuss a set of experiments designed to test the effect of different monetary compensations on performance. In our experiments we find that whenever money is offered, a larger amount yields a higher performance. It is not true, however, that offering money always induces a higher performance: participants who were offered a small payoff gave a worse performance than those who were offered no compensation at all. These results suggest that the behavior of participants is influenced by their perception of the contract that is offered to them. When the contract offers money the environment is perceived as monetary, and participants respond in a qualitatively different way in monetary and non-monetary environments. In a different set of experiments we test subjects who, acting as principals, have to provide the appropriate incentive to agents. We show that principals do not anticipate the drastic difference in behavior. The vast majority of principals seem to think incorrectly that a larger compensation is unambiguously a better incentive.

Pay Enough or Don't Pay at All

Even though the provision of equal opportunities for men and women has been a priority in many countries, large gender differences prevail in competitive high-ranking positions. Suggested explanations include discrimination and differences in preferences and human capital. In this paper we present experimental evidence in support of an additional factor: women may be less effective than men in competitive environments, even if they are able to perform similarly in non-competitive environments. In a laboratory experiment we observe, as we increase the competitiveness of the environment, a significant increase in performance for men, but not for women. This results in a significant gender gap in performance in tournaments, while there is no gap when participants are paid according to piece rate. This effect is stronger when women have to compete against men than in single-sex competitive environments: this suggests that women may be able to perform in competitive environments per se.

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Performance in Competitive Environments: Gender Differences

The deterrence hypothesis predicts that the introduction of a penalty that leaves everything else unchanged will reduce the occurrence of the behavior subject to the fine. We present the result of a field study in a group of day‐care centers that contradicts this prediction. Parents used to arrive late to collect their children, forcing a teacher to stay after closing time. We introduced a monetary fine for late‐coming parents. As a result, the number of late‐coming parents increased significantly. After the fine was removed no reduction occurred. We argue that penalties are usually introduced into an incomplete contract, social or private. They may change the information that agents have, and therefore the effect on behavior may be opposite of that expected. If this is true, the deterrence hypothesis loses its predictive strength, since the clause “everything else is left unchanged” might be hard to satisfy.

A fine is a price

Deception is part of many economic interactions. Business people, politicians, diplomats, lawyers, and students in the experimental laboratory who make use of private information do not always do so honestly. This observation indicates that behavior often rejects the moral approach to deception. As St. Augustine wrote, “To me, however, it seems certain that every lie is a sin. . . ” (St. Augustine, 421). Later, philosophers like Immanuel Kant (1787) again adopted this uncompromising moral stance when arguing against lying. At the other extreme, economic theory is built on the assumption of “homo economicus,” a figure who acts selfishly and is unconcerned about the well-being of others. An implication of this assumption is that lies will be told whenever it is beneficial for the liar, regardless of their effect on the other party. Another implication is that there is no negative outcome associated with lying per se. This assumption is very useful in many economic models. Consider contract theory, where it is assumed that without an explicit contract, neither side will fulfill its respective obligations. For example, George Akerlof’s (1970) paper on asymmetric information and the market for lemons assumes that sellers of used cars will always lie if it is in their benefit to do so. In the mechanism design literature (e.g., Bengt Holmstrom, 1979), the standard assumption is that people will tell the truth only if this is incentive-compatible given material outcomes. In the literature on tax evasion, the choice of whether to avoid paying taxes is considered a decision under uncertainty; cost is treated as a product of the probability of being caught and the cost of punishment, whereas benefit is simply the money saved by avoiding payment. However, there is no cost associated with the very act of lying (Michael Alingham and Agnar Sandmo, 1972). Another example is the game theoretic treatment of “cheap talk” (Crawford and Joel Sobel, 1982). An intermediate approach is taken by utilitarian philosophers (e.g., Jeremy Bentham, 1789). Utilitarianism prescribes that, when choosing whether to lie, one should weigh benefits against harm, and happiness against unhappiness. As Martin Luther stated, “What harm would it do, if a man told a good strong lie for the sake of the good and for the Christian church. . . a lie out of necessity, a useful lie, a helpful lie, such lies would not be against God, he would accept them.” Similarly to the economic theory approach, this type of calculation implies that lies, apart from their resultant harm and benefit, are in themselves neutral. A lie and a truthful statement that achieve the same monetary payoffs (for both sides) are considered * Graduate School of Business, University of Chicago, 5807 South Woodlawn Avenue, Chicago, IL 60637 (e-mail: uri.gneezy.gsb.uchicago.edu). I thank Douglas Bernheim and two anonymous reviewers for insightful comments that considerably improved the paper. I also thank Andreas Blume, Gary Charness, Rachel Croson, Martin Dufwenberg, Georg Kirchsteiger, David Levine, Muriel Niederle, Yuval Rottenstreich, Maurice Schweitzer, Richard Thaler, George Wu, and seminar participants at numerous universities for their comments and suggestions. Ira Leybman provided valuable help in running the experiment. I became interested in deception when my father was terminally ill and his physicians created in him a belief that they considered to be untrue. I dedicate this paper to his memory. 1 Important deviations from this assumption in economic modeling are found in Kenneth Arrow’s (1972) discussion of trust, Gary Becker’s (1976) modeling of altruistic preferences, and Akerlof’s (1982) study of the fair-wage hypothesis. For a general discussion, see Becker (1993): “The economic approach I refer to does not assume that individuals are motivated solely by selfishness or material gain. It is a method of analysis, not an assumption about particular motivations. Along with others, I have tried to pry economists away from narrow assumptions about self-interest. Behavior is driven by a much richer set of values and preferences” (p. 385). 2 Note that this does not mean that a completely selfish person will always lie. There may be strategic reasons not to lie. For example, see the David Kreps and Robert Wilson (1982) discussion of reputation and imperfect information; see also Vincent P. Crawford (2003). 3 Cited by his secretary, in a letter in Max Lenz, ed., Briefwechsel Landgraf Phillips des Grossmuthigen von Hessen mit Bucer, Vol. 1.

Uri Gneezy

Papers

Gender Differences in Preferences

Pay Enough or Don't Pay at All

Performance in Competitive Environments: Gender Differences

A fine is a price

Deception: The Role of Consequences