Social consistency and individual rationality

This paper aims at proving that social interactions can easily be rationalized by individual preferences as defined in standard microeconomic theory. For that purpose, we show individual choice rationality to be logically equivalent to social consistency, when individual rationality means that individual preferences are completely ordered and social consistency that there is a one-to-one mapping between a given family of social communities and the existence of a particular (unique, reflexive and symmetric) interaction relation between individuals. Moreover, continuity and monotonicity of individual preferences are shown to fit the modeling of group loyalty when group loyalty is defined as the ability to freely accept a personal loss for the global gain of a particular population.preferences ; social interaction ; communities ; group loyalty

How to shake the Invisible Hand (when Robinson meets Friday)

We propose to define the invisible hand by (i) modelling the mechanism itself (not to just assume its existence) and (ii) making explicit the limit conditions for its working. For that purpose, we simply assimilate the working of the invisible hand mechanism to the existence of a social preference such that individual and social optimalities are consistent. In introducing the possibility of interaction among individuals, we then suggest that the standard Robinson case or social atomicity is just a degenerate feature of a more general requirement that we call the Global Network Agreement. Our main result is that the invisible hand mechanism does keep on working when there is an interaction between Robinson and Friday if the former (resp. the latter) is sensitive to the latter (resp. the former) in such a way that they exhibit some agreement in preferences. Hence, the Robinson case naturally satisfies this property since nor Robinson neither Friday can disagree with himself. But more cooperative situations are also allowed in order to extent the invisible hand mechanism to cases with interactions.preferences ; social interaction ; invisible hand

How to shake the Invisible Hand (when Robinson meets Friday)

We propose to define the invisible hand by (i) modelling the mechanism itself (not to just assume its existence) and (ii) making explicit the limit conditions for its working. For that purpose, we simply assimilate the working of the invisible hand mechanism to the existence of a social preference such that individual and social optimalities are consistent. In introducing the possibility of interaction among individuals, we then suggest that the standard Robinson case or social atomicity is just a degenerate feature of a more general requirement that we call the Global Network Agreement. Our main result is that the invisible hand mechanism does keep on working when there is an interaction between Robinson and Friday if the former (resp. the latter) is sensitive to the latter (resp. the former) in such a way that they exhibit some agreement in preferences. Hence, the Robinson case naturally satisfies this property since nor Robinson neither Friday can disagree with himself. But more cooperative situations are also allowed in order to extent the invisible hand mechanism to cases with interactions.Nous proposons de définir la main invisible sous la forme d'un mécanisme formel explicite. Pour cela, nous assimilons ce mécanisme à l'existence d'une relation de préférence sociale telle que les optimalités individuelle et collective soient compatibles. Puis en introduisant une possibilité d'interaction entre agents, nous suggérons que le cas standard (Adam Smith) d'atomicité sociale constitue le cas limite d'une classe plus générale de situations satisfaisant toutes une certaine contrainte appelée le Global Network Agreement (ou Accord Global de Réseau). Notre résultat principal est alors que le mécanisme de la main invisible s'applique même en présence d'interactions dès lors que les agents qui interagissent sont sensibles en préférence les uns aux autres d'une manière telle qu'ils manifestent entre eux un consensus minimal. Aussi, le cas standard (chaque agent est un Robinson) satisfait naturellement cette propriété, cependant, d'autres cas, beaucoup plus coopératifs sont eux aussi aussi compatibles avec le mécanisme de la main invisible

Social consistency and individual rationality

This paper aims at proving that social interactions can easily be rationalized by individual preferences as defined in standard microeconomic theory. For that purpose, we show individual choice rationality to be logically equivalent to social consistency, when individual rationality means that individual preferences are completely ordered and social consistency that there is a one-to-one mapping between a given family of social communities and the existence of a particular (unique, reflexive and symmetric) interaction relation between individuals. Moreover, continuity and monotonicity of individual preferences are shown to fit the modeling of group loyalty when group loyalty is defined as the ability to freely accept a personal loss for the global gain of a particular population.Cet article vise à montrer que les interactions sociales peuvent être déduites des relations individuelles de préférence (et vice versa). Nous montrons ainsi que le postulat de rationalité individuelle est logiquement équivalent à celui de cohérence sociale dès lors que le postulat de rationalité individuelle signifie que les préférences des agents sont des préordres complets et celui de cohérence sociale, qu'il existe une bijection entre chaque système de coalitions et la relation d'interaction (unique, réflexive et symétrique) qui le soutend. De plus, on montre que la continuité et la monotonie des préférences individuelles permettent de modéliser la notion de loyauté communautaire dès lors que la loyauté communautaire est définie en tant que la capacité des agents à accepter une perte personnelle d'utilité au profit d'un gain collectif pour une coalition particulière

Axiomatization of an Exponential Similarity Function

An agent is asked to assess a real-valued variable y based on certain characteristics x=(x^{1},...,x^{m}), and on a database consisting of n observations of (x^{1},...,x^{m},y). A possible approach to combine past observations of x and y with the current values of x to generate an assessment of y is similarity-weighted averaging. It suggests that the predicted value of y, y_{n+1}^{s}, be the weighted average of all previously observed values y_{i}, where the weight of y_{i} is the similarity between the vector x_{n+1}^{1},...,x_{n+1}^{m}, associated with y_{n+1}, and the previously observed vector, x_{i}^{1},...,x_{i}^{m}. This paper axiomatizes, in terms of the prediction y_{n+1}, a similarity function that is a (decreasing) exponential in a norm of the difference between the two vectors compared.Similarity, exponential

Learning by Helping: A Bounded Rationality Model of Mentoring

Within an organization, a bounded rational principal organizes a promotion test based on a sequence of test regarding candidates' relative performances. We assume the principal to suffer from limited ability to rank the performances, only identifying the best in each test. Furthermore, he satisfies the expected gains do not decreases whit the information generated by additional tests. Then, mentoring is shown to improve the information about candidates' ability when the principal offers help to the current best candidate provided by a manager promoted after a similar contest.Mentoring; Selection; Contests; Bounded Rationality

Multiplayer belief revision

One main topic of the epistemic program of game theory deals with the value of information. To study this question in a broad context, one needs to adapt some of the tools used in multiplayer epistemic logic. A hierarchical belief structure is introduced both in a syntactical and semantical framework. In the same framework, a generalized notion of message is characterized by its content and its status. For a given message, a multiplayer belief revision rule that transforms any initial belief structure into a final belief one is designed. A representation theorem relates syntactical axioms to the belief revision rule.Belief revision, message, epistemic logic.

Expected Utility without Parsimony

URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/cesdp2014.htmlDocuments de travail du Centre d'Economie de la Sorbonne 2014.48 - ISSN : 1955-611XThis paper seeks to interpret observable behavior and departures from Savage's model of Subjective Expected Utility (SEU) in terms of knowledge and belief. It is shown that observable behavior displays sensitivity to ambiguity if and only if knowledge and belief disagree. In addition, such an epistemic interpretation of ambiguity leads to dynamically consistent extensions of non-SEU preferences.Ce papier cherche à interpréter le comportement observable d'un individu, et notamment les violations du modèle d'espérance subjective d'utilité (SEU), en termes de savoir et de croyance. Il est montré que le comportement observable révèle de la sensitivité à l'ambiguïté si et seulement si savoir et croyance diffèrent. De plus, une telle interprétation épistémique de l'ambiguïté mène à des extensions dynamiquement cohérentes des préférences non-SEU

Utilitarianism with Prior Heterogeneity

URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/cesdp2014.htmlDocuments de travail du Centre d'Economie de la Sorbonne 2014.49 - ISSN : 1955-611XHarsanyi's axiomatic justification of utilitarianism is extended to a framework with subjective and heterogenous priors. Contrary to the existing literature on aggregation of preferences under uncertainty, society is here allowed to formulate probability judgements, not on the actual state of the world as individuals do, but rather on the opinion they each have on the actual state. An extended Pareto condition is then proposed that characterizes the social utility function as a convex combination of individual ones and the social prior as the independent product of individual ones.La justification axiomatique de l'utilitarisme d'Harsanyi est généralisée à un cadre dans lequel les croyances individuelles sont subjectives et hétérogènes. A l'inverse de la littérature existante sur l'agrégation de préférences en environnement incertain, la société formule des jugements de probabilité, non pas sur le véritable état du monde - ce que les individus font -, mais plutôt sur les opinions qu'entretiennent les individus à propos du véritable état du monde. Une forme étendue de la condition de Pareto est alors proposée et il est montré qu'elle caractérise l'utilité sociale en tant que combinaison convexe des utilités individuelles et la probabilité sociale en tant que produit indépendant des probabilités individuelles