Expert Information and Majority Decisions

This paper studies dichotomous majority voting in common interest committees where each member receives not only a private signal but also a public signal observed by all of them. The public signal represents, e.g. expert information presented to an entire committee and its quality is higher than that of each individual private signal. We identify two informative symmetric strategy equilibria, namely i) the mixed strategy equilibrium where each member randomizes between following the private and public signals should they disagree; and ii) the pure strategy equilibrium where they follow the public signal for certain. The former outperforms the latter. The presence of the public signal precludes the equilibrium where every member follows their own signal, which is an equilibrium in the absence of the public signal. The mixed strategy equilibrium in the presence of the public signal outperforms the sincere voting equilibrium without the public signal, but the latter may be more efficient than the pure strategy equilibrium in the presence of the public signal. We suggest that whether expert information improves committee decision making depends on equilibrium selection.

Trypanosoma nupelianus sp. n. (Protozoa, Kinetoplastida) parasitizing rhinelepis aspera (Osteichthyes, Loricariidae) from Paraná river, Brazil

It is described Trypanosoma nupelianus sp. n. parasitizing Rhinelepis aspera taken from Paraná river (Itaipu reservoir, Brazil). Morphometric characters such as body length, width of the body and nucleus dimensions show that T. nupelianus sp. n. is different from other trypanosomes described for fishes from tropical regions.

Confidence and Competence in Communication

This paper studies information transmission between an uninformed decision maker (receiver) and an informed player (sender) who have asymmetric beliefs ("con fidence") on the sender s ability ("competence") to observe the state of nature. We fi nd that even when the material payoffs of are perfectly aligned, the sender s over- and underconfi dence on his information give rise to information loss in communication, although they do not by themselves completely eliminate information transmission in equilibrium. However, an underconfi dent sender may prefer no communication to informative communication. We also show that when the sender is biased, overconfi dence can lead to more information transmission and welfare improvement.

Efficient Competition through Cheap Talk: Competing Auctions and Competitive Search without Ex Ante Price

We consider a frictional two-sided matching market in which one side uses public cheap talk announcements so as to attract the other side. We show that if the first-price auction is adopted as the trading protocol, then cheap talk can be perfectly informative, and the resulting market outcome is efficient, constrained only by search frictions. We also show that the performance of an alternative trading protocol in the cheap-talk environment depends on the level of price dispersion generated by the protocol: If a trading protocol compresses (spreads) the distribution of prices relative to the first-price auction, then an efficient fully revealing equilibrium always (never) exists. Our results identify the settings in which cheap talk can serve as an efficient competitive instrument, in the sense that the central insights from the literature on competing auctions and competitive search continue to hold unaltered even without ex ante price commitment.

Coordination in Public Good Provision: How Individual Volunteering is Impacted by the Volunteering of Others

In this analysis, we examine the relationship between an individual's decision to volunteer and the average level of volunteering in the community where the individual resides. Our theoretical model is based on a coordination game , in which volunteering by others is informative regarding the benefit from volunteering. We demonstrate that the interaction between this information and one's private information makes it more likely that he or she will volunteer, given a higher level of contributions by his or her peers. We complement this theoretical work with an empirical analysis using Census 2000 Summary File 3 and Current Population Survey (CPS) 2004-2007 September supplement file data. We control for various individual and community characteristics, and employ robustness checks to verify the results of the baseline analysis. We additionally use an innovative instrumental variables strategy to account for reflection bias and endogeneity caused by selective sorting by individuals into neighborhoods, which allows us to argue for a causal interpretation. The empirical results in the baseline, as well as all robustness analyses, verify the main result of our theoretical model, and we employ a more general structure to further strengthen our results.

What is the Causal Effect of Information and Learning about a Public Good on Willingness to Pay?

In this study we elicit agents’ prior information set regarding a public good, exogenously give information treatments to survey respondents and subsequently elicit willingness to pay for the good and posterior information sets. The design of this field experiment allows us to perform theoretically motivated hypothesis testing between different updating rules: non-informative updating, Bayesian updating, and incomplete updating. We find causal evidence that agents imperfectly update their information sets. We also field causal evidence that the amount of additional information provided to subjects relative to their pre-existing information levels can affect stated WTP in ways consistent overload from too much learning. This result raises important (though familiar) issues for the use of stated preference methods in policy analysis.

Coordination in Public Good Provision: How Individual Volunteering is Impacted by the Volunteering of Others

In this analysis, we examine the relationship between an individual’s decision to volunteer and the average level of volunteering in the community where the individual resides. Our theoretical model is based on a coordination game , in which volunteering by others is informative regarding the benefit from volunteering. We demonstrate that the interaction between this information and one’s private information makes it more likely that he or she will volunteer, given a higher level of contributions by his or her peers. We complement this theoretical work with an empirical analysis using Census 2000 Summary File 3 and Current Population Survey (CPS) 2004-2007 September supplement file data. We control for various individual and community characteristics, and employ robustness checks to verify the results of the baseline analysis. We additionally use an innovative instrumental variables strategy to account for reflection bias and endogeneity caused by selective sorting by individuals into neighbourhoods, which allows us to argue for a causal interpretation. The empirical results in the baseline, as well as all robustness analyses, verify the main result of our theoretical model, and we employ a more general structure to further strengthen our results.

New insights into the phylogenetics and biogeography of Arum (Araceae): unravelling its evolutionary history

The heat- and odour-producing genus Arum (Araceae) has interested scientists for centuries. This long-term interest has allowed a deep knowledge of some complex processes, such as the physiology and dynamics of its characteristic lure-and-trap pollination system, to be built up. However, mainly because of its large distributional range and high degree of morphological variation, species' limits and relationships are still under discussion. Today, the genus comprises 28 species subdivided into two subgenera, two sections and six subsections. In this study, the phylogeny of the genus is inferred on the basis of four plastid regions, and the evolution of several morphological characters is investigated. Our phylogenetic hypothesis is not in agreement with the current infrageneric classification of the genus and challenges the monophyly of several species. This demonstrates the need for a new infrageneric classification based on characters reflecting the evolution of this enigmatic genus. To investigate the biogeography of Arum deeply, further spatiotemporal analyses were performed, addressing the importance of the Mediterranean basin in the diversification of Arum. Our results suggest that its centre of origin was the European-Aegean region, and that major diversification happened during the last 10 Myr.

Temper and Temperature: The Missing Link of Climate on Armed Conflicts

We investigate the causes of a conflict by adding ambient climate factors to the existing bundle of most significant variables. It turns out that – controlling for possible associations – temperature could actually induce a conflict. We emphasise that temperature could not be a dominant reason in starting a conflict; however, it could escalate the chances when other factors are present. This paper references some of the related psychological studies to support this claim. We also show that grievance factors could actually be rightfully effective in starting an internal conflict alongside greed based reasons. In the end, we believe that it could be informative to study ambient factors more often in economics.

Government information transparency

This paper studies a model of announcements by a privately informed government about the future state of the economic activity in an economy subject to recurrent shocks and with distortions due to income taxation. Although transparent communication would ex ante be desirable, we find that even a benevolent government may ex-post be non-informative, in an attempt to countervail the tax distortion with a "second best" compensating distortion in information. This result provides a rationale for independent national statistical offices, committed to truthful communication. We also find that whether inequality in income distribution favors or harms government transparency depends on labor supply elasticity.

Gastromermis cordobensis n. sp. (Nematoda: Mermithidae) parasitizing Simulium lahillei Patterson & Shannon (Diptera: Simuliidae) in Argentina

Gastromermis cordobensis n. sp (Nematoda: Mermithidae) a parasite of larvae of the blackfly Simulium lahillei Paterson & Shannon (Diptera: Simuliidae) in Argentina, is described. Diagnostic characters of this species include a mouth ventrlly shifted; six cephalic papillae; eigh hypodermal chords; small and pear shaped amphids; a long and S-shaped vagina; a singl spicule, which is long, has non-uniform walls, and a tip with sculpture; three rows of genital papillae, the middle one with 18 pre-anal and 10 post-anal papillae, the lateral rows have 36 papillae each; oval eggs; and post-parasitic juveniles with long thin tails. Pre-parasitic and parasitic juveniles are included in the description.

Biomphalaria prona (Gastropoda: Planorbidae): a morphological and biochemical study

Two samples of Biomphalaria prona (Martens, 1873) from Lake Valencia (type locality) and seven from other Venezuelan localities were studied morphologically (shell and reproductive system) and biochemically (allozyme electrophoresis). In spite of marked differences in shell characters, all of them proved indistinguishable under the anatomic and biochemical criteria. So far B. prona has been considered an endemic species, restricted to Lake Valencia. It is now demonstrated that the extralacustrine populations refered to Biomphalaria havanensis (Pfeiffer, 1839) by several authors correspond in shell characters to an extreme variant of B. prona from the Lake and really belong to the last*mentioned species. They may be regarded as the result of a process of directional selection favoring a shell phenotype other than those making up the modal class in the Lake.

Cytogenetics as a tool for Triatomine species distinction (Hemiptera-Reduviidae)

Several cytogenetic traits were tested a species diagnostic characters on five triatomine species: Rhodnius pictipes, R. nasutus, R. robustus, Triatoma matogrossensis and T. pseudomaculata. Four of them are described for the first time. The detailed analysis of the meiotic process and the application of C-banding allowed us to identify seven cytogenetic characters wich result useful to characterize and differentiate triatomine species.

El Giravolt de la Família Robafaves

Treball de recerca realitzat per un alumne d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit cientí­fic del Jovent l'any 2009. 'El Giravolt de la Família Robafaves' és un treball de recerca que engloba tota la història del fet geganter a Mataró des dels seus orígens fins a l'actualitat. Es tracta d'una activitat amb una dimensió cultural, folklòrica i històrica que ha servit per donar respostes a molts dels interrogants promulgats abans de dur a terme aquest projecte. Aquesta família de Gegants ha estat víctima de molts dels entrebancs vigents al llarg de la història així com guerres, revoltes, dictadures, etc. De manera que s'ha pogut comprovar com la política interior i exterior ha afectat a la Família Robafaves d'una manera directa. S'ha fet una investigació a través de les revistes publicades durant la transició democràtica. També cal dir que, s'ha tingut el recolzament d'entrevistes fetes a persones puntals en la història dels Gegants com ara geganters, Caps de Colla, la primera gegantera de la Família Robafaves, etc. Per poder corroborar la base teòrica i documental d'aquest treball s'ha fet un estudi estadístic de la significació social de la Festa Major de Mataró per poder valorar en quina situació es troba actualment. Així doncs, s'ha pogut valorar la influència i importància que tenen els Gegants per Mataró.

Gains from switching and evolutionary stability in multi-player matrix games.

In this paper we unify, simplify, and extend previous work on the evolutionary dynamics of symmetric N-player matrix games with two pure strategies. In such games, gains from switching strategies depend, in general, on how many other individuals in the group play a given strategy. As a consequence, the gain function determining the gradient of selection can be a polynomial of degree N-1. In order to deal with the intricacy of the resulting evolutionary dynamics, we make use of the theory of polynomials in Bernstein form. This theory implies a tight link between the sign pattern of the gains from switching on the one hand and the number and stability of the rest points of the replicator dynamics on the other hand. While this relationship is a general one, it is most informative if gains from switching have at most two sign changes, as is the case for most multi-player matrix games considered in the literature. We demonstrate that previous results for public goods games are easily recovered and extended using this observation. Further examples illustrate how focusing on the sign pattern of the gains from switching obviates the need for a more involved analysis.