Gender Differences in Competition Emerge Early in Life

We study gender differences in the willingness to compete in a large-scale experiment with 1,035 children and teenagers, aged three to eighteen years. Using an easy math task for children older than eight years and a running task for the younger ones we find that boys are much more likely to enter a tournament than girls across the whole age spectrum considered here. This gender gap is observed already with three-year olds, indicating that gender differences in competitiveness emerge very early in life. The gap is robust to controlling for gender differences in risk attitudes and overconfidence.competition, gender gap, experiment, children, teenagers

Impact of Crustose Clionid Sponges on Caribbean Reef Corals

Some species of limestone-excavating Porifera (Clionidae, Hadromerida) cover their substrate as a thin, continuous, veneer-like crust (beta stage). This film of tissue is the result of fusion of the initially discrete incurrent and excurrent papillae (alpha stage) that are the common and lifelong morphological feature of most other representatives of the family. In the tropical and subtropical western Atlantic, at least four species of clionids encrust reef-coral skeletons (Scleractinia, Hydrozoa): Cliona caribbaea CARTER (including C. aprica PANG and C. langae PANG), C. delitrix PANG, C. lampa de LAUBENFELS, and C. varians (DUCHASSAING and MICH-ELOTTI) (=Anthosigmella varians of authors). One conspicuous feature of these encrusting sponges is that many border live coral or cover recently dead coral as indicated by the clear outline of the coral calicular structure under the thin sponge veneer. Field experiments and histological study conducted on Cliona caribbaea in Belize and Cliona lampa in Bermuda indicate that the sponges overpower stressed coral which they overgrow at a fast rate. Stress parameters include extended periods of above-average water warming or below-average water cooling, excess of suspended sediments, organic pollution, and physical damage inflicted by fish bites, anchors, and other means. Clionids do not seem to produce toxic compounds that affect virile coral colonies and are repelled by healthy coral polyps. Overgrowth is accomplished by excavating coral calyces from below the surface, thus depriving the polyps of their support, or by covering skeletons of dying coral. Overpowering corals by bioerosion is a successful competitive mechanism that works also on unstressed coral, albeit at a much slower pace. On the other hand, also non-boring encrusting sponges may overgrow coral by lateral spreading, for instance the symbiotic (with cyanobacteria) species of Chondrilla and Terpios, particularly if sponge growth is stimulated and coral resistance weakened by elevated levels of pollution. There are indications that encrusting clionids and other sponges may dramatically change the community structure and physical stability of shallow reefs that are readily compromised by natural or anthropogenic pressures.Algunas especies de esponjas perforantes de carbonatos (Clionidae, Hadromerida) cubren el substrato calcáreo como una costra delgada y continua, similar a un revestimiento (estadio beta). Esta película de tejido es el resultado de la fusión de las inicialmente aisladas papilas incurrentes y excurrentes que son la característica morfológica común y de mayor longevidad de muchas otras representantes de la familia. En el Atlántico occidental tropical y subtropical, por lo menos cuatro especies de cliónidas incrustan los esqueletos del coral arrecifal (Scleractinia, Hydrozoa): Cliona caribbaea CARTER (incluyendo C. aprica PANG y C. langae PANG), C. delitrix PANG, C. lampa de LAUBENFELS, y C. varians (DUCHASSAING y MICHELOTTI) (=Anthosigmella varians de los autores). Un carácter conspicuo de estas esponjas incrustantes es que muchas ribetean el coral vivo o cubren el coral recién muerto, como queda indicado por el contorno claro de la estructura de coral calicular bajo el fino revestimiento de la esponja. Los experimentos de campo y el estudio histológico sobre Cliona caribbaea en Belize y Cliona lampa en Bermudas muestran que las esponjas dominan el coral que se encuentra bajo estrés, creciendo sobre él a una velocidad rápida. Los parámetros de estrés incluyen periodos amplios de aguas con temperaturas tanto por encima como por debajo de la media, exceso de sedimentos en suspensión, contaminación orgánica, y lesiones físicas infligidas por mordiscos de peces, anclas u otros medios. No parece que las cliónidas produzcan componentes tóxicos que afecten las colonias coralinas vigorosas y los pólipos coralinos sanos las repelen. El sobrecrecimiento se lleva a cabo mediante la excavación en los cálices coralinos desde debajo de la superficie, privando de esta manera a los pólipos de su soporte, o cubriendo los esqueletos de coral muerto. El ataque a los corales mediante bioerosión es un mecanismo competitivo eficaz que funciona también en corales no estresados, si bien a un ritmo mucho más lento. Por otra parte, las esponjas no perforantes también pueden sobrecrecer el coral por expansión lateral, como hacen por ejemplo las especies simbiontes (con cianobacterias) de Chondrilla y Terpios, en especial si los niveles de contaminación altos estimulan el crecimiento de la esponja y reducen la resistencia del coral. Existen indicios de que las cliónidas incrustantes y otras esponjas pueden cambiar drásticamente la estructura de la comunidad y la estabilidad física de arrecifes someros que fácilmente se ven comprometidos por presiones naturales o antropogénicas

The Development of Egalitarianism, Altruism, Spite and Parochialism in Childhood and Adolescence

We study how the distribution of other-regarding preferences develops with age. Based on a set of allocation choices, we can classify each of 717 subjects, aged 8 to 17 years, as either egalitarian, altruistic, or spiteful. Varying the allocation recipient as either an in-group or an out-group member, we can also study how parochialism develops with age. We find a strong decrease in spitefulness with increasing age. Egalitarianism becomes less frequent, and altruism much more prominent, with age. Women are more frequently classified as egalitarian than men, and less often as altruistic. Parochialism first becomes significant in the teenage years.other-regarding preferences, egalitarianism, altruism, spite, parochialism, experiments with children and adolescents

Impact of Crustose Clionid Sponges on Caribbean Reef Corals

Live and dead thalli of crustose coralline algae were examined to evidentiate their endolithic flora. As it occurs in corals, there is a great difference between endolithic microorganisms observed in live thalli and those observed in dead thalli. During our study live thalli were found to have few (Plectonema terebrans and Ostreobium quekettii) or no endolithic microorganisms, whereas a more numerous number of microorganisms (cyanobacteria, chlorophyta and fungi) was found in dead thalli. Some species of limestone-excavating Porifera (Clionidae, Hadromerida) cover their substrate as a thin, continuous, veneer-like crust (beta stage). This film of tissue is the result of fusion of the initially discrete incurrent and excurrent papillae (alpha stage) that are the common and lifelong morphological feature of most other representatives of the family. In the tropical and subtropical western Atlantic, at least four species of clionids encrust reef-coral skeletons (Scleractinia, Hydrozoa): Cliona caribbaea CARTER (including C. aprica PANG and C. langae PANG), C. delitrix PANG, C. lampa de LAUBENFELS, and C. varians (DUCHASSAING and MICHELOTTI) (=Anthosigmella varians of authors). One conspicuous feature of these encrusting sponges is that many border live coral or cover recently dead coral as indicated by the clear outline of the coral calicular structure under the thin sponge veneer. Field experiments and histological study conducted on Cliona caribbaea in Belize and Cliona lampa in Bermuda indicate that the sponges overpower stressed coral which they overgrow at a fast rate. Stress parameters include extended periods of above-average water warming or below-average water cooling, excess of suspended sediments, organic pollution, and physical damage inflicted by fish bites, anchors, and other means. Clionids do not seem to produce toxic compounds that affect virile coral colonies and are repelled by healthy coral polyps. Overgrowth is accomplished by excavating coral calyces from below the surface, thus depriving the polyps of their support, or by covering skeletons of dying coral. Overpowering corals by bioerosion is a successful competitive mechanism that works also on unstressed coral, albeit at a much slower pace. On the other hand, also non-boring encrusting sponges may overgrow coral by lateral spreading, for instance the symbiotic (with cyanobacteria) species of Chondrilla and Terpios, particularly if sponge growth is stimulated and coral resistance weakened by elevated levels of pollution. There are indications that encrusting clionids and other sponges may dramatically change the community structure and physical stability of shallow reefs that are readily compromised by natural or anthropogenic pressures

Strategic Sophistication of Adolescents: Evidence from Experimental Normal-Form Games

We examine the strategic sophistication of adolescents, aged 10 to 17 years, in experimental normal-form games. Besides making choices, subjects have to state their first- and second-order beliefs. We find that choices are more often a best reply to beliefs if any player has a dominant strategy and equilibrium payoffs are not too unequal. Using a mixture model we can estimate for each subject the probability to be any of eight different strategic and non-strategic types. The econometric estimation reveals that older subjects are more likely to eliminate dominated strategies, and that subjects with good math grades are more strategic.strategic thinking, beliefs, experiment, age, adolescents

Impatience and Uncertainty: Experimental Decisions Predict Adolecents' Field Behavior

We study risk attitudes, ambiguity attitudes, and time preferences of 661 children and adolescents, aged ten to eighteen years, in an incentivized experiment. We relate experimental choices to field behavior. Experimental measures of impatience are found to be significant predictors of health related field behavior and saving decisions. In particular, more impatient children and adolescents are more likely to spend money on alcohol and cigarettes, have a higher body mass index (BMI) and are less likely to save money. Experimental measures for risk and ambiguity attitudes are only weak predictors of field behavior

Impatience and Uncertainty: Experimental Decisions Predict Adolescents' Field Behavior

We study risk attitudes, ambiguity attitudes, and time preferences of 661 children and adolescents, aged ten to eighteen years, in an incentivized experiment and relate experimental choices to field behavior. Experimental measures of impatience are found to be significant predictors of health-related field behavior, saving decisions and conduct at school. In particular, more impatient children and adolescents are more likely to spend money on alcohol and cigarettes, have a higher body mass index, are less likely to save money and show worse conduct at school. Experimental measures for risk and ambiguity attitudes are only weak predictors of field behavior.experiments with children and adolescents, risk, ambiguity, time preferences, health status, savings, conduct at school, external validity

Two temperature-compensated thermistor current meters for use in marine ecology

Small bead thermistors of the type commonly used for temperature measurement can be adapted for use as current probes in liquid or gaseous media. The small size, the rapid response, and the sensitivity of such probes make them well suited for the study of water movement as a microclimatic factor in marine and limnic habitats...

Impatience and Uncertainty: Experimental Decisions Predict Adolescents' Field Behavior

We study risk attitudes, ambiguity attitudes, and time preferences of 661 children and adolescents, aged ten to eighteen years, in an incentivized experiment. We relate experimental choices to field behavior. Experimental measures of impatience are found to be significant predictors of health related field behavior and saving decisions. In particular, more impatient children and adolescents are more likely to spend money on alcohol and cigarettes, have a higher body mass index (BMI) and are less likely to save money. Experimental measures for risk and ambiguity attitudes are only weak predictors of field behavior.experiments with children and adolescents, risk, ambiguity, time preferences, health status, savings, external validity, field behavior

Social Preferences in Childhood and Adolescence: A Large-Scale Experiment

Social preferences have been shown to be an important determinant of economic decision making for many adults. We present a large-scale experiment with 883 children and adolescents, aged eight to seventeen years. Participants make decisions in eight simple, one-shot allocation tasks, allowing us to study the distribution of social preference types across age and across gender. Our results show that when children and teenagers grow older, inequality aversion becomes a gradually less prominent motivating force of allocation decisions. At the same time, efficiency concerns increase in importance for boys, and maximin-preferences turn more important in shaping decisions of girls.children, social preferences, age, gender, experiment