Preference Formation, School Dissatisfaction and Risky Behavior of Adolescents

School dissatisfaction is an important component of the subjective well-being of adolescents associated with "risky behavior" like drug use, unprotected sex, norm violations and illegal behavior. We extend the standard human capital model to joint human investment (education) and disinvestment (risky behavior). Based on this model, we develop a general dynamic framework to analyze the preference formation of children and behavioral change at school. Once an educational norm is set by adults, children can rationally deviate from this norm, while staying at school, after experiencing bad surprises like a school failure. The same type of dynamic equation can be used in a sequence to predict education, satisfaction with school, and a host of risky behavior. We test these assumptions with a unique panel data set on American adolescents attending middle or high school. School dissatisfaction is found to have a significant positive effect upon nine different types of risky behavior.Education; Satisfaction; Risky behavior; Preference formation; Economic behavior of children

Communautés piscicoles introduites des lacs d’altitude : approches scientifiques et influences idéologiques

Les peuplements piscicoles introduits représentent une empreinte anthropique majeure de l’histoire biologique des lacs d’altitude. Basé sur un état de l’art, notre travail s’interroge sur la façon dont la production scientifique intègre cette composante ichtyologique introduite. L’étude limnologique de ces milieux se révèle profondément influencée par la façon dont le poisson est perçu et les trois courants mis en évidence témoignent d’une empreinte sociologique et idéologique forte dans les connaissances produites. Nous nous interrogeons donc sur la nécessité de repenser la place accordée aux peuplements piscicoles dans l’étude des lacs d’altitude

Preference Formation, School Dissatisfaction <br />and Risky Behavior of Adolescents

International audienceSchool dissatisfaction is an important component of the subjective well-being of adolescents associated with "risky behavior" like drug use, unprotected sex, norm violations and illegal behavior. We extend the standard human capital model to joint human investment (education) and disinvestment (risky behavior). Based on this model, we develop a general dynamic framework to analyze the preference formation of children and behavioral change at school. Once an educational norm is set by adults, children can rationally deviate from this norm, while staying at school, after experiencing bad surprises like a school failure. The same type of dynamic equation can be used in a sequence to predict education, satisfaction with school, and a host of risky behavior. We test these assumptions with a unique panel data set on American adolescents attending middle or high school. School dissatisfaction is found to have a significant positive effect upon nine different types of risky behavior

Changes in vertical and horizontal diversities mediated by the size structure of introduced fish collectively shape food‐web stability

International audienceAbstract Species introductions can alter local food‐web structure by changing the vertical or horizontal diversity within communities, largely driven by their body size distributions. Increasing vertical and horizontal diversities is predicted to have opposing effects on stability. However, their interactive effects remain largely overlooked. We investigated the independent and collective effects of vertical and horizontal diversities on food‐web stability in alpine lakes stocked with variable body size distributions of introduced fish species. Introduced predators destabilize food‐webs by increasing vertical diversity through food chain lengthening. Alternatively, increasing horizontal diversity results in more stable food‐web topologies. A non‐linear interaction between vertical and horizontal diversities suggests that increasing vertical diversity is most destabilizing when horizontal diversity is low. Our findings suggest that the size structure of introduced predators drives their impacts on stability by modifying the structure of food‐webs, and highlights the interactive effects of vertical and horizontal diversities on stability

Persisting in extreme environments: What are the drivers of body conditions of introduced fish in high mountain lakes?

International audienceAbstract Salmonids are introduced in various ecosystems, including mountain lakes characterised by extreme environmental constraints. Although these constraints can affect salmonid body condition through direct and indirect pathways, they remain seldom explored despite their importance for understanding salmonid fitness and long‐term establishment. In order to fill this gap, we firstly fitted species‐specific weight–length relationships for three salmonid species in nine mountain lakes, and compared their allometric coefficients with those of 362 salmonid populations worldwide to identify potential differences in growth trajectory of salmonids in the studied lakes. We then investigated how thermal characteristics and lake morphometry could influence salmonid body conditions, both directly and indirectly through salmonid density, the presence of forage fish and resource densities. We calculated salmonid relative body condition Kn and used a structural equation model (SEM) to disentangle these direct and indirect effects. The values of allometric coefficients for the three species did not differ from those of most salmonids worldwide although ontogenetic changes in Salvelinus alpinus weight gain was observed. Kn differed significantly among the populations studied. The strongest effects were related to direct and indirect effects of lake morphometry, while thermal characteristics had mostly indirect effects on Kn . The strength and the sign of the indirect effects of morphometry and temperature were mediated by the direct effects of resource and salmonid densities on Kn . Kn estimates were greater in lakes with shallow basin slopes than those with steep slopes. Shallow basin slopes probably provide habitats that support high prey availability and require lower energy expenditure by salmonids compared to lakes with steep slopes dominated by pelagic habitats. Complementarily, higher winter and summer temperatures favour Kn by supporting higher prey densities and longer periods of feeding activity. Our results may help managers to select lakes that optimise sustainability of salmonid populations based on the joint effects of basin morphometry and the expected thermal modifications induced by global change