Suchergebnisse

We study a collective decision-making process in which people interested in an issue may participate, at a cost, in a meeting, and the resulting decision is a compromise among the participants' preferences. We show that the equilibrium number of participants is small and their positions are extreme, and when the compromise is the median, the outcome is likely to be random. The model and its equilibria are consistent with evidence on the procedures and outcomes of U.S. regulatory hearings. (JEL D7, H0, L5)

We investigate the effect of climate change on population growth in 18th and 19th century Iceland. We find that annual temperature changes help determine the population growth rate in pre-industrial Iceland: a year 1 degree Celsius cooler than average drives down population growth rates by 1.14%. We also find that 18th and 19th century Icelanders adapt to prolonged changes in climate after 20 years. These adaptations reduce the short run effect of annual change in temperature by about 60%. Finally, a 1 degree Celsius sustained decrease in temperature decreases the steady state population by 10% to 26%.

Abstract
Social learning is a critical adaptation for dealing with different forms of variability. Uncertainty is a severe form of variability where the space of possible decisions or probabilities of associated outcomes are unknown. We identified four theoretically important sources of uncertainty: temporal environmental variability; payoff ambiguity; selection-set size; and effective lifespan. When these combine, it is nearly impossible to fully learn about the environment. We develop an evolutionary agent-based model to test how each form of uncertainty affects the evolution of social learning. Agents perform one of several behaviours, modelled as a multi-armed bandit, to acquire payoffs. All agents learn about behavioural payoffs individually through an adaptive behaviour-choice model that uses a softmax decision rule. Use of vertical and oblique payoff-biased social learning evolved to serve as a scaffold for adaptive individual learning – they are not opposite strategies. Different types of uncertainty had varying effects. Temporal environmental variability suppressed social learning, whereas larger selection-set size promoted social learning, even when the environment changed frequently. Payoff ambiguity and lifespan interacted with other uncertainty parameters. This study begins to explain how social learning can predominate despite highly variable real-world environments when effective individual learning helps individuals recover from learning outdated social information.

In 12 kurzen, unabhängigen Beiträgen setzen sich die verschiedenen Autoren mit der von Bourn und Wint präsentierten Untersuchung auseinander, die neben Anerkennung auch Kritik sowohl hinsichtlich der Untersuchungsmethode, der Datenzusammenstellung, als auch der Interpretation der Ergebnisse erfährt. Aus unterschiedlichen Blickwinkeln werden in den einzelnen Beiträgen jeweils Teilaspekte herausgegriffen und zusammen mit ergänzenden Informationen diskutiert. Hierbei wird deutlich, daß der Zusammenhang zwischen stärkerer Besiedlung, intensiverem Ackerbau und vermehrter Tierhaltung nicht generell für Afrika zutrifft. Dort, wo diese Faktoren zusammenfallen, sind sie z.T. mit komplexen sozio-ökonomischen Wandlungsprozessen verbunden; wie etwa in Kenia, wo sich ein Übergang zum Privateigentum an Grund und Boden vollzieht und die traditionelle Weidewirtschaft gegenüber dem "mixed farming" zurückgedrängt wird. Die Frage, inwieweit die Ergebnisse der Studie von Bourn und Wint die "Boserup Hypothese" tatsächlich bestätigen, wird in den einzelnen Beiträgen unterschiedlich bewertet. Im letzten Beitrag nehmen die beiden Autoren noch einmal selbst Stellung zu Fragen und Kritik bezüglich ihrer Arbeit. (DÜI-Ply)

Moral injury is closely associated with posttraumatic stress disorder (PTSD) and characterized by disturbances in social and moral cognition. Little is known about the neural underpinnings of moral injury, and whether the neural correlates are different between moral injury and PTSD. A sample of 26 U.S. military veterans (two females: 28–55 years old) were investigated to determine how subjective appraisals of morally injurious events measured by Moral Injury Event Scale (MIES) and PTSD symptoms are differentially related to spontaneous fluctuations indexed by amplitude of low frequency fluctuation (ALFF) as well as functional connectivity during resting-state functional magnetic resonance imaging scanning. ALFF in the left inferior parietal lobule (L-IPL) was positively associated with MIES subscores of transgressions, negatively associated with subscores of betrayals, and not related with PTSD symptoms. Moreover, functional connectivity between the L-IPL and bilateral precuneus was positively related with PTSD symptoms and negatively related with MIES total scores. Our results provide the first evidence that morally injurious events and PTSD symptoms have dissociable neural underpinnings, and behaviorally distinct subcomponents of morally injurious events are different in neural responses. The findings increase our knowledge of the neural distinctions between moral injury and PTSD and may contribute to developing nosology and interventions for military veterans afflicted by moral injury.

"Developing-country rangelands are vast and diverse. They are home to millions who are often poor, politically marginalized, and dependent on livestock for survival. Here we summarize our experiences from six case-study sites in sub-Saharan Africa, central Asia, and Latin America generally covering the past 25 years. We examine issues pertaining to population, natural resource management, climate, land use, livestock marketing, social conflict, and pastoral livelihoods. The six study sites differ with respect to human and livestock population dynamics and the resulting pressures on natural resources. Environmental degradation, however, has been commonly observed. Climate change is also having diverse systemic effects often related to increasing aridity. As rangelands become more economically developed pastoral livelihoods may diversify, food security can improve, and commercial livestock production expands, but wealth stratification widens. Some significant upgrades in rural infrastructure and public service delivery have occurred; telecommunications are markedly improved overall due to widespread adoption of mobile phones. Pressures from grazing, farming, mining, and other land uses-combined with drought-can ignite local conflicts over resources, although the intensity and scope of conflicts markedly varies across our case-study sites. Pastoralists and their herds have become more sedentary overall due to many factors, and this can undermine traditional risk-management tactics based on mobility. Remote rangelands still offer safe havens for insurgents, warlords, and criminals especially in countries where policing remains weak; the resulting civil strife can undermine commerce and public safety. There has been tremendous growth in knowledge concerning developing-country rangelands since 1990, but this has not often translated into improved environmental stewardship or an enhanced wellbeing for rangeland dwellers. Some examples of demonstrable impact are described, and these typically have involved longer-term investments in capacity building for pastoralists, local professionals, and other stakeholders. Research is shifting from ecologically centered to more human-centered issues; traditional academic approaches are often being augmented with participatory, community-based engagement. Building human or social capital in ways that are integrated with improved natural resource stewardship offers the greatest returns on research investment. Our future research and outreach priorities include work that fortifies pastoral governance, enhances livelihoods for a diverse array of rangeland residents, and improves land and livestock management in a comprehensive social-ecological systems approach."