Peer Effects in Risk Taking

This paper examines the effect of peers on individual risk taking. In the absence of informational motives, we investigate why social utility concerns may drive peer effects. We test for two main channels: utility from payoff differences and from conforming to the peer. We show experimentally that social utility generates substantial peer effects in risk taking. These are mainly explained by utility from payoff differences, in line with outcomebased social preferences. Contrary to standard assumptions, we show that estimated social preference parameters change significantly when peers make active choices, compared to when lotteries are randomly assigned to them

Distribution and biogeography of Central American howling monkeys (Alouatta pigra and A. palliata)

Central America has two howling monkey species: the widespread mantled howling monkey (Alouatta palliata) and the endemic and endangered black howling monkey (A. pigra) limited to southeastern Mexico, northern Guatemala and Belize. Studies that verify the distribution of these species are needed, especially in their contact zones where sympatry is reported. Their evolutionary history remains controversial. My study examines their distribution at a local scale in a potential contact zone in eastern Guatemala through direct observations and interviews and at a regional scale across the entire isthmus using data from museum specimen localities, study sites, historic records and field surveys. Using GIS I analyzed the distributions against geographic and ecological features to infer current barriers between both species and explore the possibility of their role in the initial speciation. I found no evidence for current sympatry in eastern Guatemala; instead parapatry is maintained by a riverine barrier and by ecological adaptation, as only A. pigra occurs in the cold montane habitats further inland. My study reveals broader elevational and vegetational tolerances by A. pigra than previously reported. My results suggest differences in elevation and cold tolerances by the two species which I consider an important ecological barrier separating them at present. I identified the highland massif of northern Central America and their associated coniferous and subalpine vegetation as a geographic barrier. In contrast to other studies, I propose that both species ranges are not adjacent throughout, but separated by these mountains and only coming into contact in a broad sympatry zone in the lowlands north of the highland massif in Mexico and in the narrow parapatry zone in Guatemala. I present an alternative biogeographic hypothesis that proposes an initial split by the northern Central American highland massif during cold periods that resulted in the isolation of the A. pigra lineage in the Yucatan peninsula and in the further divergence in cold tolerance

The Influence of Fluorine, Chlorine and Water on the Rheology and Structure of Na2O-CaO-Al2O3-SiO2 Melts

In dieser Studie wurde der alleinige und gemeinsame Einfluss von 1.6 bis 14.5 mol% Wasser, 1.1 bis 18.3 mol% Fluor (F) und 0.5 bis 1.4 mol% Chlor (Cl) auf die Struktur und Viskosität von peralkalinen und peraluminösen Na2O CaO Al2O3 SiO2 Gläsern und Schmelzen mit ~ 66 mol% SiO2 (auf volatilfreier Basis) untersucht. Die Zusammensetzung der peralkalinen Proben entspricht einem Modellsystem für Phonolithschmelzen. Die wasserfreien Proben wurden in 1 atm Öfen aus Oxid und Karbonatverbindungen sowie Halogeniden hergestellt. Die wasserhaltigen peralkalinen Proben wurden in einer innenbeheizten Gasdruckanlage und die wasserhaltigen peraluminösen Proben in einer Stempelzylinderpresse hergestellt. Die Viskosität der Proben wurde mit der Mikropenetrationstechnik (108.5 1013 Pa s) und der „parallel plate“ Methode (105.5 Pa s 109 Pa s) gemessen. Die Struktur der Gläser wurde mittels „magic angle spinning“ (MAS) Kernspinresonanzspektroskopie (NMR) anhand der Nuklide 19F, 23Na, 27Al, 29Si and 35Cl analysiert. Fluor und Wasser allein oder in Kombination verringern die Viskosität der Schmelzen, wobei der Effekt von Wasser stärker ist als der von F. Beide Volatile verringern die Viskosität von peraluminösen Schmelzen stärker als in den peralkalinen Schmelzen. Für die peralkalinen Schmelzen wurde eine Verringerung der Viskosität durch F bis zu einer Konzentration von 1.9 mol% F festgestellt, jedoch für eine Konzentration von 6.2 mol% F wurde keine weitere Verringerung der Viskosität festgestellt. In den peraluminösen Schmelzen hingegen wurde bis zu einer Konzentration von 18.3 mol% F ein stetiger Abfall der Viskosität mit zunehmendem Fluorgehalt beobachtet. Der gemeinsame Einfluss von F und Wasser ist auf Grund ihrer jeweiligen Einzeleffekte geringer als angenommen, was zeigt, dass die Effekte von F und Wasser auf die Viskosität nicht unabhängig voneinander sind. Der zusammensetzungs und konzentrationsabhängige Effekt von F auf die Viskosität der Schmelzen stimmt mit Unterschieden im Einbaumechanismus von F überein. 19F MAS NMR Spektren zeigen, dass in den peralkalinen Gläsern F sowohl in „salzartigen“ F Ca(n) und F Na(n) als auch in nicht brückenbildenden Si F Na(n), Al F Ca(n), Al F Na(n) und brückenbildenden Al F Al Umgebungen vorkommt („n“ bedeutet, dass die Anzahl der Atome unklar oder variabel ist). F Ca(n) ist die am häufigsten vorkommende Umgebung, obwohl Ca das am wenigsten häufige Kation in den Proben ist. In den peraluminösen Gläsern existiert F nur in Si F und Al F Umgebungen, wobei Al F Na(n) die am häufigsten vorkommende Umgebung ist. Die Bildung von salzartigen F Ca(n) und F Na(n) Umgebungen sollte zu einem Anstieg der Viskosität durch eine Verringerung der netzwerkmodifizierenden Kationen führen. Die Bildung von Si F und Al F Umgebungen sollte die Viskosität entweder auf Grund einer Reduzierung von brückenbildenden Sauerstoffen durch nicht brückenbildende F oder durch einen Austausch von brückenbildenden Sauerstoffen durch brückenbildende F, welche eine niedrigere Bindungsstärke haben, verringern. Daraus lässt sich schließen, dass F die Viskosität in peralkalinen Schmelzen weniger stark verringert als in peraluminösen Schmelzen, weil F in den peralkalinen Schmelzen in Umgebungen existiert, welche die Viskosität erhöhen oder erniedrigen können, während F in den peraluminösen Schmelzen nur in Umgebungen existiert, welche die Viskosität verringern. Der konzentrationsabhängige Einfluss von F auf die Viskosität in den peralkalinen Schmelzen scheint in Zusammenhang mit einer Änderung in der Fluorspeziation zu stehen: Der relative Anteil von F Ca(n) Umgebungen, von denen anzunehmen ist, dass sie die Viskosität erhöhen, steigt von 42 auf 53% bei einem Anstieg im F Gehalt von 1.2 auf 6.2 mol% F. Veränderungen in der Fluorspeziation scheinen ebenfalls verantwortlich dafür zu sein, dass der Effekt von F und Wasser in Kombination geringer ist als erwartet. 19F MAS NMR Spektren von fluor und wasserhaltigen Proben zeigen, dass der relative Anteil von Al F Umgebungen, von denen anzunehmen ist, dass sie die Viskosität verringern, mit zunehmendem Wassergehalt abnimmt und dass im Gegenzug der relative Anteil von F Ca(n) Umgebungen zunimmt. Mit IR Spektroskopie wurde in den peralkalinen Proben kein Unterschied im OH/H2O Verhältnis bei gleichem Gesamtwassergehalt durch die Präsenz von F beobachtet. Im Gegensatz dazu gibt es starke Hinweise darauf, dass F in den peraluminösen Proben das OH/H2O Verhältnis bei gleichem Gesamtwassergehalt verringert, was erklären würde, weshalb F und Wasser in Kombination die Viskosität weniger verringern als von ihren Einzeleffekten zu erwarten wäre. Der Einfluss von Cl auf die Viskosität und Struktur der Schmelzen und Gläser ist sehr unterschiedlich verglichen mit F. Cl erhöht die Viskosität in den peralkalinen Schmelzen und verringert die Viskosität in den peraluminösen Schmelzen. Viskositätsmessungen von wasserhaltigen, chlorfreien und chlorhaltigen peralkalinen Schmelzen zeigen, dass der Effekt von Cl auf die Viskosität nicht durch die Präsenz von Wasser beeinflusst wird. Das beobachtete 35Cl NMR Signal zeigt, dass sowohl in den peralkalinen als auch in den peraluminösen Gläsern Cl in Na Ca Cl Umgebungen mit einem hohen Na Anteil existiert, was auf Grund des Ca/Na Verhältnisses von 1/5 zu erwarten war. Die Cl Umgebung in den peralkalinen und peraluminösen Gläsern ist ähnlich, jedoch beinhaltet die Cl Umgebung in den peraluminösen Gläsern mehr Ca. In den 35Cl MAS NMR Spektren wurde im Vergleich zu einem Natriumsilikatglas nur ein Teil des 35Cl NMR Signals der peralkalinen und der peraluminösen Proben beobachtet. Das fehlende Signal deutet darauf hin, dass ein Teil der Cl Atome in verzerrten oder ungeordneten Umgebungen existiert, welche eine Signalbreite haben, die zu groß ist, um mit den verwendeten NMR Spektroskopie Methoden gemessen werden zu können. Der Anstieg der Viskosität durch Cl in den peralkalinen Schmelzen kann dadurch erklärt werden, dass Cl die Anzahl der netzwerkmodifizierenden Kationen reduziert, während mehrere Möglichkeiten zur Diskussion stehen, weshalb Cl die Viskosität in peraluminösen Schmelzen verringert. Die Effekte von F und Cl auf die Viskosität sind unabhängig voneinander und summieren sich auf. Es wurde mit NMR Spektroskopie kein Hinweis dafür gefunden, dass F einen Einfluss auf den Einbaumechanismus von Cl hat

The process of conserving biodiversity: From planning to evaluating conservation actions on private land in the Cape Lowlands, South Africa

Conservation can be conceptualised as a process of linked phases that contribute to bringing about effective biodiversity protection: (i) a conservation assessment that identifies spatially explicit conservation priorities to provide strategic guidance on where best to invest conservation resources; (ii) a planning phase that takes the spatial priorities forward into implementation processes by setting out a strategy and schedule for undertaking conservation action; (iii) an implementation phase during which conservation interventions are executed; and (iv) an evaluation phase to investigate whether conservation has been successful. In practice, conservation is rarely conducted in this way. The interrelated phases are often undertaken separately, links are neglected, and conservation science to date has focused primarily on the conservation assessment. This has led to the development of highly sophisticated principles and techniques for locating priority conservation areas, but planning and evaluation have received limited research attention: few published studies demonstrate collaborative planning processes that assist with putting conservation assessments into practice, or show on-theground conservation success linked to effective conservation planning and implementation processes. My PhD research aimed to address these knowledge gaps by conducting a conservation assessment and collaborative planning phase that would lead to effective conservation action as determined by an evaluation. The study area was in the critically endangered Cape Lowlands, a conservation priority area in the Cape Floristic Region, South Africa. The highly transformed agricultural production landscape is mostly privately owned; formal biodiversity protection is low; and remnants of natural vegetation (< 9% is left) harbour an exceptionally diverse flora. Strategic conservation interventions coordinated across the Cape Floristic Region (CFR) provided the overall implementation context in the Cape Lowlands. My research was conducted in this real-world practical situation and addresses the whole conservation process, from assessment to evaluation of conservation actions. I first developed a conservation assessment guided by three key questions: âWhat are feasible, efficient, defensible and efficacious solutions for (i) deriving a surrogate layer that represents biodiversity in a region which is characterised by exceptional plant species richness and endemism ; and (ii) considering the connectivity of natural areas in an ecosystem that is highly transformed, fragmented and largely unprotected?â; and âHow can a selection method be developed for identifying and prioritising key biodiversity areas in a landscape identified as 100% irreplaceable?â To answer these questions I identified feasible, efficient, defensible methods focusing on three key aspects: (i) producing a biodiversity surrogate map of original vegetation cover using two alternative approaches: simple expert mapping and statistical modelling integrating plant species and environmental data; (ii) designing selection units based on vegetation connectivity in a simple technique to include spatial attributes of conservation areas before identifying key biodiversity areas; (iii) developing a prioritisation method based on a simple scoring system and verifying results with MARXAN-selected priority areas. In all vi three cases I found that the simple conservation assessment methods produced suitable outputs for further integration in the assessment and in decision-making during planning. (i) The expert map was as effective as the vegetation model and required fewer resources to be produced since the model relied on resource-intensive species data collection. (ii) In comparison with commonly used cadastre-based units, connectivity-based selection units captured connected vegetation more effectively and area-efficiently in units that served as the basis for priority area selection. (iii) Scoring provided a feasible, defensible mechanism for prioritising key biodiversity areas in the Cape Lowlands where all remaining vegetation has been identified as 100% irreplaceable. The planning phase complemented the assessment. Key guiding questions here were âHow can collaborative planning be used to translate the conservation assessmentâs technical outputs into timebased conservation goals and into useful products for implementation?â and âWhat constitutes effective planning in the conservation process? Through a collaborative scheduling process, I developed timebased conservation goals for action in the Cape Lowlands. This was undertaken in two work sessions with scientists, planners and conservation practitioners from the implementing agency, CapeNature. Scheduling was guided by (i) scoring-derived biodiversity-driven spatial priorities that made intuitive sense to implementers; and (ii) conservation opportunities and constraints (including resources) identified by the practitioners. Scheduling was conducted with reference to the on-going development of a private land conservation strategy for the CFR to be piloted in the Cape Lowlands. The scheduling process was an effective platform for taking spatial priorities from the assessment towards implementation: the discourse-based collaborative planning was constructive and led to consensusbased final products, including a 20-year and 5-year conservation plan setting out spatially explicit goals for conservation interventions in the Cape Lowlands. The main limitation of the process was that resource planning was not integrated explicitly enough to identify realistic goals. This highlighted the importance of integrating detailed resource considerations in future planning. Finally, to address the question âTo what extent has the Cape Lowlands conservation plan been implemented after five years of off-reserve conservation interventions in the region?â I developed a protocol for evaluating the effectiveness of conservation action in the Cape Lowlands. I assessed (i) the extent to which the goals conservation plans produced in the planning phase had been implemented; and (ii) the achievements of incentive-based conservation stewardship interventions on private land in the Cape Lowlands and CFR. Achievements were measured as hectares of vegetation protected through voluntary and legally-binding contractual conservation agreements between landowners and conservation organisations. The evaluation revealed that (i) CapeNatureâs stewardship interventions in the Cape Lowlands focused on priority areas identified in the 5- and 20-year conservation plans, thus demonstrating effective execution of the plans; (ii) private land conservation interventions have been remarkably successful and cost-effective: 68604ha priority vegetation were protected in the CFR under conservation agreements by end 2007, rivalling private land biodiversity conservation in the U.S.A. and Latin America, and more than 8000ha in the critically endangered Cape Lowlands at a cost of R 6.8 vii Million (< 1 million US$). The evaluation identified the long-term financial sustainability of current implementation programmes as the most significant threat to future success in private land conservation interventions in the Cape Lowlands and CFR. There is significant scope to design future monitoring and evaluation systems to measure ecological gains due to specific conservation actions, not done in the Cape Lowlands study, and to tailor approaches to suit specific programme stages. This PhD provides a rare overview of an entire conservation cycle with linked phases that has led to biodiversity protection. The study highlights that an effective long-term process demands significant investment in (i) a diverse (growing) set of skills and expertise to solve complex conservation situations; (ii) time, especially for visible implementation success; and (iii) well-allocated resources (money, time, skills, research attention) across all phases in the conservation process. This is necessary as each phase is needed to achieve the ultimate conservation goal: I show in the Cape Lowlands that a simple conservation assessment with limited funds (R1.8 million over 3 years) can be highly effective in guiding action towards priority areas. Important here is to develop rapid, defensible methods for cost-effective assessments and linking these with in-depth planning processes. Planning and evaluation in the Cape Lowlands were essential connecting phases that continue to support implementation success. In the context of on-going conservation action, planning and evaluation need to become part of a cyclical conservation process geared towards improved practices. I suggest that significantly greater investment in planning and evaluation research is essential to move conservation science forward in fulfilling its fundamental goal of strategically guiding where, when and how to invest optimally in conservation interventions. This will be exceptionally beneficial for undertaking effective conservation interventions and will help to clearly demonstrate the value of the research for conservation practice

Social anchor effects in decision-making under ambiguity

I experimentally examine whether feedback about others' choices provides an anchor for decision-making under ambiguity. In a between-subjects design I vary whether subjects learn choices made individually by a "peer" in a first part when facing the same task a second time, and whether prospects are defined over gains or losses. My key findings are that the relative ambiguity attitude (compared to the peer's) significantly matters for shifts in individual attitudes, and that dynamics considerably differ between gain and loss domains. For gains, learning to be comparably ambiguity averse increases the likelihood for such shifts, relative to the individual condition; for losses, this likelihood decreases only if peers learn to exhibit exactly the same attitude. Further, I observe imitative shifts towards the peer's attitude in the gain domain, but only towards neutrality in the loss domain. Shifts towards neutrality for losses also appear significant without social anchor suggesting that ambiguity seeking might not be particularly robust. Moreover, cognitive ability positively correlates to shifts towards neutrality in the gain domain, but has no impact in the loss domain