A general framework for path convexities

Journal of Combinatorial Optimization - In this work we deal with the so-called path convexities, defined over special collections of paths. For example, the collection of the shortest paths in a...     

Responsiveness to feedback as a personal trait

We investigate individual heterogeneity in the tendency to under-respond to feedback (“conservatism”) and to respond more strongly to positive compared to negative feedback (“asymmetry”). We elicit beliefs about relative performance after repeated rounds of feedback across a series of cognitive tests. Relative to a Bayesian benchmark, we find that subjects update on average conservatively but not asymmetrically. We define individual measures of conservatism and asymmetry relative to the average subject, and show that these measures explain an important part of the variation in beliefs and competition entry decisions. Relative conservatism is correlated across tasks and predicts competition entry both independently of beliefs and by influencing beliefs, suggesting it can be considered a personal trait. Relative asymmetry is less stable across tasks, but predicts competition entry by increasing self-confidence. Ego-relevance of the task correlates with relative conservatism but not relative asymmetry.     

Bayesian temporal density estimation with autoregressive species sampling models

We propose a novel Bayesian nonparametric (BNP) model, which is built on a class of species sampling models, for estimating density functions of temporal data. In particular, we introduce species sampling mixture models with temporal dependence. To accommodate temporal dependence, we define dependent species sampling models by modeling random support points and weights through an autoregressive model, and then we construct the mixture models based on the collection of these dependent species sampling models. We propose an algorithm to generate posterior samples and present simulation studies to compare the performance of the proposed models with competitors that are based on Dirichlet process mixture models. We apply our method to the estimation of densities for the price of apartment in Seoul, the closing price in Korea Composite Stock Price Index (KOSPI), and climate variables (daily maximum temperature and precipitation) of around the Korean peninsula.     

Discussion on the paper by Peter Müller,Fernando A. Quintana,and Garritt L. Page

The article by Müller, Quintana, and Page reviews a variety of Bayesian nonparametric models and demonstrates them in a few applications. They emphasize applications in spatial data on which our discussion focuses as well. In particular, we consider two types of mixture models based on species sampling models (SSM) for spatial clustering and apply them to the Chilean mathematics testing score data analyzed by the authors. We conclude that only the mixture model of SSM with spatial locations as part of observations renders spatially non-overlapping clusters.     

Generating inclusive services for children,youth and families: A shift to using complex systems theory

Service systems for children and families have been shaped by standard approaches to knowledge-building, which reflect a reductionist approach and assume linearity and/or that individuals and experiences are normally distributed. Yet, these approaches may be inadequate for clients most at-risk, especially those who would be analytic ‘outliers’. A complexity lens focuses on the whole system and seeks to identify patterns, including the dynamic interactions between components of the system. Social work scholars have begun to apply complexity theory to social work research efforts, demonstrating the conceptual potential of incorporating this theoretical approach into social work theories and models such as the person-in-environment framework and the ecosystems perspective. Yet, frameworks informed by complexity theory may require ontological and epistemological shifts in thinking and new methodological approaches in order to fully embody a complexity approach. Complexity theory offers the opportunity to consider social work clients who are most at-risk, as it is better suited for power law distributions. We can, therefore, reconceptualize the most ‘at-risk’ clients as being in a state of transition, which is also the space of most creativity and possibility.     

Influence of habitat type and distance from source area on bird taxonomic and functional diversity in a Neotropical megacity

The Neotropical region has been subjected to massive urbanization, which poses high risks for some global biodiversity hotspots and losses of ecosystem functions and services. In this study, we investigate how distance from large patches of native forests (source areas) and vegetation (green)/and infrastructure (gray) characteristics affect bird species richness and functional diversity in São Paulo megacity, southeastern Brazil. We analyzed the effects of source areas and green/gray characteristics on species richness and functional diversity (richness, evenness, and divergence) indices. We detected 231 bird species, and our data confirmed our predictions: (1) bird species richness in urbanized habitats was found to be (~?50–85%) lower than in source habitats; (2) species richness and trait composition significantly decreased as the distance from the source area increased, while functional richness was not affected by this metric; and (3) shrub and herbaceous covers and maximum height of trees were positively correlated with species richness and unique functional traits regarding habitat, diet, foraging and nesting strata and dispersal ability of birds in the forest-urban matrix. The number of buildings was negatively correlated with bird species richness and functional richness. Maximum height of buildings caused dramatic declines in functional evenness. Functional divergence was notably lower in sites with high shrub cover. Our study stresses the complexity of vegetation embedded in large Neotropical urban settlements and the need to maintain large protected areas surrounding megacities to mitigate the impacts of urbanization on birds.