Zero variance Markov chain Monte Carlo for Bayesian estimators

Interest is in evaluating, by Markov chain Monte Carlo (MCMC) simulation, the expected value of a function with respect to a, possibly unnormalized, probability distribution. A general purpose variance reduction technique for the MCMC estimator, based on the zero-variance principle introduced in the physics literature, is proposed. Conditions for asymptotic unbiasedness of the zero-variance estimator are derived. A central limit theorem is also proved under regularity conditions. The potential of the idea is illustrated with real applications to probit, logit and GARCH Bayesian models. For all these models, a central limit theorem and unbiasedness for the zero-variance estimator are proved (see the supplementary material available on-line).     

Influence of Perceived Economic Strain on the Relationship Between Caregiver BMI and Child BMI

As maternal BMI is a risk factor for higher child BMI, this exploratory study investigated perceived economic strain as a protective factor modifying this well-established relationship. Primary low-income female caregivers (n = 432) of preschoolers ages 3–5 years were interviewed using the Family Economic Strain Scale. Caregiver and child heights and weights were measured. Significant differences were found in perceived economic strain between normal versus underweight, overweight, and obese caregivers. A moderating effect approaching significance was noted such that at low levels of reported economic strain, caregiver BMI classification had no effect on child BMI z-score for normal weight, overweight, or obese caregivers. This study is the first to demonstrate that reduced perception of economic strain may act to buffer the impact of maternal overweight/obesity on child weight status. Given this biologically strong relationship, the potential for any modifiable factor to be detected is encouraging. Further collaborative research between economists and family resiliency researchers is suggested.     

Training Bodies,Building Status: Negotiating Gender and Age Differences in the U.S. Fitness Industry

What role does the body play in facilitating interaction across status differences? Whereas previous scholarly work has focused on “roles” and “specialized knowledge,” I investigate how bodies, appearances, and physical abilities are also consequential in these exchanges through the concept of “bodily capital.” Coined by Bourdieu, bodily capital provides a way to understand why individuals invest time, energy, and resources into their bodies, and what they expect to receive in return. As a concept, bodily capital is necessarily broad as it encompasses a variety of forms, including athletic prowess, attractiveness, physique, muscle tone/strength, agility, and other modes of embodiment. Because the body is integral to a variety of status distinction-making processes, individuals invest in and exchange bodily capital to increase their relative status in specific fields. Drawing on interviews with 26 personal trainers and 25 clients, as well as more than one year of participant observation, I find that trainers and clients use bodily capital to negotiate gender and age differences, either by re-arranging interactional power dynamics or resisting stereotypes. The type of bodily capital that allows for such negotiations to take place, however, is the hegemonic thin-toned ideal—a classed and largely raced form of bodily capital that has purchase in the U.S. fitness industry. Although individuals in the study were able to use this form of capital to enable successful cross-status interactions, doing so reified the dominance of middle-class, white bodily aesthetics. Thus, while bodily capital may challenge some status hierarchies, it reinforces others.     

A characterization of strategy-proof voting rules for separable weak orderings

We consider the problem of choosing a subset of a finite set of indivisible objects (public projects, facilities, laws, etc.) studied by Barberà et al. (1991). Here we assume that agents preferences are separable weak orderings. Given such a preference, objects are partitioned into three types, goods, bads, and nulls. We focus on voting rules, which rely only on this partition rather than the full information of preferences. We characterize voting rules satisfying strategy-proofness (no one can ever be better off by lying about his preference) and null-independence (the decision on each object should not be dependent on the preference of an agent for whom the object is a null). We also show that serially dictatorial rules are the only voting rules satisfying efficiency as well as the above two axioms. We show that the separable domain is the unique maximal domain over which each rule in the first characterization, satisfying a certain fairness property, is strategy-proof. I am grateful to Professor William Thomson for helpful comments and suggestions. I also thank Professor John Duggan, Christopher Chambers, and seminar participants in Department of Economics, University of Rochester. I thank anonymous referees for their detailed comments and suggestions that helped me a great deal to develop the earlier version of this paper. All remaining errors are mine.     

The effect of experience of childhood abuse among university students on self-perception and submissive behavior

Objective

The aim of this study was to investigate the effect of experience of childhood abuse among university students on self-perception and submissive behavior.

Methods

The study group consisted of 646 students attending various departments of the Karadeniz Technical University Faculty of Education in Trabzon, Turkey. Participants were administered the Childhood Trauma Questionnaire, the Social Comparison Scale and the Submissive Acts Scale in a classroom setting.

Results

Analysis revealed a significant negative correlation between self-perception and all forms of abuse (physical abuse, sexual abuse, and emotional abuse and neglect), and a positive correlation between submissive behavior and all forms of abuse. The students' emotional abuse and neglect scores varied significantly according to gender, with males having higher emotional abuse and neglect scores than those of girls. Additionally, males had higher physical abuse scores than girls.

Conclusion

Childhood abuse emerged as a significant predictor of negative self-perception and submissive behavior. In addition, with the exception of sexual abuse, other forms of abuse vary according to gender. The experiences of childhood abuse may have a long-term impact on various features of character and behavior.     

Achtsamkeit lernen im Offenen Dialog

Dialogue in the sense of David Bohm invites individuals and groups to consider together their ways of thinking and learning. By exploring mental models, which usually hinder reaching deeper agreement, this kind of dialogue opens new grounds and is, at the latest, since Peter Senge’;s management-bestseller “The fifth discipline” (1990), considered to be a basic process for team learning in groups and organisations. The article refers to university projects on ‘open dialogue’ with students at the universities of Oldenburg and Bochum between 2001–2003. Characteristics of “open dialogue” are represented as ways of attentiveness learning. Students practical reports are used to work out recommendations based upon “open dialogue” for the development of central deep ecology and human competences.     

Factors Contributing to Parents’ Preparation For Special-Needs Adoption

Three hundred and sixty-eight parents shared their perceptions of special-needs adoption preparation. Utilizing both quantitative and qualitative data to determine and understand what factors contribute to preparation, this study found that 12 child, family, and agency variables were correlated with perceived preparation, and that parents perceived level of preparation was predicted by the childs ability to attach, by the parents relationship with the agency, by the duration of the adoption, and by the parents ages at the time of adoption. Implications of these findings are discussed, as they relate to supporting parents, children, and families in special-needs adoptive placements.     

Interdisciplinary Insights on Nonverbal Responses within Attachment Relationships

As an extension of the thinking of Schachner, Shaver, and Mikulincer [2005, Journal of Nonverbal Behavior, 29], it is suggested that other disciplines (e.g., evolutionary psychology, social neuroscience) provide guidance with respect to factors that may influence nonverbal behavior within attachment relationships. An integration of biological and cognitive approaches provides a more complete understanding of the routes through which, and the extent to which, there is continuity between attachment processes in parent–child and adult relationships. As a specific illustration drawn from parent–child relationships, consideration is given to the cognitive biases more common among depressed or abusive mothers, and the resultant consequences for insecure attachment—as mediated by physiological stress responses and the ineffective communication processes that follow from those responses.     

Urban land cover decreases the occurrence of a wetland endemic mammal and its associated vegetation

Urbanization and other land cover changes have been particularly detrimental to wetlands throughout the planet. One wetland specialist that may be sensitive to land cover changes surrounding wetlands is the round-tailed muskrat (Neofiber alleni; hereafter RTM). The RTM is a wetland obligate rodent that appears to have declined over the last half century and is a species of concern in Florida, where it is a near endemic. To determine if urbanization or other land cover influenced the distribution of RTMs we took a multi-scaled approach to examine the occurrence of RTMs and their associated vegetation in North-Central Florida. We detected RTMs on 19 of 72 sample plots and used a Classification And Regression Tree (CART) to determine that dogfennel (Eupatorium capillifolium) was negatively associated with RTMs and maidencane (Panicum hemitomon) was positively associated with their occurrence on sampling plots. Examining the influence of landscape composition for 2 km surrounding our plots we found that RTM occurrence was negatively related to urban land cover. Further, we found that dogfennel increased and maidencane decreased as urbanization increased in the surrounding landscape. Our research suggests that conservation of RTMs and their associated vegetation should focus on limiting urban sprawl at least within 2 km of wetlands.     

Use of Poset Theory with Big Datasets: A New Proposal Applied to the Analysis of Life Satisfaction in Italy

The aim of this work is to propose a tool for measuring a complex concept, and to apply it to big sets of data measured on ordinal and/or dichotomous scales. An important field of application are subjective data, that are often based on opinions or personal evaluations. Many national and international surveys employ this kind of data, measured among thousand of individuals. Thanks to the use of the “average rank” as a synthetic measure of a complex concept, we believe that poset theory could be a very useful approach for dealing with ordinal data avoiding the use of scaling procedures. Because classic poset approaches are at their best when applied to few data at a time, our idea is based on a procedure for sampling units from a big population using a simple criterion to summarize the resulting values appropriately. Applying the central limit theorem enables a comparison of the results obtained from different groups using statistical tests on the means. We used our Height of Groups by Sampling (HOGS) method to compare the average rank among groups that are defined by one or more socio-demographic variables influencing the level of the complex concept we wish to measure. The application of the HOGS procedure to life satisfaction in Italy generated convincing results, revealing significant differences between regions, genders and levels of formal education. We compared the results given by HOGS with the non linear principal component analysis and obtain an easy readable output with convincing precision and accuracy; we are confident that the HOGS procedure can be applied to many other concepts investigated in the social sciences.