A spatial model for the needle losses of pine-trees in the forests of Baden-Württemberg: an application of Bayesian structured additive regression

Summary.  The data that are analysed are from a monitoring survey which was carried out in 1994 in the forests of Baden-Württemberg, a federal state in the south-western region of Germany. The survey is part of a large monitoring scheme that has been carried out since the 1980s at different spatial and temporal resolutions to observe the increase in forest damage. One indicator for tree vitality is tree defoliation, which is mainly caused by intrinsic factors, age and stand conditions, but also by biotic (e.g. insects) and abiotic stresses (e.g. industrial emissions). In the survey, needle loss of pine-trees and many potential covariates are recorded at about 580 grid points of a 4 km × 4 km grid. The aim is to identify a set of predictors for needle loss and to investigate the relationships between the needle loss and the predictors. The response variable needle loss is recorded as a percentage in 5% steps estimated by eye using binoculars and categorized into healthy trees (10% or less), intermediate trees (10–25%) and damaged trees (25% or more). We use a Bayesian cumulative threshold model with non-linear functions of continuous variables and a random effect for spatial heterogeneity. For both the non-linear functions and the spatial random effect we use Bayesian versions of P -splines as priors. Our method is novel in that it deals with several non-standard data requirements: the ordinal response variable (the categorized version of needle loss), non-linear effects of covariates, spatial heterogeneity and prediction with missing covariates. The model is a special case of models with a geoadditive or more generally structured additive predictor. Inference can be based on Markov chain Monte Carlo techniques or mixed model technology.     

Stability and Variability of Adolescents' Affiliation with Delinquent Friends: Predictors and Consequences

The effects of stability versus change in adolescents' affiliation with delinquent or nondelinquent friends over a two-year period (T1–T2) on delinquent behavior one year later (T3) were examined. In addition, T1 predictors of stability and change in the affiliation with delinquent or nondelinquent friends from T1 to T2 were assessed. Participants were 152 adolescents (77 girls, mean age 12.1 years at T1). Friends' delinquent behavior was assessed through friends' self-reports. The T1 predictor variables included adolescents' own delinquent behavior, attitude toward delinquent behavior, and parental monitoring. Adolescents' friendship affiliations at T2, but not at T1, predicted delinquent behavior at T3, suggesting a recency effect of friendship affiliation. Attitude toward delinquent behavior at T1 was the main predictor of stability versus change in adolescents' affiliation with delinquent or nondelinquent friends from T1 to T2.     

The Prevalence and Correlates of Multipartnered Fertility Among Urban U.S. Parents

Recent trends in marriage and fertility have increased the number of adults having children by more than 1 partner, a phenomenon that we refer to as multipartnered fertility. This article uses data from the Fragile Families and Child Wellbeing Study to examine the prevalence and correlates of multipartnered fertility among urban parents of a recent birth cohort (N = 4,300). We find that unmarried parents are much more likely to have had a child by a previous partner than married parents. Also, race/ethnicity is strongly associated with multipartnered fertility, as is mothers’ young age at first birth, and fathers’ history of incarceration. To the extent that childrearing across households diminishes parental resources, multipartnered fertility has important consequences for children’s well‐being.     

A relaxed approach to combinatorial problems in robustness and diagnostics

A range of procedures in both robustness and diagnostics require optimisation of a target functional over all subsamples of given size. Whereas such combinatorial problems are extremely difficult to solve exactly, something less than the global optimum can be ‘good enough’ for many practical purposes, as shown by example. Again, a relaxation strategy embeds these discrete, high-dimensional problems in continuous, low-dimensional ones. Overall, nonlinear optimisation methods can be exploited to provide a single, reasonably fast algorithm to handle a wide variety of problems of this kind, thereby providing a certain unity. Four running examples illustrate the approach. On the robustness side, algorithmic approximations to minimum covariance determinant (MCD) and least trimmed squares (LTS) estimation. And, on the diagnostic side, detection of multiple multivariate outliers and global diagnostic use of the likelihood displacement function. This last is developed here as a global complement to Cook’s (in J. R. Stat. Soc. 48:133–169, 1986) local analysis. Appropriate convergence of each branch of the algorithm is guaranteed for any target functional whose relaxed form is—in a natural generalisation of concavity, introduced here—‘gravitational’. Again, its descent strategy can downweight to zero contaminating cases in the starting position. A simulation study shows that, although not optimised for the LTS problem, our general algorithm holds its own with algorithms that are so optimised. An adapted algorithm relaxes the gravitational condition itself.     

Sticks and Stones: The Effects of Teasing on Psychosocial Functioning in an Overweight Treatment-seeking Sample

This self-report and observational study explores the relationship between perceptions of different kinds of teasing experiences and psychosocial functioning in an overweight treatment-seeking adolescent population. Participants were 96 adolescents enrolled in a residential weight-loss camp program. Prior to the start of treatment, participants' weight status was measured by trained program staff, and participants' perceptions of teasing experiences and psychosocial functioning were assessed through self-report questionnaires. Controlling for body mass index, more frequent and upsetting weight-related teasing experiences were associated with worse psychological functioning. Adolescents most distressed by weight-related teasing exhibited lower self-esteem and higher depressive symptoms regardless of reported frequency of weight-related teasing. Competence-related teasing was also associated with more worries about weight, greater depressive symptoms, and more negative anti-fat attitudes. Weight-related teasing, but not competence-related teasing, was associated with lower levels of program and social involvement for heavier adolescents.     

An Infinite Decision Puzzle

We tell a story where an agent who chooses in such a way as to make the greatest possible profit on each of an infinite series of transactions ends up worse off than an agent who chooses in such a way as to make the least possible profit on each transaction. That is, contrary to what one might suppose, it is not necessarily rational always to choose the option that yields the greatest possible profit on each transaction.     

Childhood maltreatment among Norwegian drug abusers in treatment

This article reports on the investigation of the correlation between the European Addiction Severity Index (EuropASI) and the Childhood Trauma Questionnaire (CTQ) among 102 Norwegian drug abusers admitted to treatment. The aim of the study is to explore how different types and levels of childhood trauma and social and psychiatric factors, medical situation and experienced family history are interrelated. The study addresses three main questions: 1) What is the prevalence of different kinds of childhood trauma among drug abusers in treatment? 2) Does type or level of maltreatment in childhood predict specific substance abuse problems as adults and/or specific social, psychiatric and medical problems as adults? 3) Do substance abuse problems and mental health problems in the primary family predict different types and levels of childhood maltreatment? Twenty‐five per cent of the total sample was included in the high‐level trauma group and 54% in the intermediate‐level group. Females had significantly higher scores than males in all types of childhood trauma. The strongest correlations were found between childhood trauma and lifetime psychiatric problems and psychiatric status during the last 30 days before admission for treatment. More research, and especially prospective studies, is needed to clarify the importance of parents' substance abuse and psychiatric problems in childhood/adolescent compared with trauma in the client's childhood and the client's current psychiatric status.     

Bayesian Analysis of DSGE Models—Rejoinder

We would like to thank all the discussants for their stimulating comments. While our article to a large extent reviews current practice of Bayesian analysis of Dynamic Stochastic General Equilibrium (DSGE) models the discussants provide many ideas to improve upon the current practice, thereby outlining a research agenda for the years to come. In our rejoinder we will briefly revisit some of the issues that were raised.