Extremes of Markov chains with tail switching potential

Summary.  A recent advance in the utility of extreme value techniques has been the characteri- zation of the extremal behaviour of Markov chains. This has enabled the application of extreme value models to series whose temporal dependence is Markovian, subject to a limitation that prevents switching between extremely high and extremely low levels. For many applications this is sufficient, but for others, most notably in the field of finance, it is common to find series in which successive values switch between high and low levels. We term such series Markov chains with tail switching potential, and the scope of this paper is to generalize the previous theory to enable the characterization of the extremal properties of series displaying this type of behaviour. In addition to theoretical developments, a modelling procedure is proposed. A simulation study is made to assess the utility of the model in inferring the extremal dependence structure of autoregressive conditional heteroscedastic processes, which fall within the tail switching Markov family, and generalized autoregressive conditional heteroscedastic processes which do not, being non-Markov in general. Finally, the procedure is applied to model extremal aspects of a financial index extracted from the New York Stock Exchange compendium.     

A hazard model of the probability of medical school drop-out in the UK

Summary.  From individual level longitudinal data for two entire cohorts of medical students in UK universities, we use multilevel models to analyse the probability that an individual student will drop out of medical school. We find that academic preparedness—both in terms of previous subjects studied and levels of attainment therein—is the major influence on withdrawal by medical students. Additionally, males and more mature students are more likely to withdraw than females or younger students respectively. We find evidence that the factors influencing the decision to transfer course differ from those affecting the decision to drop out for other reasons.     

The Development of Intergroup Forgiveness in Northern Ireland

As societies like Northern Ireland, Israel, and South Africa strive to resolve social conflict, there is growing theoretical and empirical interest in the role of intergroup forgiveness. This study examined intergroup forgiveness among 340 young adults in Northern Ireland. A short form of the Enright Forgiveness Inventory explored possible influences on propensity to forgive. All participants were Catholic and female (mean age 17.36 years), and had experienced verbal or physical injury or bereavement due to the Northern Irish political violence. Overall forgiveness levels were low in comparison with previous studies of interpersonal forgiveness but similar to previous studies of intergroup forgiveness in Northern Ireland. The strongest (negative) predictor of forgiveness was the perceived degree of hurt caused by the injury .     

Facial expression in the presence of friends and strangers

This study investigated the effect of the physical presence of a friend or of a stranger on facial expressiveness. Pairs of friends and pairs of strangers (all women) were unobtrusively videotaped while they viewed together a number of emotional stimulus slides, and rated their individual emotional responses to them. Judges subsequently attempted to identify from the videotapes the emotions reported by each sender subject. Generally, expressions were more readily identified for women videotaped with friends than for those recorded with strangers. These results support the suggestion that the degree to which emotions are expressed depends on the role of an accompanying person. Altemative interpretations of this view are discussed.We thank Alan Fridlund and an anonymous reviewer for comments on a previous version of this paper.     

AN ETHNOGRAPHY OF COUPLE AND THERAPIST EXPERIENCES IN REFLECTING TEAM PRACTICE

Couple and therapist perspectives about the use and process of reflecting team practice were analyzed using ethnographic research. A domain analysis was performed on postession interviews from both couples and therapists, and on field notes from each therapist. Seven couples and five therapists were interviewed at least twice over a 4-month period concerning their reactions to and perceptions of reflecting team practice. Six domains concerning reflecting team practice emerged from the analysis: (a)benefits of its use, (b) effects of gender, (c)recommended use, (d) contraindicated use, (e) the importance of creating spatial separateness between couple and team members, and (f) sequences of communication between the couple and team members that elicit change. The latter two domains described the process of reflecting team practice (i.e., steps in how it is used and how it is implemented). The role of ethnog rahy in reflecting team practice and in family therapy research is discussed.     

Early Word Segmentation by Infants and Toddlers With Williams Syndrome

This study tested the ability of English infants and toddlers with Williams syndrome to segment, that is, to extract from fluent speech, bisyllabic nouns that had either a strong–‐weak stress pattern (predominant in English), or a weak–‐strong stress pattern. The testing procedure was the same for both types of words: Children were familiarized with instances of isolated nouns, and then tested on their recognition of these nouns embedded in passages. In English, typically developing infants start segmenting strong–‐weak nouns by 7.5 months of age, and weak–‐strong nouns by 10.5 months. Our clinical population was able to segment strong–‐weak nouns, but failed, despite chronological ages above 15 months, to segment weak–‐strong words. These results suggest that the development of word segmentation is seriously delayed in Williams syndrome. This deficit in early phonological processing may contribute to a fuller understanding of the late lexical onset in this population, a phenomenon that had hitherto only been explained in terms of cognitive and semantic deficits.     

Bayesian methods for generalized linear models with covariates missing at random

The authors propose methods for Bayesian inference for generalized linear models with missing covariate data. They specify a parametric distribution for the covariates that is written as a sequence of one‐dimensional conditional distributions. They propose an informative class of joint prior distributions for the regression coefficients and the parameters arising from the covariate distributions. They examine the properties of the proposed prior and resulting posterior distributions. They also present a Bayesian criterion for comparing various models, and a calibration is derived for it. A detailed simulation is conducted and two real data sets are examined to demonstrate the methodology.     

AN EXACT CONDITIONAL TEST FOR COVARIANCE SELECTION MODELS

An exact conditional test is developed for testing the absence of an edge in a graphical covariance selection model and is shown to be equivalent to a test based on the partial correlation coefficient. An example is given.     

Transnational social movement organisations in the global political arena

The post-Cold War period has been a time of rapid change in the international system. One major shift is a dramatic increase in the demands placed upon the United Nations. This increased reliance on the UN suggests that there may be a shift in opportunities for this and other international institutions to have a greater effect on the dynamics of global politics than was possible under the bi-polar system of the past. What are the implications of these changes for nongovernmental actors in the global system? We focus on a subset of international non-governmental organisations called transnational social movement organisations (TSMOs), and begin to document their forms and activities in the global arena. In what ways are TSMOs similar to or different from national social movement organisations, and how do TSMOs organise to engage in transnational political efforts? How do TSMOs interact with international institutions? Our analysis consists of detailed, systematic comparisons among seven TSMOs in the human rights, environmental, peace and development issue arenas, including: Amnesty International, Friends of the Earth, Greenpeace, International Fellowship of Reconciliation, Oxfam, Peace Brigades International and War Resisters International. We examine five dimensions of variation: founding and mission; leadership structure; membership; resources; and tactics. This work builds on the earlier work of Dennis Young (1992) and helps to inform future research in this area.