A generalization of Kristof's theorem on the trace of certain matrix products

Kristof has derived a theorem on the maximum and minimum of the trace of matrix products of the form \(X_1 \hat \Gamma _1 X_2 \hat \Gamma _2 \cdots X_n \hat \Gamma _n\) where the matrices \(\hat \Gamma _i\) are diagonal and fixed and theX _i vary unrestrictedly and independently over the set of orthonormal matrices. The theorem is a useful tool in deriving maxima and minima of matrix trace functions subject to orthogonality constraints. The present paper contains a generalization of Kristof's theorem to the case where theX _i are merely required to be submatrices of orthonormal matrices and to have a specified maximum rank. The generalized theorem contains the Schwarz inequality as a special case. Various examples from the psychometric literature, illustrating the practical use of the generalized theorem, are discussed.     

Some clarifications of the CANDECOMP algorithm applied to INDSCAL

Carroll and Chang have claimed that CANDECOMP applied to symmetric matrices yields equivalent coordinate matrices, as needed for INDSCAL. Although this claim has appeared to be valid for all practical purposes, it has gone without a rigorous mathematical footing. The purpose of the present paper is to clarify CANDECOMP in this respect. It is shown that equivalent coordinate matrices are not granted at global minima when the symmetric matrices are not Gramian, or when these matrices are Gramian but the solution not globally optimal.Part of this research has been supported by The Netherlands Organization for Scientific Research (NWO), PSYCHON-grant (560-267-011).     

The Dental Subscale of the Children's Fear Survey Schedule: Predictive Value and Clinical Usefulness

This study reports on the predictive value and clinical usefulness of the Dutch parental version of the Dental Subscale of the Children's Fear Survey Schedule (CFSS-DS). Parents of 718 children (4–12 years) completed this CFSS-DS version before or during the child's visit. The dentist rated the child's dental fear during treatment on a 5-point Likert-type Scale from 1 (not afraid at all) to 5 (very afraid). Reliability analysis was performed, and correlation coefficients between the two measures were calculated. The reliability of the scale proved to be high (Cronbach's = .93) and significant correlation coefficients were found (r = .58 and r = .68, p < .01). The negative predictive value of the CFSS-DS was high (.96), whereas its positive predictive value was relatively low (0.41). It was concluded that the CFSS-DS might be of clinical value as a screening device of dental fear, whereas its predictive value of fearful behavior should not be overestimated.     

Change in cognitive capabilities in the oldest old: the effects of proximity to death in genetically related individuals over a 6-year period

Change in cognitive abilities was assessed over a 6-year period in a sample of monozygotic and same-sex dizygotic twin pairs (N = 507 individuals), aged 80 and older (mean age = 83.3 years: SD = 3.1). who remained nondemented over the course of the study. Latent growth models (LGMs) show that chronological age and time to death are consistent predictors of decline in measures of memory, reasoning, speed, and verbal abilities. Multivariate LGM analysis resulted in weak and often negative correlations among rates of change between individuals within twin pairs, indicating greater differential change within twin pairs than occurs on average across twin pairs. These findings highlight several challenges for estimating genetic sources of variance in the context of compromised health and mortality-related change.     

Dependency and perfectionism: Short-term dynamic group psychotherapy for university students

Abstract

This paper is based on the authors' experiences of conducting short-term psychodynamic group therapy with university students. The therapy groups focus on common problems among the members, i.e. perfectionism, procrastination, and fear of graduation. Working on their dependency and on their inadequate separation from parental figures typically helps the students cope more creatively with their academic problems. The paper explores technical questions and possible advantages in working within a short time frame using a group analytic approach.     

Silence is golden? Characteristics and experiences of self-reported whistleblowers

This study investigates the characteristics of whistleblowers, the prevalence and nature of whistleblowing, and the occurrence of retaliation after whistleblowing using a randomly selected and representative sample of Norwegian employees. The results showed that 12 per cent self-reported as whistleblowers according to an operational definition. Being a leader, or a union or personnel safety representative was significantly related to whistleblowing. The most frequently reported wrongdoing was harassment conducted by a single colleague. Wrongdoer(s) received mixed responses, from no reaction to reprimand. Even though most whistleblowers were not sanctioned, they reported less job satisfaction and more workplace bullying than did nonwhistleblowers. Only a few were rewarded. For the most part, wrongdoing was stopped or reduced. However, whistleblowing was only partially effective, because whistleblowers reported lack of feedback about the result of their report. Results also showed that the status of the wrongdoer was related to the reaction he or she received afterwards, as were the type of wrongdoing and the effect on the wrongdoing, and the type of wrongdoing and the effect on the wrongdoer(s). Potential explanations for the results, such as the type of sample and power distance, are discussed. Practical implications of the study are also addressed, such as the importance of providing feedback to whistleblowers.     

Type 2 Diabetes Mellitus and Cognitive Performance in a Population-Based Sample of the Oldest Old: Impact of Comorbid Dementia

We examined the relationship between type 2 diabetes mellitus and cognitive function in a population-based sample of very old people. The sample comprised 338 persons, aged 80-93 years (mean age 83.5 years), of whom 70 persons had type 2 diabetes mellitus. Measures of cognitive functioning included tests of perceptual speed, visuo-spatial ability, inductive reasoning, short-term memory, semantic memory, episodic memory, and the Mini-Mental State Examination. Regression analyses showed that type 2 diabetes mellitus duration was related to test performance across all cognitive domains, with the exception of short-term memory, such that longer duration was associated with lower test performance. When cases with dementia were excluded from the sample, further analyses showed that diabetes duration was not associated with cognitive test performance. This indicates that diabetes is not related to lower cognitive function in the general population of non-demented old people. Diabetes, however, increases the risk for cerebrovascular incidents, like stroke, that may contribute to vascular dementia.