Childhood stress: Perceptions of children and professionals

An assessment instrument was developed to measure children's perceptions of stressors in their lives, as well as their experiences and emotional reactions to these stressors. Two approaches from the adult literature, major life events and daily hassles, were compared for children. In addition, a comparison between children's and professionals' ratings of the severity of various stressors was made, as well as an examination of the relationship of experience and self-reported reaction to children's ratings. Results indicate that children's ratings of the severity of stressors do differ from adults', particularly when children have experienced the stressor. Further investigation in the study of childhood stress incorporating children's perceptions is proposed.     

Effects of stress and retesting on role play tests of social skill

The purpose of this study was to examine the role of stress in performance on role play tests of social skill. Chronic psychiatric patients were tested in a formal videotape studio or in an informal consulting room setting. Motoric and physiological measures were secured. In addition, one-half of the subjects were retested one week later. In contrast to previous studies, results indicated that the assessment was not stressful. The two groups were not different on any measure, and the mean heart rates ranged from only 80 to 84 b.p.m. The effects of retesting were difficult to interpret. There were reductions in motoric indices of anxiety (speech disruptions) but not on physiological indices. Overall, testretest reliability was quite high. The results raise several questions which affect interpretation of many social skills studies in the literature.     

Multivariate stochastic processes compatible with “aspect” models of similarity and choice

Various recent works have developed feature or aspect models of similarity and preference. These models are more concerned with the fine detail of the judgment process than were prior models, but nevertheless they have not in general developed an underlying stochastic process compatible with the assumed structure. In this paper, we show that a particular class of multivariate stochastic processes, namely those associated with the Marshall-Olkin multivariate exponential distribution, generates several of these models. In particular, such stochastic processes (appropriately interpreted) yield Tversky's elimination by aspects model, Edgell and Geisler's (normal) additive random aspects model, and Shepard and Arabie's additive cluster model.This work was supported by Natural Science and Engineering Research Council of Canada Grant A8124 to A.A.J. Marley.     

Tests for stability in linear structural equation systems

Interpretations regarding the effects of exogenous and endogenous variables on endogenous variables in linear structural equation systems depend upon the convergence of a matrix power series. Convergence depends upon the eigenvalues of the structural coefficient matrix. The test for convergence developed by Jöreskog and Sörbom is shown to be only sufficient, not necessary and sufficient.     

A note on the investigation of local and global identifiability

In general, nonlinear models such as those commonly employed for the analysis of covariance structures, are not globally identifiable. Any investigation of local identifiability must either yield a mapping of identifiability onto the entire parameter space, which will rarely be feasible in any applications of interest, or confine itself to the neighbourhood of such points of special interest as the maximum likelihood point.The author would like to thank J. Jack McArdle and Colin Fraser for their comments on this paper.     

The use of latent class models for assessing prerequisite relations and transference among traits

This paper presents a strategy for pairwise assessment which may be used to evaluate the nature of both prerequisite and transference relations existing among a set of traits. This strategy is appropriate for use both within a confirmatory context, in which an attempt is made to establish the validity of some specified set of relations among traits, as well as within an exploratory context, in which a search is made for unconjectured prerequisite and transference relations existing between pairs of traits. Both uses of this strategy are based on a variety of latent class models which are representative of various possible relational states existing between pairs of traits. Thus, the nature of trait relations may be investigated through the use of statistical assessments of both absolute and relative fit attained by these models. An application is presented to exemplify how this strategy may be used within the exploratory context.The author is obliged to Clifford Clogg, C. Mitchell, Dayton, and William Schafer for helpful comments made regarding a previous draft of this paper as well as to Mary Papageorgiou who provided access to the data which was considered in this study.     

On Herrnstein's equation and related forms

In 1970, Herrnstein proposed a simple equation to describe the relation between response and reinforcement rates on interval schedules. Its empirical basis is firm, but its theoretical foundation is still uncertain. Two approaches to the derivation of Herrnstein's equation are discussed. It can be derived as the equilibrium solution to a process model equivalent to familiar linear-operator learning models. Modifications of this approach yield competing power-function formulations. The equation can also be derived from the assumption that response strength is proportional to reinforcement rate, given that there is a ceiling on response rate. The proportional relation can, in turn, be derived from a threshold assumption equivalent to Shimp's “momentary maximizing”. This derivation implies that the two parameters of Herrnstein's equation should be correlated, and may explain its special utility in application to internal schedules.     

Transformation of a three-mode multidimensional scaling solution to indscal form

Relations between Tucker's three-mode multidimensional scaling and Carroll and Chang's INDSCAL are discussed. The possibility is raised that it may be profitable to attempt to transform a three-mode solution to the general form of an INDSCAL solution. Operationally, this involves transforming the three-mode core matrix so that each section is, as nearly as possible, a diagonal matrix. A technique is developed for accomplishing such a transformation, and is applied to two sets of data from the literature. Results indicate that the process is both feasible and valuable, providing useful information on the relative appropriateness of the two models.     

How a high working memory capacity can increase proactive interference

Previous findings suggested that a high working memory capacity (WMC) is potentially associated with a higher susceptibility to proactive interference (PI) if the latter is measured under high cognitive load. To explain such a finding, we propose to consider susceptibility to PI as a net effect of individual executive processes and the intrinsic potential for PI. With the latter, we refer to the amount of information that is activated at a given time and that has the potential to exert PI subsequently. In two studies deploying generalized linear mixed models, susceptibility to PI was modeled as the decline of performance over trials of a complex span task. The results revealed that a higher WMC was associated with a higher susceptibility to PI. Moreover, the number of stimuli recalled in one trial as a proxy variable for the intrinsic potential for PI negatively affected memory performance in the subsequent trial.     

Are Individuals Always Aware of Their Trauma-Related Intrusive Thoughts? A Study of Meta-Awareness

Individuals are not always aware of their mental content. We tested whether lack of awareness occurs in those who have experienced trauma, with and without posttraumatic stress disorder (PTSD). We also examined the role of proposed cognitive mechanisms (working memory and inhibition) in explaining unnoticed intrusions. Individuals with PTSD (n = 44), and varying levels of symptoms (high posttraumatic stress [PTS]: n = 24; low PTS: n = 37) reported on intrusive thoughts throughout a reading task. Intermittently, participants responded to probes about whether their thoughts were trauma related. Participants were “caught” engaging in unreported trauma-related thoughts (unnoticed intrusions) for between 24 and 27% of the probes in the PTSD and high PTS groups, compared with 15% of occasions in the low PTS group. For trauma-related intrusions only, participants lacked meta-awareness for almost 40% of probes in the PTSD group, which was significantly less than that observed in the other groups (～60%). Contrary to predictions, working memory and response inhibition did not predict unnoticed intrusions. The results suggest that individuals who have experienced significant trauma can lack awareness about the frequency of their trauma-related thoughts. Further research is warranted to identify the mechanisms underpinning the occurrence of unnoticed intrusions.