University of Amsterdam

About: University of Amsterdam is a education organization based out in Amsterdam, Noord-Holland, Netherlands. It is known for research contribution in the topics: Population & Context (language use). The organization has 59309 authors who have published 140894 publications receiving 5984137 citations. The organization is also known as: UvA & Universiteit van Amsterdam.

The concept of validity

Abstract: This article advances a simple conception of test validity: A test is valid for measuring an attribute if (a) the attribute exists and (b) variations in the attribute causally produce variation in the measurement outcomes. This conception is shown to diverge from current validity theory in several respects. In particular, the emphasis in the proposed conception is on ontology, reference, and causality, whereas current validity theory focuses on epistemology, meaning, and correlation. It is argued that the proposed conception is not only simpler but also theoretically superior to the position taken in the existing literature. Further, it has clear theoretical and practical implications for validation research. Most important, validation research must not be directed at the relation between the measured attribute and other attributes but at the processes that convey the effect of the measured attribute on the test scores.

Analysis of shared heritability in common disorders of the brain

Abstract: Disorders of the brain can exhibit considerable epidemiological comorbidity and often share symptoms, provoking debate about their etiologic overlap. We quantified the genetic sharing of 25 brain disorders from genome-wide association studies of 265,218 patients and 784,643 control participants and assessed their relationship to 17 phenotypes from 1,191,588 individuals. Psychiatric disorders share common variant risk, whereas neurological disorders appear more distinct from one another and from the psychiatric disorders. We also identified significant sharing between disorders and a number of brain phenotypes, including cognitive measures. Further, we conducted simulations to explore how statistical power, diagnostic misclassification, and phenotypic heterogeneity affect genetic correlations. These results highlight the importance of common genetic variation as a risk factor for brain disorders and the value of heritability-based methods in understanding their etiology.

Self-categorisation, commitment to the group and group self-esteem as related but distinct aspects of social identity

Abstract: The aim of this study is to show that, when examining social identification, it is both possible and important to distinguish between self-categorisation, commitment to the group, and group self-esteem, as related but separate aspects of group members' social identity. This was demonstrated in an experiment (N=119), in which Ingroup Status (high/low), Ingroup Size (majority/minority), and Group Formation (self-selected/assigned group membership) were manipulated orthogonally. The results of this study confirm that these three aspects of social identity can be distinguished as separate factors in a principal components analysis. Furthermore, as predicted, the three aspects are differentially related to manipulated group features, as well as displays of ingroup favouritism. Group members' self-categorisations were only affected by the relative size of the group, while group self-esteem was only influenced by group status. Affective commitment to the group depended both on group status and on the group assignment criterion. Importantly, only the group commitment aspect of social identity mediated displays of ingroup favouritism. Copyright © 1999 John Wiley & Sons, Ltd.