A loss function for alpha factor analysis

Most of the factor solutions can be got by minimizing a corresponding loss function. However, up to now, a loss function for the alpha factor analysis (AFA) has not been known. The present paper establishes such a loss function for the AFA. Some analogies to the maximum likelihood factor analysis are discussed.The author is greatly indebted to Prof. Henry F. Kaiser (University of California, Berkeley) for his kind encouragement. He is also indebted to an anonymous referee ofPsychometrika for having confronted him with the problem in 1977. Financial support by the Wiener Hochschuljubiläumsstiftung is gratefully acknowledged.     

Eine neue Wahrnehmungstäuschung

Zusammenfassung Die Grenze des durch beide Arme bestimmten menschlichen Doppelgreifraumes hat die Gestalt einer Kugeldoppelhaube. Alle Punkte dieser Grenzfläche sind durch Greifbewegung gleich bequem (noch) erreichbar, wobei der Doppelarm als einheitliches Greif organ aufzufassen ist. Es besteht für diese Fläche nach allen Richtungen Gleichheit der Greifentfernung. Durch Spiegel-Hand-Versuche kann man nunmehr zeigen, daß alle Punkte dieser Grenzfläche bei visueller Wahrnehmung auch vom Auge aus gleichweit entfernt erscheinen, obwohl dies geometrisch schon wegen der exzentrischen Lage des Auges keineswegs der Fall ist. Die Grenze des Doppelgreifraumes nimmt beim Aufbau des menschlichen Sehraumes eine Schlüsselstellung ein.Man kann an dem beschriebenen Phänomen mit Aussicht auf Erfolg neue psychische Grundgesetze aufspüren. Versuche mit sogenannten Contergankindern können hierzu neue Aufschlüsse liefern.

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Summary The periphery delimiting the space circumscribed by the motional range of both human arms takes the shape of a double truncated sphere. All points of this periphery may still be reached with equal ease by a mere gripping motion (regarding, for the purposes of this study, the two arms as a single prehensile organ), and peripheral equidistance of reach exists in all directions. By means of tests in which the outstretched hand is expediently reflected in a mirror it can now be demonstrated that in visual perception (due to the above-mentioned motional equidistance) the entire double-spherical periphery appears equidistant also from the vantage-point of the eye, even though geometrically this is by no means the case. The periphery of the bilateral space of prehension, therefore, assumes a key position in the configuration of space as perceived by the human eye.The phenomenon opens views fowards new basic psychic laws. Also experiments with thalidomide children may provide new insights.

     

On the existence and uniqueness of maximum-likelihood estimates in the Rasch model

Necessary and sufficient conditions for the existence and uniqueness of a solution of the so-called unconditional (UML) and the conditional (CML) maximum-likelihood estimation equations in the dichotomous Rasch model are given. The basic critical condition is essentially the same for UML and CML estimation. For complete data matricesA, it is formulated both as a structural property ofA and in terms of the sufficient marginal sums. In case of incomplete data, the condition is equivalent to complete connectedness of a certain directed graph. It is shown how to apply the results in practical uses of the Rasch model.Paper read at the European Meeting of the Psychometric Society, Groningen, June 19–21, 1980.Part of the research reported herein was done while the author was staying at the Pulmologisches Zentrum der Stadt Wien; he is indebted to Professor Dr. F. Muhar and Dr. R. Mutschlechner for providing excellent working conditions.     

Nondirectiveness and genetic counseling

Nondirectiveness is the generally required and professed standard for genetic counseling. However, studies are lacking in the field of human genetics and in other disciplines which address either the theory or practice of this type of therapeutic procedure in the context of genetic counseling. Moreover, there is no indication the further development this concept has undergone in client-centered therapy has been acknowledged in human genetics. This could be due tot he historical development of genetic counseling, its inherent conflicts and often undefined goals, and the latent need of human geneticists to defend themselves against being accused of eugenic tendencies. Nondirectiveness and directiveness, however, can neither adequately describe what takes place in genetic counseling, nor can they — according to their original meaning — be used to define an ethical standard of genetic counseling. Starting with the writings by Carl Rogers (1942), an experiential approach is described, in which counseling is seen as a process of influence, which is wished by all the persons involved, during which activities are oriented toward the experience of the client, and which allows the counselor to communicate openly and directly with the client. The present study illustrates the use of the experiential approach in genetic counseling and shows that it can uphold the principle of ethics, which nondirectiveness demands and, at the same time, prevent the inevitable and unresolvable contradictions. This means that in their training genetic counselors must learn to recognize and constantly reflect on the influence they can and want to exert. In order to be able to use this influence in a responsible manner, genetic counselors must also learn to have a certain degree of flexibility so that they are able to check at any time how their client responds to this influence.     

A Bayesian approach to nonlinear latent variable models using the Gibbs sampler and the metropolis-hastings algorithm

Nonlinear latent variable models are specified that include quadratic forms and interactions of latent regressor variables as special cases. To estimate the parameters, the models are put in a Bayesian framework with conjugate priors for the parameters. The posterior distributions of the parameters and the latent variables are estimated using Markov chain Monte Carlo methods such as the Gibbs sampler and the Metropolis-Hastings algorithm. The proposed estimation methods are illustrated by two simulation studies and by the estimation of a non-linear model for the dependence of performance on task complexity and goal specificity using empirical data.     

Kognitive Lernermodellierung

Different types of learner models and their usefulness for tutoring have been discussed widely since the beginning of intelligent tutoring systems. In this paper we compare pragmatic and cognitive approaches of learner modeling. Pragmatic approaches consider relevant learner features for adaptive methods in learning environments and adapt different aspects of instruction to a restricted model representing these features. Cognitive approaches aim for a psychologically adequate modeling of human problem solving. We introduce the case-based learner model ELM as an example of a cognitive approach to learner modeling. The learning environments ELM-PE and ELM-ART use ELM for adaptional methods on conceptual, plan, and episodic levels and provide individual help and learning support. Especially in the case of integrated learning environments like ELM-ART which support a variety of learning activities, a combination of pragmatic and cognitive learner models is proposed to be a necessary and useful solution.     

Stroop facilitation in tinnitus patients: an experiment conducted via the world wide web.

Cognitive mechanisms have been proposed to play an important role in tinnitus. In the present study, tinnitus participants were administered an emotional Stroop test via the Internet, incorporating words related to tinnitus concerns. In line with previous research using this Web-based version of the emotional Stroop test, faster color naming was demonstrated for concern-relevant words relative to neutral words. The present results thus provided support for a role for cognitive factors that are important for the understanding of tinnitus. However, future research is warranted in order to clarify the precise mechanisms involved in tinnitusrelated Stroop effects.