Anchor Point Selection: Scale Alignment Based on an Inequality Criterion

For detecting differential item functioning (DIF) between two or more groups of test takers in the Rasch model, their item parameters need to be placed on the same scale. Typically this is done by means of choosing a set of so-called anchor items based on statistical tests or heuristics. Here the authors suggest an alternative strategy: By means of an inequality criterion from economics, the Gini Index, the item parameters are shifted to an optimal position where the item parameter estimates of the groups best overlap. Several toy examples, extensive simulation studies, and two empirical application examples are presented to illustrate the properties of the Gini Index as an anchor point selection criterion and compare its properties to those of the criterion used in the alignment approach of Asparouhov and Muthén. In particular, the authors show that—in addition to the globally optimal position for the anchor point—the criterion plot contains valuable additional information and may help discover unaccounted DIF-inducing multidimensionality. They further provide mathematical results that enable an efficient sparse grid optimization and make it feasible to extend the approach, for example, to multiple group scenarios.     

Toward Common Ground: Catholicism and Pentecostalism in African Christianity

After reviewing the great appeal of Pentecostal/charismatic spirituality as a religious phenomenon that has come to stay on the tapestry of the pastoral ecology of African Christianity, this article suggests a more dynamic and practical interface and collaboration with these movements by the Catholic Church in Africa, using the Vatican Council's embrace of ecumenism and dialogue.     

Jung's twin brother. Otto Gross and Carl Gustav Jung

This paper is a preliminary communication of several years of research into the life and work of the Austrian psychoanalyst and anarchist Otto Gross (1877–1920). Although he played a pivotal role in the birth of modernity, acting as a significant influence upon psychiatry, psychoanalysis, ethics, sociology and literature, he has remained virtually unknown to this day. Following a biographical sketch and an overview of his main theoretical contributions, the impact of Gross' life and work on the development of analytical theory and practice is described. His relationship with some of the key figures in psychoanalysis is presented, with particular emphasis on his connections to Jung. The paper concludes with an account of relevant contemporary interest in his work: the founding of the International Otto Gross Society, the first edition of The Collected Works of Otto Gross on the Internet, and the 1st and 2nd International Otto Gross Congresses which took place in Berlin in 1999 and at the Burghölzli Clinic, Zürich, in October 2000.     

Demonstrations of a generation effect in context memory

Generation often leads to increased memorability within a laboratory context (see, e.g., Slamecka & Graf, 1978). Of interest in the present study is whether the benefits of generation extend beyond item memory to context memory. To investigate this question, in three experiments, we asked subjects to remember in which of two contexts they had read or generated words. In Experiment 1, the contexts were two different rooms; in Experiment 2A, the contexts were two different computer screens; in Experiment 2B, the contexts were different perceptual characteristics of the to-be-remembered words. In all experiments, subjects were better at remembering the context of generated words than of read words.     

Spatial reconstruction of human motion by means of a single camera and a biomechanical model

The value of the results of the inverse dynamic analysis procedures used in the study of human tasks is dependent on the quality of the kinematic and kinetic data supplied to the biomechanical model that supports it. The kinematic data, containing the position, velocity and acceleration of all anatomical segments of the biomechanical model, result from the reconstruction of human spatial motion by means of the evaluation of the anatomic points positions that enable to uniquely define the position of all anatomical segments. Furthermore, the motion data must be kinematically consistent with the structure of the biomechanical model used in the analysis. The traditional photogrammetric methodologies used for the spatial reconstruction of the human motion require images of two or more calibrated and synchronized cameras. This is due to the fact that the projection of each anatomical point is described by two linear equations relating its three spatial coordinates with the two coordinates of the projected point. The need for the image of another camera arises from the fact that a third equation is necessary to find the original spatial position of the anatomical point. The methodology proposed here substitutes the projection equations of the second camera with the kinematic constraint equations associated with a biomechanical model in the motion reconstruction process. In the formulation the system of equations arising from the point projections and biomechanical model kinematic constraints, representing the constant length of the anatomical segments, are solved simultaneously. Because the system of equations has multiple solutions for each image, a strategy based on the minimization of a cost function associated to the smoothness of the reconstructed motion is devised. It is shown how the process is implemented computationally avoiding any operator intervention during the motion reconstruction for a given time period. This leads to an automated computer procedure that ensures the uniqueness of the reconstructed motion. The result of the reconstruction process is a set of data that is kinematically consistent with the biomechanical model used. Through applications of the proposed methodology to several sports exercises its benefits and shortcomings are discussed.     

Social Influence Dynamics in Aptitude Tasks

Learning and, more generally, the development of cognitive processes in children has been thought to depend on the nature of the conflict induced by confrontation with others (i.e., socio-cognitive conflict). The aim of this article is to extend this notion to social-influence situations involving adolescents and young adults through the presentation of a model that explains social influence in aptitude tasks. This model takes into account the differences or similarities of the competencies of the source and target. It conceptualizes the social versus epistemic regulations of conflict in terms of an identity threat that can be induced by social comparison. To illustrate parts of the model, several experiments are briefly summarized. One demonstrates the conflict regulation dynamics involved in the similarities or differences of the sources' and targets' competencies, while the others show how social-influence dynamics are modified by the presence or absence of a threat to self-competence. This revised version was published online in August 2006 with corrections to the Cover Date.     

Acquired equivalences between auditory stimuli in dolphins (Tursiops truncatus)

This study investigated whether dolphins would show evidence of equivalence class formation between auditory stimuli. Bottlenose dolphins were trained to press one or other of two response levers depending on which one of four auditory stimuli had been previously presented. Once they had learned the initial discriminations, the stimulus-lever contingencies was repeatedly reversed. Within any given session, however, pressing of one lever always led to reward with one set of two tones and pressing the other lever led to non-reward with an alternative set of two tones. After sufficient experience with this response reversal procedure, the dolphins spontaneously chose the same levers they had first learned to be correct with one of the across-set stimulus pairs when later in the session they were presented with the other of the across-set stimulus pairs. They thus demonstrated that they had associated the tones belonging to the two sets within two separate functional classes. It is discussed why the dolphins succeeded with auditory stimuli when they had previously failed in a similar task with visual stimuli. Received: 7 December 1999 / Accepted after revision: 23 June 2000