Optical magnification as event information

Summary The geometrical optics of approach events is delineated. It is shown that optical magnification provides information about distance and time until collision. An experiment is described in which two objects - white styropor® spheres 10 cm in diameter, seen against a white plaster wall - were moved simultaneously at equal, constant speed along straight, converging paths at eye level towards a human observer and towards a common, virtual point of collision which either coincided with the observer's station point or was placed in front of, or behind, that point. Approach events differed with regard to trajectories, distances, velocities, and times-to-collision involved. Events were observed monocularly fixating and binocularly non-fixating, without head movements. The objects always stopped before colliding, and subjects had to respond to the virtual collisions. Most responses were too early, especially for impending collisions at, or behind the observers' station point. Responses for impending collisions in front of the observers tended to be too late, especially for larger total amounts of optical magnification and higher velocities, which together imply shorter times-to-collision. Relative errors were comparatively larger for very short and very long times-to-collision throughout, where events of the first kind were overshot, the latter ones undershot. Results are interpreted with reference to biological theories and the constraints imposed by geometrical optics. Special attention is focused on the issue of unavoidable, necessary confounding of variables in time-to-collision studies.     

Measures of national stereotypes as predictors of the latencies of inductive versus deductive stereotypic judgements

According to Taifel's accentuation theory, national stereotypes can be thought of as the correlation between trait dimensions and national affiliations, This correlation is high when the trait shows high homogeneity within and high distinctiveness between the national groups. The present study tested the hypothesis that a trait's distinctiveness would facilitate inductive stereotypic judgements (inferences from trait to nationality) whereas homogeneity would facilitate deductive stereotypic judgements (inferences from nationality to trait). The latencies of inductive and deductive stereotypic judgements of 48 German subjects were assessed for 39 traits and three foreign nationalities (English, French, Italian). Multiple regression analyses using latencies for both types of judgements us criterion variables and both distinctiveness and homogeneity as predictor variables were conducted. The stereotype measures of Katz and Braly and McCauley and Stitt served as additional predictor variables. As expected from accentuation theory, distinctiveness predicted inductive but not deductive latencies, whereas homogeneity predicted deductive but not inductive latencies. For the latencies of deductive stereotypic judgements, the stereotype measure of Katz and Braly as well as that of McCauley and Stitt also proved to be significant predictors. The results are discussed and recommendations are given with respect to the assessment of national stereotypes.     

Coincidence of attention deficit disorder and atopic disorders in children: Empirical findings and hypothetical background

ADDH children are often reported to display signs of allergies to various substances and/or atopic (AT) symptoms (i.e., atopic eczema, hay fever, or asthma). Since, at least for a subgroup of these children, a common biological background for both ADD and atopy may be assumed that may involve brain catecholamines, our hypothesis was that in a group of AT children (mainly atopic eczema) signs of ADD should appear more often than in controls. Parental hyperactivity ratings revealed a significantly higher frequency of ADD symptoms in the AT group, and laboratory tests sensitive to attentional capacity and inhibitory functions showed poorer performance in the AT children, the findings being similar to those reported in hyperactives. Thus, our results add support to the assumption of a common predisposing factor for both AT and ADDH in a subgroup of children.     

The voice of confidence: Paralinguistic cues and audience evaluation

A standard speaker read linguistically confident and doubtful texts in a confident or doubtful voice. A computer-based acoustic analysis of the four tapes showed that paralinguistic confidence was expressed by increased loudness of voice, rapid rate of speech, and infrequent, short pauses. Under some conditions, higher pitch levels and greater pitch and energy fluctuations in the voice were related to paralinguistic confidence. In a 2 × 2 design, observers perceived and used these cues to attribute confidence and related personality traits to the speaker. Both text and voice cues are related to confidence ratings; in addition, the two types of cue are related to differing personality attributes.     

Symmetrie und Symmetriebrechung

In spite of their growing specialization, modern natural sciences intend to reduce their theories to some fundamental structures: Physics tries to unify the different physical forces in one fundamental force. Chemistry tries to explain the structure of chemical substances by the quantum mechanics of molecules. Biology tries to reduce the processes of life to biochemical and biophysical laws. Mathematically, the unification of natural science can be described by structures of symmetry, the specialization of science, the variety, and emergence of new phenomena by symmetry breaking. In the following, the successes and lacks of the reductionistic program are shown in recent developments of physics, chemistry, and biology. Philosophical discussions on holism, reductionism, and unification of science can be clarified by structures of symmetry and symmetry breaking. Alternative non-reductionistic view-points are not only possible, but desirable for the lacks in the reductionistic program. Nevertheless, the categorical framework of symmetry and symmetry breaking supports interdisciplinary work and gives new insight in a common structure and theory of natural science.     

Brain dopamine and kinematics of graphomotor functions

Three experiments were performed in an attempt to achieve a better understanding of the effect of dopamine on handwriting. In the first experiment, kinematic aspects of handwriting movements were compared between healthy participants and patients with Parkinson's disease (PD) on their usual dopaminergic treatment and following withdrawal of dopaminergic medication. In the second experiment, the writing performance of healthy participants with a hyperechogenicity of the substantia nigra as detected by transcranial sonography (TCS) was compared with the performance of healthy participants with low echogenicity of the substantia nigra. The third experiment examined the effect of central dopamine reduction on kinematic aspects of handwriting movements in healthy adults using acute phenylalanine and tyrosine depletion (APTD). A digitising tablet was used for the assessment of handwriting movements. Participants were asked to perform a simple writing task. Movement time, distance, velocity, acceleration and measures of fluency of handwriting movements were measured. The kinematic analysis of handwriting movements revealed that alterations of central dopaminergic neurotransmission adversely affect movement execution during handwriting. In comparison to the automatic processing of handwriting movements displayed by control participants, participants with an altered dopaminergic neurotransmission shifted from an automatic to a controlled processing of movement execution. Central dopamine appears to be of particular importance with regard to the automatic execution of well-learned movements.