Contents of Volume 14

Volume Contents

Contents of Volume 14     

The locus of adaptation to altered gain in aimed movements

Altered gain settings cause a mismatch between the actual movement amplitude across the surface and the distance covered on a real time visual display. The present study pursued three objectives of how adaptation to altered gain affects aimed motor behavior. First, we replicated findings of an earlier study reporting a negative linear relation between gain and both target acquisition time and end-point variability. This means that our data do not agree with the classic U-shaped relation between gain and acquisition time. Second, our results proved to be robust when we manipulated movement difficulty by varying target distance. And third, dividing a movement into four successive sections on the basis of key kinematic events revealed the locus of the adaptation to altered gain within movement execution. Time differences between gain conditions proved to start at a very early part of the movement, but appeared to be absent in the final movement section. In contrast, differences between gain conditions regarding the use of online feedback were also present in the last part of the movement during which the final target approach takes place.     

Phonological and morphological consistency in the acquisition of vowel duration spelling in Dutch and German

In Dutch, vowel duration spelling is phonologically consistent but morphologically inconsistent (e.g., paar-paren). In German, it is phonologically inconsistent but morphologically consistent (e.g., Paar-Paare). Contrasting the two orthographies allowed us to examine the role of phonological and morphological consistency in the acquisition of the same orthographic feature. Dutch and German children in Grades 2 to 4 spelled singular and plural word forms and in a second task identified the correct spelling of singular and plural forms of the same nonword. Dutch children were better in word spelling, but German children outperformed the Dutch children in nonword selection. Also, whereas German children performed on a similar level for singular and plural items, Dutch children showed a large discrepancy. The results indicate that children use phonological and morphological rules from an early age but that the developmental balance between the two sources of information is constrained by the specific orthography.     

A gradual spread of attention during mental curve tracing

The visual system has to segregate objects that are relevant to behavior from other objects and the background, if they are embedded in a visual scene. This segregation process can be time consuming, especially if the relevant object is spatially extended and overlaps with other image components, but the cause of the delays is presently not well understood. In the present study, we used a curve-tracing task to investigate processing delays during the grouping of contour segments into elongated curves. Our results indicate that contour segments that need to be grouped together are labeled with visual attention. Attention gradually spreads from contour segments that were labeled previously to other contours that are colinear and connected to them. The contour-grouping task is completed as soon as attention is directed to the entire curve. We conclude that processing delays during contour grouping are caused by a time-consuming spread of visual attention.     

Developmental dyslexia and discrimination in speech perception: a dynamic model study

At the behavioral level one of the primary disturbances involved in congenital dyslexia concerns phonological processing. At the neuroarchitectural level autopsies have revealed ectopies, e.g., a reduced number of neurons in the upper layers of the cortex and an increased number in the lower ones. In dynamic models of interacting neuronal populations the behavioral level can be related to the neurophysiological level. In this study an attempt is made to do so at the cortical level. The first focus of this model study are the results of a Finnish experiment assessing geminate stop perception in quasi speech stimuli by 6 month old infants using a head turning paradigm and evoked potentials. The second focus of this study are the results of a Dutch experiment assessing discrimination of transients in speech stimuli, by adult dyslexics and controls and 2 month old infants. There appears to be a difference in the phonemic perceptual boundaries of children at genetic risk for dyslexia and control children as revealed in the Finnish study. Assuming a lowered neuronal density in the 'dyslexic' model, reflecting ectopies, it may be postulated that less neuronal surface is available for synaptic connections resulting in a lowered synaptic density and thus a lowered amount of available neurotransmitter. A lowered synaptic density also implies a reduced amount of membrane surface available for neurotransmitter metabolism. By assuming both, a reduced upper bound of neurotransmitter and a reduced metabolic transmitter rate in the dynamic model, the Finnish experimental results can be approximated closely. This applies both to data from behavioral head turning and that of the evoked potential study. In the Dutch study adult dyslexics show poor performance in discriminating transients in the speech signal compared to the controls. The same stimuli were used in a a study comparing infants from dyslexic families and controls. Using the same transmitter parameters as in modeling the results of the Finnish study, also in this case the experimental results for adults and infants can be approximated closely. Simulation of behavioral and pharmaceutical interventions with the model provide predictions which can be put to the test in experiments.     

The assignment of scores for output‐based research funding

This paper considers the assignment of scores to research output items, such as articles, books, contributions to conference proceedings, doctoral dissertations, etc., under four distribution criteria: the advancement of pure and applied scientific research, the advancement of innovative problem solving, the dissemination of scientific knowledge, and the coverage of the cost of the research. These scores are to be used in the allocation of research funds to the faculties of a university. The present paper describes the experiments carried out within the framework of the Decision Analysis and Support Project of the International Institute of Applied Systems Analysis, Laxenburg, Austria. It summarizes the vivid discussions triggered by the experiment, and it also presents the results of an additional experiment. Copyright © 1999 John Wiley & Sons, Ltd.     

The effect of items in working memory on the deployment of attention and the eyes during visual search

Paying attention to an object facilitates its storage in working memory. The authors investigate whether the opposite is also true: whether items in working memory influence the deployment of attention. Participants performed a search for a prespecified target while they held another item in working memory. In some trials this memory item was present in the search display as a distractor. Such a distractor has no effect on search time if the search target is in the display. In that case, the item in working memory is unlikely to be selected as a target for an eye movement, and if the eyes do land on it, fixation duration is short. In the absence of the target, however, there is a small but significant effect of the memory item on search time. The authors conclude that the target for visual search has a special status in working memory that allows it to guide attention. Guidance of attention by other items in working memory is much weaker and can be observed only if the search target is not present in the display.     

Sound improves diminished visual temporal sensitivity in schizophrenia

Visual temporal processing and multisensory integration (MSI) of sound and vision were examined in individuals with schizophrenia using a visual temporal order judgment (TOJ) task. Compared to a non-psychiatric control group, persons with schizophrenia were less sensitive judging the temporal order of two successively presented visual stimuli. However, their sensitivity to visual temporal order improved as in the control group when two accessory sounds were added (temporal ventriloquism). These findings indicate that individuals with schizophrenia have diminished sensitivity to visual temporal order, but no deficits in the integration of low-level auditory and visual information.     

Under the Spell of the Ring

Among orthodox reformed Christians in the Netherlands fierce debates have occurred on moral aspects of Christian life. This essay discusses three major controversial moral issues that are related to conceptions of sex, gender, and sexuality: divorce/remarriage, women’s ordination, and homosexuality. By analysing several contributions to debates on these issues, it proposes and explores a hypothesis that concerns the role of a particular understanding of marriage as characterized by a hermeneutical construct: a communal, deeply rooted and subconscious normative principle that drives our interpretations of texts and practices. This essay illustrates the problems of both the dominance of marriage within Christian communities and lived faith, as well as the modern, romantic aspects of this particular understanding of marriage.     

An Experimental Investigation of Election Promises

We analyze the effect of election promises on electoral behavior in a laboratory experiment. In the experiment, politicians can make nonbinding election promises about how to split an endowment between themselves and the group. We find that promises affect both voting and voter beliefs about how much the politician will contribute to the public fund. The relationship is inverted U‐shaped with decreasing credibility of higher promises. Contributions of politicians are correlated with their promises in a similar pattern. The election promises are generally credible unless particularly high. Politicians keep promises more often if a reelection is possible and if the politician came into power by vote rather than by random draw. Voters reward high contributions in the previous period and punish promise breaking even after controlling for the contribution in the previous period or voters' beliefs about future contributions. By controlling for voters' beliefs, we distinguish retrospective from prospective voting. Our results suggest that voters both use promises for prospective voting and retrospectively punish broken promises.