Some additional results on principal components analysis of three-mode data by means of alternating least squares algorithms

Kroonenberg and de Leeuw (1980) have developed an alternating least-squares method TUCKALS-3 as a solution for Tucker's three-way principal components model. The present paper offers some additional features of their method. Starting from a reanalysis of Tucker's problem in terms of a rank-constrained regression problem, it is shown that the fitted sum of squares in TUCKALS-3 can be partitioned according to elements of each mode of the three-way data matrix. An upper bound to the total fitted sum of squares is derived. Finally, a special case of TUCKALS-3 is related to the Carroll/Harshman CANDECOMP/PARAFAC model.     

Learning from exemplars: emulation,character formation and the complexities of ordinary life

In the field of character education role-modelling is advocated as an important pedagogical strategy. It is supposed that students learn from ‘significant others’ who exemplify important virtues and values. However, in these strategies it is not clear what and how students precisely can and should learn from exemplars and how the following of exemplars relates to the educational aim of ‘becoming a self.’ In this article, it is argued that modelling is only a relevant pedagogical strategy if moral exemplars are somehow related to life in its full extent, including its moral complexities and ambiguities. Understanding moral exemplarity demands not only the reappropriation of an Aristotelian conception of emulation but also an understanding of the typical modern relocation of moral exemplarity in the fullness of life, importantly originating from what Charles Taylor calls the Protestant ‘affirmation of ordinary life.’ In addition, a distinction is introduced between ‘role exemplarity’ and ‘existential exemplarity.’ Based on this distinction it is argued that emulation should not be limited to learning from role models, but should also include something that runs deeper, to the depth of our own subjectivity or self.     

Concurrent Cortical Representations of Function- and Size-Related Object Affordances: An fMRI Study

Previous work has shown that the perception of a graspable object may automatically potentiate actions that are tailored to specific action-related features of the object (e.g., its size) and may be related to its immediate grasping as well as to its long-term, functional use. We investigated the neural correlates of function- and size-related object affordances that may be concurrently potentiated by a graspable object. Participants were lying in a MR scanner holding a large switch in one hand and a small switch in the other hand. They passively attended a large or a small object with clearly separated functional and graspable end that was displayed centrally at an average angle of 45 degrees. Participants responded to the direction of an arrow that was overlaid on the object after a mean period of 1,000 ms after object onset and was pointing to the left or to the right with equal probability. Response times were shorter when the arrow pointed to the functional end of the object and when the responses were made with the switch that was congruent to the size of the perceived object. A clear distinction was found in the representation of function- and size-related affordances; the former was represented in the posterior parietal cortex and the latter in prefrontal, premotor, and primary sensorimotor cortices. We conclude that different aspects of object-directed actions may be automatically potentiated by individual object features and are represented in distinct brain areas.     

Incremental grouping of image elements in vision

One important task for the visual system is to group image elements that belong to an object and to segregate them from other objects and the background. We here present an incremental grouping theory (IGT) that addresses the role of object-based attention in perceptual grouping at a psychological level and, at the same time, outlines the mechanisms for grouping at the neurophysiological level. The IGT proposes that there are two processes for perceptual grouping. The first process is base grouping and relies on neurons that are tuned to feature conjunctions. Base grouping is fast and occurs in parallel across the visual scene, but not all possible feature conjunctions can be coded as base groupings. If there are no neurons tuned to the relevant feature conjunctions, a second process called incremental grouping comes into play. Incremental grouping is a time-consuming and capacity-limited process that requires the gradual spread of enhanced neuronal activity across the representation of an object in the visual cortex. The spread of enhanced neuronal activity corresponds to the labeling of image elements with object-based attention.     

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.     

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.