The MBR metric

P. H. Schönemann's (1982, Bulletin of the Psychonomic Society, 19, 317–319; 1983, Journal of Mathematical Psychology, 27, 311–324) MBR metric is designed to account for distortion effects in distance estimates caused by upper bounds in the response scales. To test the MBR hypothesis, given data have to be transformed first into the half-open interval [0, 1). This is achieved by defining the greatest distance estimate as the upper bound, and then dividing all values by this bound plus some “small constant” e, which ensures that the interval is open. How e should be picked is left open. It is shown here that very small differences in the value chosen for e have massive effects on the fit of the MBR model. Moreover, if e → 0, then the fit will eventually get bad for all realistic data.     

The formation of rhythmic categories and metric priming

Two experiments on categorical rhythm perception are reported, the object of which was to investigate how listeners perceive discrete rhythmic categories while listening to rhythms performed on a continuous time scale. This is studied by considering the space of all temporal patterns (all possible rhythms made up of three intervals) and how they, in perception, are partitioned into categories, ie where the boundaries of these categories are located. This process of categorisation is formalised as the mapping from the continuous space of a series of time intervals to a discrete, symbolic domain of integer-ratio sequences. The methodological framework uses concepts from mathematics and psychology (eg convexity and entropy) that allow precise characterisations of the empirical results. In the first experiment, twenty-nine participants performed an identification task with 66 rhythmic stimuli (a systematic sampling of the performance space). The results show that listeners do not just perceive the time intervals between onsets of sounds as placed in a homogeneous continuum. Instead, they can reliably identify rhythmic categories, as a chronotopic time clumping map reveals. In a second experiment, the effect of metric priming was studied by presenting the same stimuli but preceded with a duple or triple metre subdivision. It is shown that presenting patterns in the context of a metre has a large effect on rhythmic categorisation: the presence of a specific musical metre primes the perception of specific rhythmic patterns.     

The priming of face recognition after metric transformations

Four experiments were performed to test whether the perceptual priming of face recognition would show invariance to changes in size, position, reflectional orientation (mirror reversal), and picture-plane rotation. In all experiments, subjects recognized faces in two blocks of trials; in the second block, some of the faces were identical to those in the first, and others had undergone metric transformations. The results show that subjects were equally fast to recognize faces whether or not the faces had changed in size, position, or reflectional orientation between the first and second presentations of the faces. In contrast, subjects were slower to recognize both faces and objects when they were planar-rotated between the first and second presentations. The results suggest that the same metric invariances are shown by both face recognition and basic-level object recognition.     

Modelling group decision making: Some important aspects for system design

Abstract

The discussion on work flexibility in organizations seems to be promising in terms of self-determination and autonomy of the concerned people. Computer systems offer features to articulate preferences of tasks and times. Therefore the work planning process could be more democratic, since the workers could participate in the decision-making procedure actively. The article investigates how a decision situation can be modelled in order to design a technical support system. In addition it will be analysed as to which social and group dynamic aspects play crucial roles–from a system designer's view. Empirical data on time management processes of various working groups serves as discussion example.     

The distorted hand metric representation serves both perception and action

ABSTRACT

The representation of our body location is achieved by integrating sensorimotor inputs with information about our body size. Previous studies have shown that the metric representation of our hand, also called the body model, is distorted, namely overestimated in width and underestimated in length, although we are able to perform accurate fine movements. Considering the known dissociation between action-oriented and perception-oriented body representations, we asked whether the body model mainly serves body perception or whether it is also involved in movements. Twenty-one healthy adults were administered with the Localization Task (LT) which required the participants to localise the perceived position of their unseen hand by means of a stick held by their other hand, and the Proprioceptive Matching Task (PMT) which required the participants to match their perceived hand position with a visual target. LT and PMT maps were compared with the actual hand sizes. We found that the PMT map exhibited similar body model distortions, confirming that the body model is involved in motor programming. Furthermore, we observed that a partial adjustment of the distortions occurs in a motor condition.     

The fundamentality of group principles and perceived group entitativity

We argue that the level of consensus about a set of social identity principles, and their perceived fundamentality, can influence the degree to which members perceive their group as an entity. This idea was explored through an experiment in which participants judged the entitativity of specific (in)groups on the basis of the distribution of the opinions held by their members about three identity-related principles that participants had previously rated for fundamentality. The results demonstrated that the more fundamental a principle was judged to be in comparison to other principles, the more important consensus about that principle was for producing group entitativity, relative to consensus about other principles.     

The problem of the additive constant and eigenvalues in metric multidimensional scaling

This paper is concerned with the additive constant problem in metric multidimensional scaling. First the influence of the additive constant on eigenvalues of a scalar product matrix is discussed. The second part of this paper is devoted to the introduction of a new formulation of the additive constant problem. A solution is given for fixed dimensionality, by maximizing a normalized index of fit with a gradient method. An experimental computation has shown that the author's solution is accurate and easy to follow.