Mental representation of length and weight series and transitive inferences in young children

Forty-eight second graders (8 years of age) were trained on length or weight relationships between adjacent members of a five-term series of colored objects. Feedback was visual and of either minimal or strong salience. Differences in weight were assessed by either a balance scale or a spring scale. Results showed that more salient visual feedback reduced the learning effort for length but not for weight comparisons. After training children were tested on all possible object pairs. Children's comparisons of items by length were very accurate in contrast to their comparisons by weight. An explanation for these findings is suggested by the data from a group of 6-year-olds who were trained on two independent pairs of a four-term series. Test results showed that subjects spontaneously encoded absolute lengths but tended to ignore information about the absolute weight of objects. It is suggested that high test accuracy depends on stimulus material for which the absolute values of the relevant dimension are encoded. The implications for taking test performance as an indicator of “transitive reasoning” ability are discussed.     

Mixtures of conditional mean- and covariance-structure models

Models and parameters of finite mixtures of multivariate normal densities conditional on regressor variables are specified and estimated. We consider mixtures of multivariate normals where the expected value for each component depends on possibly nonnormal regressor variables. The expected values and covariance matrices of the mixture components are parameterized using conditional mean- and covariance-structures. We discuss the construction of the likelihood function, estimation of the mixture model with regressors using three different EM algorithms, estimation of the asymptotic covariance matrix of parameters and testing for the number of mixture components. In addition to simulation studies, data on food preferences are analyzed.The authors are grateful to Donald B. Rubin and Michael E. Sobel for critical reading of a first draft of this paper and to three anonymous reviewers ofPsychometrika for their helpful comments and suggestions. The research of the first and the third author was supported by a grant from the Deutsche Forschungsgemeinschaft.     

The role of language familiarity in voice identification

Four experiments examined the effects of language characteristics on voice identification. In Experiment 1, monolingual English listeners identified bilinguals' voices much better when they spoke English than when they spoke German. The opposite outcome was found in Experiment 2, in which the listeners were monolingual in German. In Experiment 3, monolingual English listeners also showed better voice identification when bilinguals spoke a familiar language (English) than when they spoke an unfamiliar one (Spanish). However, English-Spanish bilinguals hearing the same voices showed a different pattern, with the English-Spanish difference being statistically eliminated. Finally, Experiment 4 demonstrated that, for English-dominant listeners, voice recognition deteriorates systematically as the passage being spoken is made less similar to English by rearranging words, rearranging syllables, and reversing normal text. Taken together, the four experiments confirm that language familiarity plays an important role in voice identification.     

Answer Sets and Qualitative Optimization

One of the major reasons for the success of answer set programmingin recent years was the shift from a theorem proving to a constraintprogramming view: problems are represented such that stablemodels, respectively answer sets, rather than theorems correspondto solutions. This shift in perspective proved extremely fruitfulin many areas. We believe that going one step further from a"hard" to a "soft" constraint programming paradigm, or, in otherwords, to a paradigm of qualitative optimization, will proveequally fruitful. In this paper we try to support this claimby showing that several generic problems in logic based problemsolving can be understood as qualitative optimization problems,and that these problems have simple and elegant formulationsgiven adequate optimization constructs in the knowledge representationlanguage.     

Youth suicide risk factors and attitudes in New York and Vienna: a cross-cultural comparison

The prevalence of suicide risk factors and attitudes about suicide and help-seeking among New York and Viennese adolescents were compared in order to explore possible cross-cultural differences. Viennese adolescents exhibited higher rates of depressive symptomatology than their New York counterparts and had more first-hand experience with suicidal peers. More attribution of suicide to mental illness was reported in Vienna; yet Viennese youth were less likely than New York adolescents to recognize the seriousness of suicide threats. Help-seeking patterns of Viennese adolescents were influenced by their setting a high value on confidentiality. These cross-cultural differences may reflect the limited exposure of Austrian youth to school-based suicide prevention programs. The findings highlight the need of taking the sociocultural context into consideration in the planning of youth suicide prevention strategies.     

Investigating the dopaminergic basis of extraversion in humans: A multilevel approach

A recent theory suggests that the agency facet of Extraversion (E) is based on brain dopamine (DA). The paucity of human data relevant to this model is probably due to the lack of widely accessible noninvasive psychophysiological indices and well-established behavioral measures sensitive to both E and manipulations of DA activity. Aiming to identify such measures, the authors assessed the electroencephalogram and n-back task performance in groups of introverts and extraverts after administration of either placebo or a selective DA D2 receptor antagonist. As predicted, the antagonist's effects on n-back reaction time measures and frontal versus parietal electroencephalogram theta activity were strongly and specifically modulated by E. New research avenues and theoretical extensions suggested by these results are discussed.