Showing papers by "University of Konstanz published in 2010"

Control and interference in task switching--a review.

Abstract: The task-switching paradigm offers enormous possibilities to study cognitive control as well as task interference. The current review provides an overview of recent research on both topics. First, we review different experimental approaches to task switching, such as comparing mixed-task blocks with single-task blocks, predictable task-switching and task-cuing paradigms, intermittent instructions, and voluntary task selection. In the 2nd part, we discuss findings on preparatory control mechanisms in task switching and theoretical accounts of task preparation. We consider preparation processes in two-stage models, consider preparation as an all-or-none process, address the question of whether preparation is switch-specific, reflect on preparation as interaction of cue encoding and memory retrieval, and discuss the impact of verbal mediation on preparation. In the 3rd part, we turn to interference phenomena in task switching. We consider proactive interference of tasks and inhibition of recently performed tasks indicated by asymmetrical switch costs and n-2 task-repetition costs. We discuss stimulus-based interference as a result of stimulus-based response activation and stimulus-based task activation, and response-based interference because of applying bivalent rather than univalent responses, response repetition effects, and carryover of response selection and execution. In the 4th and final part, we mention possible future research fields.

Social Preferences, Beliefs, and the Dynamics of Free Riding in Public Goods Experiments

Abstract: One lingering puzzle is why voluntary contribu tions to public goods decline over time in experimental and real-w orld settings. We show that the decl ine of cooperation is driven by individual preferences for im perfect conditional cooperation. Many people’s desire to contribute less than oth ers, rather than changing beliefs of what others will contr ibute over time or people’s heterogeneity in preferences makes voluntary cooperation fragile. Universal free riding thus even tually emerges, despite the fact tha t m ost peop le a re not selfis h. (JEL C91, C72, H41, D64)

Boredom in achievement settings: Exploring control–value antecedents and performance outcomes of a neglected emotion.

Abstract: The linkages of achievement-related boredom with students' appraisals and performance outcomes were examined in a series of 5 exploratory, cross-sectional, and predictive investigations. Studies 1 and 2 assessed students' boredom in a single achievement episode (i.e., state achievement boredom); Studies 3, 4, and 5 focused on their habitual boredom (i.e., trait achievement boredom). Samples consisted of university students from two different cultural contexts (North America and Germany). In line with hypotheses derived from Pekrun's (2006) control-value theory of achievement emotions, achievement-related subjective control and value negatively predicted boredom. In turn, boredom related positively to attention problems and negatively to intrinsic motivation, effort, use of elaboration strategies, self-regulation, and subsequent academic performance. Findings were consistent across different constructs (state vs. trait achievement boredom), methodologies (qualitative, cross-sectional, and predictive), and cultural contexts. The research is discussed with regard to the underdeveloped literature on achievement emotions.

Diary Studies in Organizational Research: An Introduction and Some Practical Recommendations

Abstract: In recent years, researchers in work and organizational psychology have increasingly become interested in short-term processes and everyday experiences of working individuals. Diaries provide the necessary means to examine these processes. Although diary studies have become more popular in recent years, researchers not familiar with this method still find it difficult to get access to the required knowledge. In this paper, we provide an introduction to this method of data collection. Using two diary study examples, we discuss methodological issues researchers face when planning a diary study, examine recent methodological developments, and give practical recommendations. Topics covered include different types of diary studies, the research questions to be examined, compliance and the issue of missing data, sample size, and issues of analyses.

Highly enantioselective synthesis and cellular evaluation of spirooxindoles inspired by natural products

Abstract: A Lewis-acid-catalysed 1,3-dipolar cycloaddition provides rapid access to a variety of substituted spirooxindoles. Initial cellular evaluations supports the view that compound collections based on natural-product-inspired scaffolds constructed with complex stereochemistry, and decorated with assorted substituents, will be a rich source of compounds with diverse bioactivity.

Staying Well and Engaged When Demands Are High: The Role of Psychological Detachment.

Abstract: The authors of this study examined the relation between job demands and psychological detachment from work during off-job time (i.e., mentally switching off) with psychological well-being and work engagement. They hypothesized that high job demands and low levels of psychological detachment predict poor well-being and low work engagement. They proposed that psychological detachment buffers the negative impact of high job demands on well-being and work engagement. A longitudinal study (12-month time lag) with 309 human service employees showed that high job demands predicted emotional exhaustion, psychosomatic complaints, and low work engagement over time. Psychological detachment from work during off-job time predicted emotional exhaustion and buffered the relation between job demands and an increase in psychosomatic complaints and between job demands and a decrease in work engagement. The findings of this study suggest that psychological detachment from work during off-job time is an important factor that helps to protect employee well-being and work engagement.

Active magneto-plasmonics in hybrid metal–ferromagnet structures

Abstract: Active switching of plasmons by an external magnetic field is demonstrated in a metal–ferromagnet–metal structure. The strong modulation, combined with possible all-optical magnetization reversal induced by femtosecond light pulses, opens the door to ultrafast magneto-plasmonic switching.

Snapshots of cooperative atomic motions in the optical suppression of charge density waves

Abstract: The development of tabletop femtosecond electron diffraction sources has provided an alternative way of observing atomic motions in crystalline materials. This technique has now been applied to the charge-density-wave material 1T-TaS2, in which modulation of the electron density is accompanied by a periodic lattice distortion. Previous time-resolved studies have revealed the dynamics of the electronic charge density wave, but until now the dynamics of the lattice system has been only indirectly inferred. In this new experiment, atomic motions were observed in response to a 140 femtosecond optical pulse. Periodic lattice distortion was seen to collapse on an exceptionally fast timescale (about 250 fs), indicative of an electronically driven process involving a high degree of cooperativity. The surprisingly high degree of cooperation in the observed structural dynamics between the electronic and lattice system illustrates the potential for the technique in studies of strongly correlated systems.

Spectral Analysis of Signed Graphs for Clustering, Prediction and Visualization.

Abstract: We study the application of spectral clustering, prediction and visualization methods to graphs with negatively weighted edges. We show that several characteristic matrices of graphs can be extended to graphs with positively and negatively weighted edges, giving signed spectral clustering methods, signed graph kernels and network visualization methods that apply to signed graphs. In particular, we review a signed variant of the graph Laplacian. We derive our results by considering random walks, graph clustering, graph drawing and electrical networks, showing that they all result in the same formalism for handling negatively weighted edges. We illustrate our methods using examples from social networks with negative edges and bipartite rating graphs.

Evidence of selection upon genomic GC-content in bacteria

Abstract: The genomic GC-content of bacteria varies dramatically, from less than 20% to more than 70%. This variation is generally ascribed to differences in the pattern of mutation between bacteria. Here we test this hypothesis by examining patterns of synonymous polymorphism using datasets from 149 bacterial species. We find a large excess of synonymous GC→AT mutations over AT→GC mutations segregating in all but the most AT-rich bacteria, across a broad range of phylogenetically diverse species. We show that the excess of GC→AT mutations is inconsistent with mutation bias, since it would imply that most GC-rich bacteria are declining in GC-content; such a pattern would be unsustainable. We also show that the patterns are probably not due to translational selection or biased gene conversion, because optimal codons tend to be AT-rich, and the excess of GC→AT SNPs is observed in datasets with no evidence of recombination. We therefore conclude that there is selection to increase synonymous GC-content in many species. Since synonymous GC-content is highly correlated to genomic GC-content, we further conclude that there is selection on genomic base composition in many bacteria.

Development of Mathematics Interest in Adolescence: Influences of Gender, Family, and School Context

Abstract: This study investigated adolescents’ developmental trajectories of mathematics interest and explored related effects of gender, family, and school context.Latent growth curvemodelingwas usedtoanalyzelongitudinaldataofN 53,193students(51%female)fromgrades5to9fromall3 ability tracks of the German state school system. Annual assessments involved student questionnaires on interest in mathematics, perceptions of classroom characteristics (classroom values for mathematics, mathematics teacher enthusiasm), as well as parent questionnaires regarding family values for mathematics. Results indicated a downward trend of students’ mathematics interest that plateaued in later years, with high variability in mean levels, but little variability in the shape of the growth trajectories. Boys reported higher mathematics interest than girls, but similar downward growth trajectories. Students from the lowest ability track showed more favorable interest trajectories than students from the middle and highest tracks. Family values andclassroomcharacteristicswerepositivelyrelatedtowithin-personlevelsofinterestovertime and to average individual levels of interest, but not to growth parameters. Theoretical and practical implications are discussed.

Parallel Olfactory Systems in Insects: Anatomy and Function

Abstract: A striking commonality across insects and vertebrates is the recurring presence of parallel olfactory subsystems, suggesting that such an organization has a highly adaptive value. Conceptually, two different categories of parallel systems must be distinguished. In one, specific sensory organs or processing streams analyze different chemical stimuli (segregate parallel systems). In the other, similar odor stimuli are processed but analyzed with respect to different features (dual parallel systems). Insects offer many examples for both categories. For example, segregate parallel systems for different chemical stimuli are realized in specialized neuronal streams for processing sex pheromones and CO2. Dual parallel streams related to similar or overlapping odor stimuli are prominent in Hymenoptera. Here, a clear separation of sensory tracts to higher-order brain centers is present despite no apparent differences regarding the classes or categories of olfactory stimuli being processed. In this paper, we review...

Synthesis of a single cycle of light with compact erbium-doped fibre technology

Abstract: The advent of self-referenced optical frequency combs1,2 has sparked the development of novel areas in ultrafast sciences such as attosecond technology3,4 and the synthesis of arbitrary optical waveforms5,6. Few-cycle light pulses are key to these time-domain applications, driving a quest for reliable, stable and cost-efficient mode-locked laser sources with ultrahigh spectral bandwidth. Here, we present a set-up based entirely on compact erbium-doped fibre technology, which produces single cycles of light. The pulse duration of 4.3 fs is close to the shortest possible value for a data bit of information transmitted in the near-infrared regime. These results demonstrate that fundamental limits for optical telecommunications are accessible with existing fibre technology and standard free-space components. Based on a passively phase-locked superposition of a dispersive wave and a soliton from two branches of a femtosecond Er-doped fibre laser, researchers demonstrate that single cycles of light can be achieved using existing fibre technology and standard free-space components. The pulses have a pulse duration of 4.3 fs, close to the shortest possible value for a data bit of information transmitted in the near-infrared.

Proline metabolism and transport in plant development

Abstract: Proline fulfils diverse functions in plants. As amino acid it is a structural component of proteins, but it also plays a role as compatible solute under environmental stress conditions. Proline metabolism involves several subcellular compartments and contributes to the redox balance of the cell. Proline synthesis has been associated with tissues undergoing rapid cell divisions, such as shoot apical meristems, and appears to be involved in floral transition and embryo development. High levels of proline can be found in pollen and seeds, where it serves as compatible solute, protecting cellular structures during dehydration. The proline concentrations of cells, tissues and plant organs are regulated by the interplay of biosynthesis, degradation and intra- as well as intercellular transport processes. Among the proline transport proteins characterized so far, both general amino acid permeases and selective compatible solute transporters were identified, reflecting the versatile role of proline under stress and non-stress situations. The review summarizes our current knowledge on proline metabolism and transport in view of plant development, discussing regulatory aspects such as the influence of metabolites and hormones. Additional information from animals, fungi and bacteria is included, showing similarities and differences to proline metabolism and transport in plants.

Dissociation Following Traumatic Stress Etiology and Treatment

Abstract: We postulate that the cascade ''Freeze-Flight-Fight-Fright-Flag-Faint'' is a coherent sequence of six fear responses that escalate as a function of defense possibilities and proximity to danger during life-threat. The actual sequence of trauma-related response dispositions acted out in an extremely dangerous situation therefore depends on the appraisal of the threat by the organism in relation to her/his own power to act (e.g., age and gender) as well as the perceived characteristics of threat and perpetrator. These reaction patterns provide optimal adaption for particular stages of imminence. Subsequent to the traumatic threats, portions of the experience may be replayed. The actual individual cascade of defense stages a survivor has gone through during the traumatic event will repeat itself every time the fear network, which has evolved peritraumatically, is activated again (i.e., through internal or external triggers or, e.g., during exposure therapy).When a parasympathetically dominated ''shut- down'' was the prominent peri-traumatic response during the traumatic incident, comparable dissociative responses may dominate responding to subsequently experienced threat and may also reappear when the traumatic memory is reactivated. Repeated experience of traumatic stress forms a fear network that can become pathologically detached from contextual cues such as time and location of the danger, a condition which manifests itself as posttraumatic stress disorder (PTSD). Intrusions, for example, can therefore be understood as repetitive displays of fragments of the event, which would then, depending on the dominant physiological response during the threat, elicit a corresponding combination of hyperarousal and dissociation. We suggest that trauma treatment must therefore differentiate between patients on two dimensions: those with peritraumatic sympathetic activation versus those who went down the whole defense cascade, which leads to parasympathetic dominance during the trauma and a corresponding replay of physiological and dissociative responding, when reminded. The differential management of dissociative stages (''fright'' and ''faint'') has important treatment implications.

Biomineralization: A crystal-clear view

Abstract: The mechanisms of biomineralization remain hotly debated. Now high-resolution microscopy yields unsurpassed insight into mechanisms relevant both to the biomineralization of bone and teeth and to pathological mineralization.

Syntrophic butyrate and propionate oxidation processes: from genomes to reaction mechanisms

Abstract: In anoxic environments such as swamps, rice fields and sludge digestors, syntrophic microbial communities are important for decomposition of organic matter to CO2 and CH4. The most difficult step is the fermentative degradation of short-chain fatty acids such as propionate and butyrate. Conversion of these metabolites to acetate, CO2, formate and hydrogen is endergonic under standard conditions and occurs only if methanogens keep the concentrations of these intermediate products low. Butyrate and propionate degradation pathways include oxidation steps of comparably high redox potential, i.e. oxidation of butyryl-CoA to crotonyl-CoA and of succinate to fumarate, respectively, that require investment of energy to release the electrons as hydrogen or formate. Although investigated for several decades, the biochemistry of these reactions is still not completely understood. Genome analysis of the butyrate-oxidizing Syntrophomonas wolfei and Syntrophus aciditrophicus and of the propionate-oxidizing Syntrophobacter fumaroxidans and Pelotomaculum thermopropionicum reveals the presence of energy-transforming protein complexes. Recent studies indicated that S. wolfei uses electron-transferring flavoproteins coupled to a menaquinone loop to drive butyryl-CoA oxidation, and that S. fumaroxidans uses a periplasmic formate dehydrogenase, cytochrome b:quinone oxidoreductases, a menaquinone loop and a cytoplasmic fumarate reductase to drive energy-dependent succinate oxidation. Furthermore, we propose that homologues of the Thermotoga maritima bifurcating [FeFe]-hydrogenase are involved in NADH oxidation by S. wolfei and S. fumaroxidans to form hydrogen

Decision Processes in Human Performance Monitoring

Abstract: The ability to detect and compensate for errors is crucial in producing effective, goal-directed behavior Human error processing is reflected in two event-related brain potential components, the error-related negativity (Ne/ERN) and error positivity (Pe), but the functional significance of both components remains unclear Our approach was to consider error detection as a decision process involving an evaluation of available evidence that an error has occurred against an internal criterion This framework distinguishes two fundamental stages of error detection—accumulating evidence (input), and reaching a decision (output)—that should be differentially affected by changes in internal criterion Predictions from this model were tested in a brightness discrimination task that required human participants to signal their errors, with incentives varied to encourage participants to adopt a high or low criterion for signaling their errors Whereas the Ne/ERN was unaffected by this manipulation, the Pe varied consistently with criterion: A higher criterion was associated with larger Pe amplitude for signaled errors, suggesting that the Pe reflects the strength of accumulated evidence Across participants, Pe amplitude was predictive of changes in behavioral criterion as estimated through signal detection theory analysis Within participants, Pe amplitude could be estimated robustly with multivariate machine learning techniques and used to predict error signaling behavior both at the level of error signaling frequencies and at the level of individual signaling responses These results suggest that the Pe, rather than the Ne/ERN, is closely related to error detection, and specifically reflects the accumulated evidence that an error has been committed

A dual-stage two-phase model of selective attention.

Abstract: The dual-stage two-phase (DSTP) model is introduced as a formal and general model of selective attention that includes both an early and a late stage of stimulus selection. Whereas at the early stage information is selected by perceptual filters whose selectivity is relatively limited, at the late stage stimuli are selected more efficiently on a categorical basis. Consequently, selectivity is first low but then abruptly increases during the course of stimulus processing. Although intended as a general model of selective attention, in the present study the DSTP model was applied to account for the distributional data of 3 flanker task experiments. The fit of the model to the data was not only rather good but also superior to those of alternative single-stage models with a continuously increasing selectivity. All together, the model provides a comprehensive account of how early and late stages of attention interact in the control of performance.

When planning is not enough: Fighting unhealthy snacking habits by mental contrasting with implementation intentions (MCII)

Abstract: In two experiments a self-regulatory strategy combining mental contrasting with the formation of implementation intentions (MCII) was tested for its effectiveness in diminishing unhealthy snacking habits. Study 1 (N ¼51) showed that participants in the MCII condition consumed fewer unhealthy snacks than participants in a control condition who thought about and listed healthy options for snacks. In Study 2 (N ¼59) MCII was more effective than mental contrasting or formulating implementationintentions alone and mental contrasting was found to increase perceived clarity about critical cues for unhealthy snacking. Together, these findings suggest that MCII is an effective strategy for fighting habits and that one of the underlying processes making MCII superior to implementation intentions alone may be that mental contrasting produces clarity about the critical cues for the unwanted habitual behavior. Copyright # 2010 John Wiley & Sons, Ltd.

Islam and Democracy

Abstract: Using the POLITY IV and Freedom House indices, Rowley and Smith (2009) found that countries with Muslim majorities enjoy less freedom and are less democratic than countries in which Muslims are a minority. Because the POLITY IV and Freedom House indices have been criticized on several grounds, I reinvestigate Rowley and Smith’s finding using the new Democracy-Dictatorship data from Cheibub et al. (2010). The empirical results confirm that countries with Muslim majorities are indeed less likely to be democratic.

Reducing the Expression of Implicit Stereotypes: Reflexive Control Through Implementation Intentions

Abstract: The authors tested the effectiveness of implementation intentions as a strategy for limiting the behavioral expression of implicit stereotypes. Implementation intentions are if-then plans that link an intended response to an anticipated situational cue, thereby enabling a reflexive form of control. The authors examined whether two different types of implementation intentions could improve response accuracy on the Shooter Task, a reaction time measure of implicit stereotyping. In Study 1, participants used a distraction-inhibiting implementation intention designed to engage control over the perception of goal-irrelevant stimuli (e.g., race). In Study 2, participants used a response-facilitating implementation intention designed to promote goal-directed action. Across studies, implementation intentions improved accuracy, thereby limiting the behavioral expression of implicit stereotypes. Furthermore, process dissociation analyses indicated that the distraction-inhibiting implementation intention increased controlled processing while reducing automatic stereotype activation, whereas the response-facilitating implementation intention increased only controlled processing. Implications for goal strategy approaches to reducing prejudice are discussed.

P-DBSCAN: a density based clustering algorithm for exploration and analysis of attractive areas using collections of geo-tagged photos

Abstract: The rapid spread of location-based devices and cheap storage mechanisms, as well as fast development of Internet technology, allowed collection and distribution of huge amounts of user-generated data, such as people's movement or geo-tagged photos. These types of data produce new challenges for research in different application domains. In many cases, new algorithms should be devised to better portray the phenomena under investigation. In this paper, we present P-DBSCAN, a new density-based clustering algorithm based on DBSCAN for analysis of places and events using a collection of geo-tagged photos. We thereby introduce two new concepts: (1) density threshold, which is defined according to the number of people in the neighborhood, and (2) adaptive density, which is used for fast convergence towards high density regions. Our approach is demonstrated on the area of Washington, D.C.