Spatial attention increases performance but not subjective confidence in a discrimination task

Selective attention to a target yields faster and more accurate responses. Faster response times, in turn, are usually associated with increased subjective confidence. Could the decrease in reaction time in the presence of attention therefore simply reflect a shift toward more confident responses? We here addressed the extent to which attention modulates accuracy, processing speed, and confidence independently. To probe the effect of spatial attention on performance, we used two attentional manipulations of a visual orientation discrimination task. We demonstrate that spatial attention significantly increases accuracy, whereas subjective confidence measures reveal overconfidence in non-attended stimuli. At constant confidence levels, reaction times showed a significant decrease (by 15–49%, corresponding to 100–250 ms). This dissociation of objective performance and subjective confidence suggests that attention and awareness, as measured by confidence, are distinct, albeit related, phenomena

Three Essays on the German SME Bond Market

Die vorliegende Dissertation befasst sich mit dem Markt für Mittelstandsanleihen, der 2010 in Deutschland etabliert wurde und nur wenige Jahre später, im Zusammenhang mit massiven Anleiheausfällen, zusammengebrochen ist. Ziel der Arbeit ist es zu analysieren, welche Faktoren zum Zusammenbruch des Marktes beigetragen haben könnten, um besser zu verstehen, wie mittelständischen Unternehmen der Zugang zum Kapitalmarkt erleichtert werden kann. Das erste Kapitel analysiert die Entscheidung, sich am Markt für Mittelstandsanleihen zu finanzieren. Verschiedene Theorien versuchen zu erklären, welche Unternehmen sich vorrangig über Banken und welche sich am Kapitalmarkt finanzieren. Entgegen der Theorie haben sich vorwiegend Unternehmen mit schlechterer Kreditwürdigkeit am Markt für Mittelstandsanleihen finanziert. Das zweite Kapitel untersucht, ob der Zugang zum Markt für Mittelstandsanleihen finanzielle Beschränkungen aufheben und so Investitionen anstoßen konnte. Eine alternative Motivation könnte jedoch auch sein, dass Unternehmen sich Geld von gutgläubigen Privatinvestoren geliehen haben, um die Insolvenz zu verschleppen. Emittenten von Mittelstandsanleihen waren zwar finanziell eingeschränkt, investierten jedoch weniger als erwartet. Eine große Anzahl der Emittenten wäre ohne die Mittelstandsanleihe bereits im Jahr der Emission zahlungsunfähig gewesen. Das dritte Kapitel untersucht vor dem Hintergrund der massiven Zahlungsausfälle, ob Investoren in der Lage waren, Unternehmen mit hohem Risiko von solchem mit niedrigerem Risiko zu unterscheiden. Erschwert wurde die korrekte Einschätzung der Risiken durch eine starke Präsenz von Privatinvestoren sowie einer Inflation der Anleiheratings. Die Ergebnisse deuten darauf hin, dass Investoren nicht in der Lage waren, riskante von weniger riskanten Mittelstandsanleihen zu unterscheiden. Dies könnte zum Zusammenbruch des Marktes beigetragen haben, da dieser für hochqualitative Unternehmen letztendlich zu teuer war.This dissertation explores the German market for SME bonds that was established in 2010 and collapsed soon after, when one third of the listed bonds defaulted. The first paper studies the choice to enter the German MBond market. The results show that MBond issuers in contrast to theoretical predictions and prior empirical findings, have lower credit quality. The second paper examines to the extent to which the main goal of the MBond market, alleviating nancial constraints in order to spur firm investment, has been achieved. Indeed, a major fraction of MBond issuers have been finnancially constrained in the year prior to issuance. However, MBond issuers appear to invest less than expected. The results are more in favor of the alternative explanation that MBond issuers timed the market and exploited a window of opportunity to issue junk bonds to retail investors, in order to nance future losses and avoid or postpone bankruptcy. In the light of the high default rate and the final collapse of the market, the third paper analyzes whether investors were able to distinguish between high and low risk MBonds. Rating in ation in the MBond market could have distorted the information channel, hampering investors' risk assessment of the MBonds. The results indicate that di erences in default risk were not adequately reflected in MBond yield spreads. Thus, it appears that MBond investors were not able to distinguish between high and low quality issuers. As a consequence, the MBond market was relatively more expensive for high quality issuers than it was for their low quality counterparts, which may have contributed to the near-total collapse of the market

Online Communities: Influence on Members Brand Loyalty and Purchase Intent

With the emergence of new media technologies it is becoming easier for brands to interact and engage with consumers in an attempt to build brand loyalty. One trend gaining popularity is the use of online branded communities, purpose-built social networks with focus (direct or indirect) on a brand. Branded communities tend to give more specific value to the brand owner and the members, allowing for greater communication and collaboration around the brand. Using the uses and gratification as a theoretical framework this study set out to explore the influence online brand communities have on members brand loyalty and intent to purchase. The method used was a survey administered in the form of an online questionnaire was administered to members of online brand communities

Cortical topography of intracortical inhibition influences the speed of decision making

The neocortex contains orderly topographic maps; however, their functional role remains controversial. Theoretical studies have suggested a role in minimizing computational costs, whereas empirical studies have focused on spatial localization. Using a tactile multiple-choice reaction time (RT) task before and after the induction of perceptual learning through repetitive sensory stimulation, we extend the framework of cortical topographies by demonstrating that the topographic arrangement of intracortical inhibition contributes to the speed of human perceptual decision-making processes. RTs differ among fingers, displaying an inverted U-shaped function. Simulations using neural fields show the inverted U-shaped RT distribution as an emergent consequence of lateral inhibition. Weakening inhibition through learning shortens RTs, which is modeled through topographically reorganized inhibition. Whereas changes in decision making are often regarded as an outcome of higher cortical areas, our data show that the spatial layout of interaction processes within representational maps contributes to selection and decision-making processes

Atividade antibacteriana de fibras têxteis contendo nanopartículas de poli (óxido de etileno-b-ácido lático) com óleos essenciais incorporados

Neste estudo foi avaliada a atividade antibacteriana de fibras têxteis contendo nanopartículas de poli(óxido de etileno-b-ácido lático) com óleos essenciais incorporados. O sistema desenvolvido demonstrou atividade antibacteriana contra Staphylococcus aureus, sugerindo seu potencial uso como agente antibacteriano. Foram utilizados copolímeros dibloco baseados em um bloco fixo de PEO (5kDa) e dois segmentos de PLA diferentes (4,5 e 10kDa). A morfologia, a eficiência do encapsulamento, a interação da blenda de óleos essenciais (incluindo, lavanda, melaleuca, tomilho, cravo, cedro e capim limão) e polímero e a cinética de liberação do agente ativo nas nanopartículas foram avaliadas. O raio hidrodinâmico das nanopartículas determinado pela dispersão da luz foi afetado pelo tamanho do bloco de poli(ácido lático). A liberação in vitro sugere que a barreira polimérica é capaz de controlar a liberação de óleo. A atividade antibacteriana foi mais eficaz em tecidos com fibras arranjadas aleatoriamente. De acordo com estudos da literatura, nanopartículas obtidas de copolímeros com menor massa molar de PLA favoreceram a liberação da mistura de óleos essenciais. O processo de incorporação dos óleos essenciais nas fibras têxteis mostrou-se eficiente sugerindo viabilidade quanto ao uso desse sistema no controle antibacteriano. Os sistemas desenvolvidos oferecem uma nova estratégia para a liberação controlada com atividade antibacteriana e apresentam potenciais aplicações na indústria calçadista.Palavras-chave: nanopartículas, óleos essenciais, efeito antibacteriano.

Age-Related Attenuation of Dominant Hand Superiority

The decline of motor performance of the human hand-arm system with age is well-documented. While dominant hand performance is superior to that of the non-dominant hand in young individuals, little is known of possible age-related changes in hand dominance. We investigated age-related alterations of hand dominance in 20 to 90 year old subjects. All subjects were unambiguously right-handed according to the Edinburgh Handedness Inventory. In Experiment 1, motor performance for aiming, postural tremor, precision of arm-hand movement, speed of arm-hand movement, and wrist-finger speed tasks were tested. In Experiment 2, accelerometer-sensors were used to obtain objective records of hand use in everyday activities

The Spatial and Temporal Construction of Confidence in the Visual Scene

Human subjects can report many items of a cluttered field a few hundred milliseconds after stimulus presentation. This memory decays rapidly and after a second only 3 or 4 items can be stored in working memory. Here we compared the dynamics of objective performance with a measure of subjective report and we observed that 1) Objective performance beyond explicit subjective reports (blindsight) was significantly more pronounced within a short temporal interval and within specific locations of the visual field which were robust across sessions 2) High confidence errors (false beliefs) were largely confined to a small spatial window neighboring the cue. The size of this window did not change in time 3) Subjective confidence showed a moderate but consistent decrease with time, independent of all other experimental factors. Our study allowed us to asses quantitatively the temporal and spatial access to an objective response and to subjective reports

A Common Cortical Circuit Mechanism for Perceptual Categorical Discrimination and Veridical Judgment

Perception involves two types of decisions about the sensory world: identification of stimulus features as analog quantities, or discrimination of the same stimulus features among a set of discrete alternatives. Veridical judgment and categorical discrimination have traditionally been conceptualized as two distinct computational problems. Here, we found that these two types of decision making can be subserved by a shared cortical circuit mechanism. We used a continuous recurrent network model to simulate two monkey experiments in which subjects were required to make either a two-alternative forced choice or a veridical judgment about the direction of random-dot motion. The model network is endowed with a continuum of bell-shaped population activity patterns, each representing a possible motion direction. Slow recurrent excitation underlies accumulation of sensory evidence, and its interplay with strong recurrent inhibition leads to decision behaviors. The model reproduced the monkey's performance as well as single-neuron activity in the categorical discrimination task. Furthermore, we examined how direction identification is determined by a combination of sensory stimulation and microstimulation. Using a population-vector measure, we found that direction judgments instantiate winner-take-all (with the population vector coinciding with either the coherent motion direction or the electrically elicited motion direction) when two stimuli are far apart, or vector averaging (with the population vector falling between the two directions) when two stimuli are close to each other. Interestingly, for a broad range of intermediate angular distances between the two stimuli, the network displays a mixed strategy in the sense that direction estimates are stochastically produced by winner-take-all on some trials and by vector averaging on the other trials, a model prediction that is experimentally testable. This work thus lends support to a common neurodynamic framework for both veridical judgment and categorical discrimination in perceptual decision making

Isolation und Charakterisierung der Toxine des phytopathogenen Bakteriums Clavibakter michiganese subsp. nebraskense

Available from TIB Hannover: DW 4269 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman