Deduction chains for common knowledge

Deduction chains represent a syntactic and in a certain sense constructive method for proving completeness of a formal system. Given a formula , the deduction chains of are built up by systematically decomposing into its subformulae. In the case where is a valid formula, the decomposition yields a (usually cut-free) proof of . If is not valid, the decomposition produces a countermodel for . In the current paper, we extend this technique to a semiformal system for the Logic of Common Knowledge. The presence of fixed point constructs in this logic leads to potentially infinite-length deduction chains of a non-valid formula, in which case fairness of decomposition requires special attention. An adequate order of decomposition also plays an important role in the reconstruction of the proof of a valid formula from the set of its deduction chains.     

Coping with the stress of a painful medical procedure

To evaluate its effect on procedure-related distress, the focus of attention was manipulated by providing training to hospitalized acute burn patients (n=42). Participants were randomly assigned to attention focusing (i.e. attending to procedural sensations) or music distraction (i.e. attention diverting) coping interventions, or to usual care during the target dressing change. Coping behavior (i.e. distraction, focusing, and three confounding methods, ignoring, catastrophizing, reinterpreting), tension and intrusiveness were evaluated 24 h retrospectively (i.e. for the prior procedure), during the targeted procedure, and 30 min after the target procedure. When coping during the target procedure by ignoring, reinterpreting, and catastrophizing were covaried, the music distraction group experienced significantly fewer intrusions, and the attention focus group had more intrusions. Additionally, secondary analyses revealed that coping by ignoring during the prior day's procedure significantly predicted higher procedural tension during, and more intrusions following, the targeted procedure. Suppression-based forms of emotion-focused coping may be enhanced by training in the use of an explicit distractor.     

The currency of procurement cost

As the number of instrtumental responses required to procure access to food is increased, animals decrease the frequency of initiating meals and increase meal size, conserving total intake while limiting the increase in the overall cost of feeding. In two studies, one using wheel turns and one using bar presses as the instrumental response, we asked whether freely feeding laboratory rats measure cost according to the energy or the time they expend. In each study we varied both the price (i.e., number of wheel turns or bar presses) and the force required to make a response (i.e., torque on the wheel or weight of the bar). Price affected both procurement time (from the first to the last procurement response) and procurement work, whereas torque and bar weight affected work without altering time in most cases. Meal patterns were altered by all manipulations of price, but changes in torque and bar weight had little effect on meal patterns, except in the conditions in which they altered procurement time. These results suggest that time is a critical currency of procurement cost in rats.     

Every light has its shadow: a longitudinal study of transformational leadership and leaders’ emotional exhaustion

This study investigated the effects of transformational and laissez‐faire leadership on leaders’ own emotional exhaustion over time. Participants were 2,324 subordinates and 76 supervisors of a services company in Germany. Regression analysis revealed direct longitudinal health‐hampering effects of transformational and laissez‐faire leadership on leaders’ emotional exhaustion. Building on Hobfoll's Conservation of Resources theory (1989), our results showed that the longitudinal health‐hampering effects of transformational leadership would be particularly pronounced for leaders with high levels of organization‐based self‐esteem. Our findings extend the research on potential dark sides of transformational and laissez‐faire leadership as well as organization‐based self‐esteem by focusing on leader‐centered outcomes.     

Negativity bias in defeasible reasoning

In defeasible reasoning, initially drawn conclusions can be withdrawn in light of new information. In this paper, we examine how the conclusions drawn from conditionals describing positive or negative situations can be defeated by subsequent negative or positive information, respectively. Participants were confronted with conditionals of the form “If [situation], then I am happy/sad” which were either followed by no additional information or by additional information describing situations of the same or the opposite valence. The participant's task was to decide on a question asking for a possible conclusion (“Am I happy?” vs. “Am I sad?”). We found a negativity bias in defeasible reasoning: negative information defeated positively charged conclusions more strongly than positive information defeated negatively charged conclusions. We discuss our results in relation to the new psychology of reasoning.     

Holistic processing improves change detection but impairs change identification

It has been just over a century since Gestalt psychologists described the factors that contribute to the holistic processing of visually presented stimuli. Recent research indicates that holistic processing may come at a cost; specifically, the perception of holistic forms may reduce the visibility of constituent parts. In the present experiment, we examined change detection and change identification accuracy with Kanizsa rectangle patterns that were arranged to either form a Gestalt whole or not. Results from an experiment with 62 participants support this trade-off in processing holistic forms. Holistic processing improved the detection of change but obstructed its identification. Results are discussed in terms of both their theoretical significance and their application in areas ranging from baggage screening and the detection of changes in radiological images to the systems that are used to generate composite images of perpetrators on the basis of eyewitness reports.     

Creative at Each Age: Age‐Related Differences in Drivers of Workplace Creativity from an Experience Sampling Study

Creativity and innovation are essential agents for change processes and accelerating technical development. Having to face challenges, such as demographic change, organizations require individuals who are creative and innovative at each age. Previous research identified affect as a crucial determinant of creativity, even though empirical findings showed inconsistencies. Drawing on literature on age‐related changes in affective experiences, we investigated the moderating effect of employees’ age on the association between daily positive and negative affect and creativity using a daily diary study. A total of 116 employees responded to daily questionnaires twice a day over five consecutive working days. As expected, hierarchical linear modeling analyses revealed differential effects regarding the affect‐creativity association, dependent on employees’ age. Although older employees were most creative on days when they experienced a high level of positive affect (compared to their mean level of positive affect), younger employees were particularly creative when experiencing negative affect (compared to their mean level of negative affect). We discuss practical implications on how organizations could provide creativity‐enhancing work environments for employees at each age.