Heuristics and representational change in two-move matchstick tasks

Insight problems are problems where the problem solver struggles to find a solution until * aha! * the solution suddenly appears. Two contemporary theories suggest that insight problems are difficult either because problem solvers begin with an incorrect representation of the problem, or that problem solvers apply inappropriate heuristics to the problem. The relative contributions of representational change and inappropriate heuristics on the process of insight problem solving was studied with a task that required the problem solver to move two matchsticks in order to transform an incorrect arithmetic statement into a correct one. Problem solvers (N = 120) worked on two different types of two-move matchstick arithmetic problems that both varied with respect to the effectiveness of heuristics and to the degree of a necessary representational change of the problem representation. A strong influence of representational change on solution rates was found whereas the influence of heuristics had minimal effects on solution rates. That is, the difficulty of insight problems within the two-move matchstick arithmetic domain is governed by the degree of representational change required. A model is presented that details representational change as the necessary condition for ensuring that appropriate heuristics can be applied on the proper problem representation

The dynamics of search, impasse, and representational change provide a coherent explanation of difficulty in the nine-dot problem

The nine-dot problem is often used to demonstrate and explain mental impasse, creativity, and out of the box thinking. The present study investigated the interplay of a restricted initial search space, the likelihood of invoking a representational change, and the subsequent constraining of an unrestricted search space. In three experimental conditions, participants worked on different versions of the nine-dot problem that hinted at removing particular sources of difficulty from the standard problem. The hints were incremental such that the first suggested a possible route for a solution attempt; the second additionally indicated the dot at which lines meet on the solution path; and the final condition also provided non-dot locations that appear in the solution path. The results showed that in the experimental conditions, representational change is encountered more quickly and problems are solved more often than for the control group. We propose a cognitive model that focuses on general problem solving heuristics and representational change to explain problem difficulty

Insight and search in Katona’s five-square problem

Insights are often productive outcomes of human thinking. We provide a cognitive model that explains insight problem solving by the interplay of problem space search and representational change, whereby the problem space is constrained or relaxed based on the problem representation. By introducing different experimental conditions that either constrained the initial search space or helped solvers to initiate a representational change, we investigated the interplay of problem space search and representational change in Katona’s five-square problem. Testing 168 participants, we demonstrated that independent hints relating to the initial search space and to representational change had little effect on solution rates. However, providing both hints caused a significant increase in solution rates. Our results show the interplay between problem space search and representational change in insight problem solving: The initial problem space can be so large that people fail to encounter impasse, but even when representational change is achieved the resulting problem space can still provide a major obstacle to finding the solution

The King of Rockingham County and the Original Bridge to Nowhere

This chapter, reveals the story -- the clash of personalities, the economic tensions, and the political significance -- behind Rockingham County v. Luten Bridge Co. Since its publication in 1929, the opinion has proceeded to leave an impression on generations of law students. Luten Bridge, a staple in most contracts casebooks, is known today as the paradigmatic case that demonstrates the duty to mitigate damages in contract law, whereby a nonbreaching party is not compensated for performance that occurs after the other party announces an intention to breach. This chapter takes on three objectives: it identifies the case\u27s original importance, uncovers the opinion\u27s political and jurisprudential significance, and tells a remarkable story, one that arose within a heated tax revolt pitting the county\u27s farmers against its most celebrated industrialist. Much more than a crisp illustration of the duty to mitigate, Rockingham County v. The Luten Bridge Co. offers a window into a southern community\u27s struggles with a divided social order, the introduction of wealth into local politics, and a changing economy

Perioperative Pleural Drainage in Liver Transplantation: A Retrospective Analysis from a High-Volume Liver Transplant Center

BACKGROUND Pleural effusions represent a common complication after liver transplantation (LT) and chest drain (CD) placement is frequently necessary. MATERIAL AND METHODS In this retrospective cohort study, adult LT recipients between 2009 and 2016 were analyzed for pleural effusion formation and its treatment within the first 10 postoperative days. The aim of the study was to compare different settings of CD placement with regard to intervention-related complications. RESULTS Overall, 597 patients met the inclusion criteria, of which 361 patients (60.5%) received at least 1 CD within the study period. Patients with a MELD >25 were more frequently affected (75.7% versus 56.0%, P<0.001). Typically, CDs were placed in the intensive care unit (ICU) (66.8%) or in the operating room (14.1% during LT, 11.5% in the context of reoperations). In total, 97.0% of the patients received a right-sided CD, presumably caused by local irritations. Approximately one-third (35.4%) of ICU-patients required pre-interventional optimization of coagulation. Of the 361 patients receiving a CD, 15 patients (4.2%) suffered a post-interventional hemorrhage and 6 patients (1.4%) had a pneumothorax requiring further treatment. Less complications were observed when the CD was performed in the operating room compared to the ICU: 1 out 127 patients (0.8%) versus 20 out of 332 patients (6.0%); P=0.016. CONCLUSIONS CD placement occurring in the operating room was associated with fewer complications in contrast to placement occurring in the ICU. Planned CD placement in the course of surgery might be favorable in high-risk patients

Reducing the Pill Burden: Immunosuppressant Adherence and Safety after Conversion from a Twice-Daily (IR-Tac) to a Novel Once-Daily (LCP-Tac) Tacrolimus Formulation in 161 Liver Transplant Patients

Non-adherence to immunosuppressant therapy reduces long-term graft and patient survival after solid organ transplantation. The objective of this 24-month prospective study was to determine adherence, efficacy and safety after conversion of stable liver transplant (LT) recipients from a standard twice-daily immediate release Tacrolimus (IR-Tac) to a novel once-daily life cycle pharma Tacrolimus (LCP-Tac) formulation. We converted a total of 161 LT patients at baseline, collecting Tacrolimus trough levels, laboratories, physical examination data and the BAASIS(C) questionnaire for self-reported adherence to immunosuppression at regular intervals. With 134 participants completing the study period (17% dropouts), the overall adherence to the BAASIS(C) increased by 57% until month 24 compared to baseline (51% vs. 80%). Patients who required only a morning dose of their concomitant medications reported the largest improvement in adherence after conversion. The intra-patient variability (IPV) of consecutive Tacrolimus trough levels after conversion did not change significantly compared to pre-conversion levels. Despite reducing the daily dose by 30% at baseline as recommended by the manufacturer, Tac-trough levels remained stable, reflected by an increase in the concentration-dose (C/D) ratio. No episodes of graft rejection or loss occurred. Our data suggest that the use of LCP-Tac in liver transplant patients is safe and can increase adherence to immunosuppression compared to conventional IR-Tac

Early Allograft Dysfunction Increases Hospital Associated Costs After Liver Transplantation—A Propensity Score–Matched Analysis

Concepts to ameliorate the continued mismatch between demand for liver allografts and supply include the acceptance of allografts that meet extended donor criteria (ECD). ECD grafts are generally associated with an increased rate of complications such as early allograft dysfunction (EAD). The costs of liver transplantation for the health care system with respect to specific risk factors remain unclear and are subject to change. We analyzed 317 liver transplant recipients from 2013 to 2018 for outcome after liver transplantation and hospital costs in a German transplant center. In our study period, 1-year survival after transplantation was 80.1% (95% confidence interval: 75.8%-84.6%) and median hospital stay was 33 days (interquartile rage: 24), with mean hospital costs of euro115,924 (SD euro113,347). There was a positive correlation between costs and laboratory Model for End-Stage Liver Disease score (r(s) = 0.48, P < 0.001), and the development of EAD increased hospital costs by euro26,229. ECD grafts were not associated with a higher risk of EAD in our cohort. When adjusting for recipient-associated risk factors such as laboratory Model for End-Stage Liver Disease score, recipient age, and split liver transplantation with propensity score matching, only EAD and cold ischemia increased total costs. Conclusion: Our data show that EAD leads to significantly higher hospital costs for liver transplantation, which are primarily attributed to recipient health status. Strategies to reduce the incidence of EAD are needed to control costs in liver transplantation

Mir34a constrains pancreatic carcinogenesis

Several studies have shown that over 70 different microRNAs are aberrantly expressed in pancreatic ductal adenocarcinoma (PDAC), affecting proliferation, apoptosis, metabolism, EMT and metastasis. The most important genetic alterations driving PDAC are a constitutive active mutation of the oncogene Kras and loss of function of the tumour suppressor Tp53 gene. Since the MicroRNA 34a (Mir34a) is a direct target of Tp53 it may critically contribute to the suppression of PDAC. Mir34a is epigenetically silenced in numerous cancers, including PDAC, where Mir34a down-regulation has been associated with poor patient prognosis. To determine whether Mir34a represents a suppressor of PDAC formation we generated an in vivo PDAC-mouse model harbouring pancreas-specific loss of Mir34a (Kras(G12D);Mir34a(Delta/Delta)). Histological analysis of Kras(G12D);Mir34a(Delta/Delta) mice revealed an accelerated formation of pre-neoplastic lesions and a faster PDAC development, compared to Kras(G12D) controls. Here we show that the accelerated phenotype is driven by an early up-regulation of the pro-inflammatory cytokines TNFA and IL6 in normal acinar cells and accompanied by the recruitment of immune cells. Our results imply that Mir34a restrains PDAC development by modulating the immune microenvironment of PDAC, thus defining Mir34a restauration as a potential therapeutic strategy for inhibition of PDAC development

Feelings-of-Warmth Increase More Abruptly for Verbal Riddles Solved With in Contrast to Without Aha! Experience

When we are confronted with a new problem, we typically try to apply strategies that have worked in the past and which usually lead closer to the solution incrementally. However, sometimes, either during a problem-solving attempt that does not seem to lead closer to the solution, or when we have given up on problem-solving for the moment, the solution seems to appear out of nowhere. This is often called a moment of insight. Whereas the cognitive processes of getting closer to the solution are still unknown for insight problem-solving, there are two diverging theories on the subjective feeling of getting closer to the solution: (1) One that states that an intuitive feeling of closeness to the solution increases slowly, but incrementally, before it surpasses the threshold to consciousness and becomes verbalizable (=insight) (continuous approach), and (2) another that proposes that the feeling of closeness to the solution does not increase before it exceeds the threshold to consciousness (discontinuous approach). Here, we investigated the subjective feeling of closeness to the solution, assessed as feeling-of-warmth (FoW), its relationship to solving the problem versus being presented with it and whether a feeling of Aha! was experienced. Additionally, we tested whether Aha! experiences are more likely when the problem is solved actively by the participant or presented to the participant after an unsuccessful problem-solving attempt, and whether the frequency of Aha! experiences correlates with problem difficulty. To our knowledge, this is the first study combining the CRAT with FoW assessments for the named conditions (solved/unsolved, three difficulty levels, Aha!/no Aha!). We used a verbal problem-solving task, the Compound Remote Associates Task (CRAT). Our data revealed that Aha! experiences were more often reported for solutions generated by the participant compared to solutions presented after unsuccessful problem-solving. Moreover, FoW curves showed a steeper increase for the last two FoW ratings when problems were solved with Aha! in contrast to without Aha!. Based on this observation, we provide a preliminary explanation for the underlying cognitive process of solving CRA problems via insight

Hospitalization Before Liver Transplantation Predicts Posttransplant Patient Survival: A Propensity Score–Matched Analysis

In contrast to donor factors predicting outcomes of liver transplantation (LT), few suitable recipient parameters have been identified. To this end, we performed an in-depth analysis of hospitalization status and duration prior to LT as a potential risk factor for posttransplant outcome. The pretransplant hospitalization status of all patients undergoing LT between 2005 and 2016 at the Charité-Universitätsmedizin Berlin was analyzed retrospectively using propensity score matching. At the time of organ acceptance, 226 of 1134 (19.9%) recipients were hospitalized in an intensive care unit (ICU), 146 (12.9%) in a regular ward (RW) and 762 patients (67.2%) were at home. Hospitalized patients (RW and ICU) compared with patients from home showed a dramatically shorter 3-month survival (78.7% versus 94.4%), 1-year survival (66.3% versus 87.3%), and 3-year survival (61.7% versus 81.7%; all P 14 days, 60.5% versus 51.0%, P = 0.006). In conclusion, hospitalization status before transplantation is a valuable predictor of patient survival following LT