The evolution of extraordinary self-sacrifice

From a theoretical perspective, individuals are expected to sacrifice their welfare only when the benefits outweigh the costs. In nature, however, the costs of altruism and spite can be extreme, as in cases of irreversible sterility and self-destructive weaponry. Here we show that “extraordinary” self-sacrifice—in which actors pay costs that exceed the benefits they give or the costs they impose on recipients—can evolve in structured populations, where social actions bring secondary benefits to neighboring kin. When given information about dispersal, sedentary actors evolve extraordinary altruism towards dispersing kin. Likewise, when given information about dispersal and kinship, sedentary actors evolve extraordinary spite towards sedentary nonkin. Our results can thus be summed up by a simple rule: extraordinary self-sacrifice evolves when the actor’s neighbors are close kin and the recipient’s neighbors are not.

On the Estimation of the Initial Stock in the Problem of Resource Extraction

We consider a differential game of non-renewable resource extraction, in which the players do not know the precise value of the resource stock and, thus, have to make an estimate. We define the value of information about the initial stock and give recommendations for the choice of the estimate depending on the parameters of the problem. Further, we consider the situation where the players only know the bounds for the stock of the resource and solve the problem of computing the optimal estimate, such that it minimizes the players’ losses in the worst-case scenario. The analysis allows us to give a simple rule for the choice of the optimal estimate of the resource stock.

A Prediction Rule to Guide JAK2 Testing in Patients with Suspected Polycythemia Vera

Background: The widespread availability of molecular testing for JAK2 mutations has facilitated the diagnosis of polycythemia vera (PV) but also raises the concern of test overutilization in patients referred for elevated hemoglobin. At our institution, we have observed increased molecular testing in these patients with declining rates of JAK2 mutation positivity, suggesting that a prediction rule could be useful to guide such testing. In this study, we report the derivation and validation of a simple rule using complete blood count (CBC) parameters to predict the likelihood of having a JAK2 mutation in patients referred for elevated hemoglobin. Methods: We examined all patients with elevated hemoglobin (≥160 g/L for women, or ≥165 g/L for men), who underwent JAK2 mutation testing using the Next-Generation Sequencing (NGS)-based Oncomine Myeloid Research Assay (ThermoFisher Scientific, MA, USA), between 2018 and 2021 at the London Health Sciences Centre in Ontario, Canada. We extracted data including age and sex as well as CBC parameters at the time of testing, including hemoglobin, hematocrit, erythrocytes, leukocytes, neutrophils, platelets and mean corpuscular volume. All CBCs were performed on a Sysmex XN Analyzer (Sysmex Corporation, Japan). In the derivation cohort, JAK2-positive and -negative groups were compared using Student's t-tests or c 2 tests, as appropriate. We dichotomized potentially significant continuous variables at an optimal cut-off point using receiving operating characteristic curves. Potentially significant predictors were evaluated using multiple variable stepwise logistic regression analysis with JAK2 positivity as the dependent variable. The model was evaluated using Hosmer-Lemeshow tests and pseudo-R2 measures. A dichotomous score was derived based on the presence or absence of significant variables and subsequently evaluated and internally validated using logistic regression and c 2 tests using non-parametric bootstrapping with 1000 samples. The model was subsequently validated in the second cohort. Results: The derivation cohort included 308 patients tested between January 9, 2018 and December 19, 2019, and the validation cohort included 223 patients tested between January 7, 2020 and May 12, 2021. The characteristics of both cohorts are shown in Table 1. The final model included platelets above the upper quintile (308 × 10 9/L) and erythrocytes above the upper quartile (6.17 × 10 12/L) and a score of one was assigned to patients with either of these characteristics. The odds ratio for JAK2 positivity in patients with a score of 1 was 14.6 (95% CI 5.5-38.8) compared to those with a score of 0. The model had a sensitivity of 87.8% and a negative predictive value of 97.4% in the derivation cohort, and of 100% for both in the validation cohort. The percentage of JAK2 positive patients in patients with a score of 1 was 28%. The percent of false negatives was 2.6% (95% CI 1.1-6.0) and 0 (95% CI 0-2.8) in the derivation and validation cohorts, respectively. The use of this rule to guide molecular testing would have resulted in approximately 60% fewer tests. Conclusion: We developed and validated a simple rule to predict the likelihood of JAK2 mutation positivity in patients with a hemoglobin of 160 or higher, based on CBC parameters with a high negative predictive value (Figure 1). If implemented, this prediction rule could result in a significant reduction in molecular testing avoiding 60% or approximately 100 tests per year at our institution. This approach would be particularly beneficial for broader health system management of hematological malignancies, facilitating the reallocation of resources to emerging higher-yield molecular diagnostic investigation (Kawata et al., BJH 2021). Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Honesty and dishonesty in gossip strategies: a fitness interdependence analysis

Gossip, or sharing information about absent others, has been identified as an effective solution to free rider problems in situations with conflicting interests. Yet, the information transmitted via gossip can be biased, because gossipers may send dishonest information about others for personal gains. Such dishonest gossip makes reputation-based cooperation more difficult to evolve. But when are people likely to share honest or dishonest gossip? We build formal models to provide the theoretical foundation for individuals' gossip strategies, taking into account the gossiper's fitness interdependence with the receiver and the target. Our models across four different games suggest a very simple rule: when there is a perfect match (mismatch) between fitness interdependence and the effect of honest gossip, the gossiper should always be honest (dishonest); however, in the case of a partial match, the gossiper should make a choice based on their fitness interdependence with the receiver and the target and the marginal cost/benefit in terms of pay-off differences caused by possible choices of the receiver and the target in the game. Moreover, gossipers can use this simple rule to make optimal decisions even under noise. We discuss empirical examples that support the predictions of our model and potential extensions. This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’.

Use the best, ignore the rest: How heuristics allow to tell a lie from the truth

Could a simple rule of thumb help to find the truth? People struggle with integrating many putative cues to deception into an accurate veracity judgement. Heuristics simplify difficult decisions by ignoring most of the information and relying instead only on a few but highly diagnostic cues (’Use the best, ignore the rest’). We examined whether people would be able to tell lie from truth when instructed to make decisions based on a single, diagnostic cue (verifiability and richness in detail). We show that these simple judgements by lay people allowed to discriminate dishonest from honest statements. These judgements performed at or above state-of-the-art, resource-intensive content analysis by trained coders. For a tech- and training-free approach, heuristics were surprisingly accurate, and hold promise for practice.

On limits of contact tracing in epidemic control

Contact tracing and quarantine are well established non-pharmaceutical epidemic control tools. The paper aims to clarify the impact of these measures in evolution of epidemic. The proposed deterministic model defines a simple rule on the reproduction number R in terms of ratio of diagnosed cases and, quarantine and transmission parameters. The model is applied to the early stage of Covid19 crisis in Poland. We investigate 3 scenarios corresponding to different ratios of diagnosed cases. Our results show that, depending on the scenario, contact tracing prevented from 50% to over 90% of cases. The effects of quarantine are limited by fraction of undiagnosed cases. The key conclusion is that under realistic assumptions the epidemic can not be controlled without any social distancing measures.

Simple monetary rules: many strengths and few weaknesses

This paper endeavors to examine the basic idea in Richard Epstein’s book Simple Rules for a Complex World. It does so by considering a specific simple rule which was explicitly designed for complex world. A basic idea in Epstein’s book is that the more complex is the world the better is the case for simple rules. To show this, he develops six simple rules pertaining to the rights of individuals, first possession, contracts, torts, government eminent domain and the power of taxation to provide public goods. This paper considers one rule rather than six rules, and it looks at monetary policy rather than policy in general. While the context is different, the case for simple rules made here provides a useful comparison with the case made by Epstein.

Guest-occupiable space in the crystalline solid state: a simple rule-of-thumb for predicting occupancy

High-throughput analysis of the guest-occupiable space of nearly 40 000 solvates involving 20 different solvents yields a mean guest occupancy of 51.1(4)%.