Nash Prediction Research Articles

Associations of four surrogate insulin resistance indexes with non-alcoholic steatohepatitis in Chinese patients with obesity: a cross-sectional study.

This study was designed to evaluate the association of four surrogate indexes of IR with NASH in patients with obesity. A total of 270 patients who underwent bariatric surgery, were included in this cross-sectional study. NASH was diagnosed based on liver biopsies. Binary logistics regression analyses were performed to assess the associations of four surrogate indexes of IR (HOMA-IR, Matsuda index, TyG, and TG/HDL-C) with NASH in patients with obesity. The restricted cubic spline was used to assess the dose-response associations of surrogate indexes of IR with NASH after adjusting for confounding factors. NASH was diagnosed in 136 patients, with a prevalence of 50.37%. Compared with tertile 1, the fully adjusted ORs (95% CIs) of NASH for tertile 3 were 2.711(1.113-6.608) and 0.297 (0.152-0.579) for TyG and Matsuda index. Consistently, per SD increment of TyG were still significantly associated with 64% increased risks of NASH, and per SD increment of Matsuda index were still significantly associated with 38% decreased risks of NASH. In contrast, no significant associations were found between HOMA-IR and TG/HDL-C and the risk of NASH in patients with obesity (all P > 0.05). After adjusting covariates in restricted cubic splines, the risk of NASH decreased with the increment of Matsuda Index levels (P-nonlinear = 0.442, P-overall = 0.007) and with the decrement of TyG levels (P-nonlinear = 0.004, P-overall = 0.001). In patients with obesity, TyG and Matsuda index were independently related to the risk of NASH after adjustment for traditional risk factors. In addition, compared with HOMA-IR and TG/HDL-C, the Matsuda index and TyG may be more suitable for NASH prediction in patients with obesity.

Identification and analysis of significant genes in nonalcoholic steatohepatitis-hepatocellular carcinoma transformation: Bioinformatics analysis and machine learning approach

PurposeNonalcoholic steatohepatitis (NASH) has been an increasingly significant contributor to hepatocellular carcinoma (HCC). Understanding the progression from NASH to HCC is critical to early diagnosis and elucidating the underlying mechanisms. Results5 significant prognostic genes related to NASH-HCC transformation were identified through algorithm selection, which were ME1, TP53I3, SOCS2, GADD45G and CYP7A1. A diagnostic model for NASH prediction was established (AUC=0.988). TP53I3 and SOCS2 were selected as potential critical genes in the progression of NASH-HCC by external dataset validation and in vitro experiments on NASH and HCC cell lines. Immune infiltration analysis illustrated the correlation between 5 significant prognostic genes and immune cells. Single-cell analysis identified hepatocytes related to NASH-HCC transformation markers, revealing their promoting role in the transformation from NASH to HCC. ConclusionWith bulk-seq analysis and single-cell analysis, 5 significant prognostic genes related to NASH-HCC transformation were identified and validated at both dataset and in vitro experiment level. Among them, TP53I3 and SOCS2 might be potential critical genes in NASH-HCC progression. Single-cell analysis identified and revealed the critical role that NASH-HCC related hepatocytes play in NASH-HCC tansformation. Our research may introduce a new perspective to the diagnosis, treatment of NASH-related HCC.

How Do Game Design, Gender, and Players’ Backgrounds Affect Behavior in Framed Field Experiments? Evidence from Community Forestry in India

Framed field experiments (experimental games) are widely used to assess factors affecting cooperation in management of the commons. However, there is relatively little attention to how details of the games affect experimental results. This paper presents qualitative and quantitative results from a framed field experiment in which participants make decisions about extraction of a common-pool resource, a community forest. The experiment was conducted in 2017–2018 with 120 groups of resource users (split by gender) from 60 habitations in two Indian states, Andhra Pradesh and Rajasthan. We test whether within-subject treatments (non-communication, communication, and optional election of institutional arrangements (rules)), remuneration methods, and design of the game board affect harvest behavior and groups’ tendency to cooperate. We also examine how characteristics of the community and players affect players’ choices in the game, with special attention to gender differences. Results reveal participants harvested substantially less than the Nash prediction even in the absence of communication, with men extracting less than women in both states. For male groups in both states, both communication and optional rule election were associated with lower group harvest per round, as compared to the reference non-communication game. For female groups in both states communication itself did not significantly slow resource depletion; but introduction of optional rule election did reduce harvest amounts. For both men and women in Andhra Pradesh and men in Rajasthan, incentivized payments to individual participants significantly lowered group harvest, relative to community flat payment, suggesting such payments stimulated deliberation among game players. Findings have methodological and practical implications for designing behavioral intervention programs to improve common-pool resource governance.

Non-Steroidal Anti-Inflammatory Drugs and Risk of Acute Kidney Injury and Hyperkalemia in Older Adults: A Retrospective Cohort Study and External Validation of a Clinical Risk Model.

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used analgesics among older adults. Adverse effects may be avoided by careful patient selection. We aimed to evaluate the incidence of acute kidney injury (AKI) and/or hyperkalemia, risk factors, and the accuracy of an NSAID risk prediction model in a cohort of Asian older adults. We conducted a retrospective cohort study of older adults, age 65years and above, who received prescriptions between March 2015 and December 2017 from Singapore's largest cluster of public healthcare institutions. Factors associated with 30-day incident acute kidney injury and/or hyperkalemia were evaluated with multivariable regression analysis. Calibration and discrimination of the Nash prediction model were assessed using the Hosmer-Lemeshow goodness-of-fit test and C-statistic, respectively. The primary outcome occurred in 16.7% of 12,798 older adults. Topical NSAIDs (adjusted OR 1.29, 95% CI 1.15-1.45), systemic NSAIDs of 1-14 days' duration (adjusted OR 1.43, 95% CI 1.27-1.62), and systemic NSAIDs > 14 days (adjusted OR 1.84, 95% CI 1.37-2.49) were independently associated with the primary outcome, compared with no NSAID. Diabetes mellitus, cardiovascular disease, lower estimated glomerular filtration rate (eGFR), and diuretics were also independently associated with increased incident AKI and/or hyperkalemia. When applied to older adults with systemic NSAIDs > 14 days (n=305), the Nash risk model had poor calibration (p<0.001) and poor discrimination with C-statistic 0.527 (0.438, 0.616). Longer NSAID duration and systemic compared with topical route were associated with incremental odds for acute renal events. Further studies are required to improve the available risk model to guide NSAID prescriptions in older adults.

Focality and Asymmetry in Multi-Battle Contests

Abstract This article examines the influence of focality in Colonel Blotto games with a lottery contest success function (CSF), where the equilibrium is unique and in pure strategies. We hypothesise that the salience of battlefields affects strategic behaviour (the salient target hypothesis) and present a controlled test of this hypothesis against Nash predictions, checking the robustness of equilibrium play. When the sources of salience come from asymmetries in battlefield values or labels (as in Schelling, 1960), subjects over-allocate the resource to the salient battlefields relative to the Nash prediction. However, the effect is stronger with salient values. In the absence of salience, we find support for the Nash prediction.

Positional concerns and social network structure: An experiment

Abstract We experimentally study the positional concerns of individuals embedded in social networks. In the game, individuals compete for positional advantage with their direct neighbors by purchasing a positional good. The Nash equilibrium consumption is determined by the Katz-Bonacich centrality of the individual's network position, while the efficient outcome requires a lower consumption level. For most network positions, the gameplay converged to the Nash equilibrium, except for local centers that consumed less of the positional good than the Nash prediction. Despite this, the consumption of the positional good increased in the individual's centrality. The evolution of the gameplay was explained by the myopic best-response dynamics model.

A Rent Seeking Experiment with Leakage from the Contest Success Function

We contribute to the growing experimental literature on rent seeking contests that examines the effect of the prize structure on expenditures. We test the predictive power of a model (Godwin et al., 2006) that includes realistic features of actual political rent seeking contests that alter the contest success function. In this paper, we focus on a shift parameter in the contest success function, which Godwin et al. (2006) describe in a political context as policymaker costs. In practice, an increase in this shift parameter results in a decrease in the probability of a player winning the prize, ceteris paribus. The inclusion of this parameter makes it possible for no prize to be awarded in the contest. The model also allows for multiple prizes to be awarded, as well as the possibility of a single prize. Consistent with the existing literature on rent seeking, we find significant overspending relative to the Nash prediction. However, the inclusion of the probability shift parameter significantly reduces the amount of this overspending. Thus, the “policymaker cost” is associated with a reduction in the amount of inefficient rent dissipation; this result holds even after controlling for the level of competition and subject characteristics.

Mac-2 binding protein in non-alcoholic fatty liver disease: Is it a reliable diagnostic biomarker? A pilot study.

Aim of the studyThis study aimed to assess the level of serum Mac-2 binding protein (Mac-2BP) as a non-invasive biomarker for the diagnosis of non-alcoholic fatty liver disease (NAFLD).Material and methodsForty patients with NAFLD and 15 healthy sex- and age-matched subjects were included in this pilot study. Serum Mac-2BP level was measured using ELISA. Liver biopsy was taken from 20 patients.ResultsThere was no statistically significant difference between patients and controls regarding the level of Mac-2BP (p = 0.209). Mac-2BP had a statistically significant correlation with the grade of lobular inflammation (r = 0.464, p = 0.039). The Mac-2BP cut-off value used for NASH prediction was 9.55 µg/ml, with sensitivity and specificity of 100% and 91.7%, respectively.ConclusionsThis study showed that Mac-2BP is not elevated in NAFLD patients compared to controls. It also demonstrated that the reliability of Mac-2BP as a biomarker for NAFLD diagnosis is still controversial and needs more investigation.

Yes, I'll Do it: A Large-Scale Experiment on the Volunteer's Dilemma

In many real-life situations people face a simple decision whether to volunteer or not to provide some benefit for themselves and also for others. This research investigates the effects of the group size and the magnitude of the volunteering cost in a controlled large-scale laboratory experiment, where subjects play the volunteer’s dilemma only once. The experiment varies group sizes ranging from groups of 3 to about 100, and 2 different cost/benefit ratios. Results show that high cost reduces volunteering probability only in the smallest groups, but not for other group sizes. Furthermore, non-monotonic group size effect is found on the individual volunteering decisions. These findings are not in line with the mixed-strategy Nash equilibrium prediction. Subjects volunteer more often in most treatments than the Nash prediction which benefits them on average compared to the Nash prediction.

Focality and Asymmetry in Multi-Battle Contests

This article examines behavior in two-person constant-sum Colonel Blotto games in which each player maximizes the expected total value of the battlefields won. A lottery contest success function is employed in each battlefield. Recent experimental research on such games provides only partial support for Nash equilibrium behavior. We hypothesize that the salience of battlefields affects strategic behavior (the salient target hypothesis). We present a controlled test of this hypothesis – against Nash predictions – when the sources of salience come from certain asymmetries in either battlefield values or labels (as in Schelling 1960). In both cases, subjects over-allocate the resource to the salient battlefields relative to the Nash prediction. However, the effect is stronger with salient values. In the absence of salience, we replicate previous results in the literature supporting the Nash prediction.

Overbidding and overspreading in rent-seeking experiments: Cost structure and prize allocation rules

We study experimentally the effects of cost structure and prize allocation rules on the performance of rent-seeking contests. Most previous studies use a lottery prize rule and linear cost, and find both overbidding relative to the Nash equilibrium prediction and significant variation of efforts, which we term ‘overspreading.’ We investigate the effects of allocating the prize by a lottery versus sharing it proportionally, and of convex versus linear costs of effort, while holding fixed the Nash equilibrium prediction for effort. We find the share rule results in average effort closer to the Nash prediction, and lower variation of effort. Combining the share rule with a convex cost function further enhances these results. We can explain a significant amount of non-equilibrium behavior by features of the experimental design. These results contribute towards design guidelines for contests based on behavioral principles that take into account implementation features of a contest.

Overbidding and Overspreading in Rent-Seeking Experiments: Cost Structure and Prize Allocation Rules

We study experimentally the effects of cost structure and prize allocation rules on the performance of rent-seeking contests. Most previous studies use a lottery prize rule and linear cost, and find both overbidding relative to the Nash equilibrium prediction and significant variation of efforts, which we term ‘overspreading.’ We investigate the effects of allocating the prize by a lottery versus sharing it proportionally, and of convex versus linear costs of effort, while holding fixed the Nash equilibrium prediction for effort. We find the share rule results in average effort closer to the Nash prediction, and lower variation of effort. Combining the share rule with a convex cost function further enhances these results. We can explain a significant amount of non-equilibrium behavior by features of the experimental design. These results contribute towards design guidelines for contests based on behavioral principles that take into account implementation features of a contest.

INCOME REDISTRIBUTION AND PUBLIC GOOD PROVISION: AN EXPERIMENT

We experimentally investigate the impact of income redistribution on voluntary contributions by groups of four subjects. We compare equalizing and unequalizing redistribution. Our data are consistent with the neutrality theorem: Redistribution does not affect the amount of voluntarily provided public good at the group level. However, at the individual level, subjects tend to underadjust with respect to the Nash prediction. We also observe an insignificant adjustment asymmetry between the poor and the rich: Subjects who become poorer adjust their contribution by a larger absolute amount than subjects who become richer. Finally, poor subjects tend to overcontribute significantly more than rich subjects.

A CLEAR AND PRESENT MINORITY: HETEROGENEITY IN THE SOURCE OF ENDOWMENTS AND THE PROVISION OF PUBLIC GOODS

We conduct public goods experiments in which participant groups are heterogeneous in regards to the source of their endowments. We find that this dimension of heterogeneity significantly reduces contributions to the public good, yielding strong support for the Nash prediction of minimal contributions. These minimal contributions arise in environments in which there exists a clear minority in terms of source of endowments. We discuss these results in light of current research on the influence of heterogeneous populations on public goods provision and redistributive policies. (JEL C9, D63, H4, J15)

Asymmetry Spectrum of Cycle Amplitude in Rock-Paper-Scissor Game of Experimental Economics

In a finite population game, the strategy space should fall into a strategy lattice. In a stochastic evolutionary trajectory (Fig. 1), many cycles (generalized Shapley loop) could be filtered out (Table 1). The cycles associated with the stochastic process describe the time evolution. Referring to the direction of the path and the unit size of the lattice (Fig. 1), the amplitude of a cycle must be an integer. The cycles and their amplitudes and then the probability spectrum of the amplitude can be obtained.Data comes from Standard RPS population games. Subjects are random matching paired each round. 300 rounds are repeated in each of the 12 sessions in each treatment whose population size is 4, 6 and 8 respectively. In these games, Nash random and independent inference is the spectrum should be symmetry but Shapley inference is asymmetry.Results are (1) We provide, firstly, the spectrum of cycle amplitude (Fig. 2) from RPS population game; (2) Observed the spectrum is asymmetry (unbalance in /- amplitude and Tab. 2) rejects Nash prediction and supports Shapley prediction significant; (3) Interesting is that the characters of the observed spectrum consists with - the extended second law of thermodynamics - fluctuation theorems.In Summary, in the trajectories, even thought the cycles are erratic, but the distribution of the cycles amplitudes has its own regularity. With this finding, also supported from the observations in the experiments, we suggest that the so called erratic processes of the laboratory social evolution is intrinsic and obey fluctuation theorems.

Overdissipation and Convergence in Rent-Seeking Experiments: Cost Structure and Prize Allocation Rules

We study experimentally the effects of cost structure and prize allocation rules on the performance of rent-seeking contests. Most previous studies use a lottery prize rule and linear cost, and find both overdissipation relative to Nash equilibrium prediction and significant variation in individual subject efforts. In a 2 x 2 design, we investigate the effects of sharing the prize proportionally and of a convex cost function, while holding fixed the Nash equilibrium prediction for effort. We find that the share rule results in average effort closer to the Nash prediction, lower variation in individual efforts, and convergence of the distribution of individual efforts towards Nash over time. Combining the share rule with a convex cost function further enhances these results. Our findings indicate that a significant amount of subjects’ non-equilibrium behavior in contests can be explained by features of the experimental design. These results contribute towards design guidelines for contests based on behavioral principles that take into account contest features that may not affect the Nash equilibrium prediction. These lessons suggest design guidelines for future experiments on contests.

Public goods provision by asymmetric agents: experimental evidence

Economic theory predicts that individuals will free-ride, providing sub-optimal Nash equilibrium quantities of public goods. However, 25 years of experimental evidence indicates that individuals’ behavior often differs from the Nash prediction. This experiment examines provision in the context of asymmetric benefits and asymmetric costs of providing a public good with declining marginal benefits and increasing marginal costs. The design eliminates the coordination problem at the individual level inherent in previous declining marginal benefit experiments. Yet, even with the improved theoretical design, over-contribution persists, suggesting that it is a behavioral phenomenon rather than a design artifact. Analysis of individual contributions indicates that subjects’ responses to asymmetry match the theoretical prediction in 3 out of 4 single asymmetry cases. Thus, although over-contribution remains, the theoretical role of asymmetry is confirmed.

NON‐MONETARY INCENTIVES AND OPPORTUNISTIC BEHAVIOR: EVIDENCE FROM A LABORATORY PUBLIC GOOD GAME

This study reports data from a laboratory experiment that investigates the incentive effect of three distinct social communication schemes on free‐riding behavior. We use performance‐based approval and disapproval ratings and a linear public good game to address the above issues. The treatments vary in terms of subjects' opportunities to anonymously assign (1) only the approval ratings to other group members, (2) only the disapproval ratings to other group members, and (3) either the approval or the disapproval ratings to other group members (but not both to the same group member), after they play a standard linear public good game. Despite the Nash prediction of zero individual contribution in all three treatments, the data show that the disapproval points generate significantly higher contribution than the approval points. The treatment in which subjects could communicate either the approval or the disapproval points produces the highest level of contribution. We discuss the implications that these findings may have for efficient design of organizations. (JEL D03, H41, C72, C92)

English auctions with resale: An experimental study

I design and test a simple English auction and two English auctions with resale, but with different informational backgrounds. All three treatments theoretically have the same equilibrium. I find, however, that the possibility of resale alters behavior significantly. In the two treatments with resale, subjects deviated from both the Nash prediction and the common results about bidding behavior in English auctions. Subjects tend to overbid, when they are certain they can reap the whole surplus in the resale market. I employ different models like QRE and levels of reasoning and conclude that overbidding can be explained as a rational response to the noisy environment in markets with human participants, that is, as rational decision making when anticipating others to make errors. When the outcome of the resale market is not certain, there is significant signaling behavior and auction prices tend to be lower than the Nash prediction.

Erratum to: Varying the intensity of competition in a multiple prize rent seeking experiment

In Anderson and Freeborn (2009) we inadvertently made a coding error in estimating the effects of risk preferences on subjects’ rent seeking expenditures. In models 2 through 5 of Table 5, we include individual specific effects (gender and risk preference as measured by the midpoint of the coefficient of relative risk aversion, hereafter mid-CRRA) and state that we control for individual subject heterogeneity using fixed effects. Econometrically, we cannot include both fixed effects and gender/mid-CRRA; however, a coding error allowed us to generate the results we report. When we correctly account for individual heterogeneity using a random effects model, the coefficients on gender and mid-CRRA are not significant. However, when we follow Millner and Pratt (1991) by grouping individuals into risk preference categories and performing difference of means tests, there is a significant decrease in overspending relative to the Nash prediction as we move along the risk preference spectrum. Specifically, the four categories are risk loving (mid-CRRA 0.68). We are guided by Holt and Laury (2002) in separating subjects into the categories of somewhat risk averse and very risk averse. For risk loving individuals, the average deviation from the Nash prediction (calculated as observed effort minus Nash prediction) across all six scenarios is 262.22; for risk neutral, the average deviation is 256.97; for somewhat risk averse, the average deviation is 245.35; and for very risk averse subjects, the average deviation from the Nash prediction is 190.76. Table 1 displays