When it comes to experiments with multiple-round decisions under risk, the current payoff mechanisms are incentive compatible with either outcome weighting theories or probability weighting theories, but not both. In this paper, I introduce a new payoff mechanism, the Accumulative Best Choice (“ABC”) mechanism that is incentive compatible for all rational risk preferences. I also identify three necessary and sufficient conditions for a payoff mechanism to be incentive compatible for all models of decision under risk with complete and transitive preferences. I show that ABC is the unique incentive compatible mechanism for rational risk preferences in a multiple-task setting. In addition, I test empirical validity of the ABC mechanism in the lab. The results from both a choice pattern experiment and a preference (structural) estimation experiment show that individual choices under the ABC mechanism are statistically not different from those observed with the one-round task experimental design. The ABC mechanism supports unbiased elicitation of both outcome and probability transformations as well as testing alternative decision models that do or do not include the independence axiom.

A vast amount of empirical and theoretical research on public good games indicates that the threat of punishment can curb free-riding in human groups engaged in joint enterprises. Since punishment is often costly, however, this raises an issue of second-order free-riding: indeed, the sanctioning system itself is a common good which can be exploited. Most investigations, so far, considered peer punishment: players could impose fines on those who exploited them, at a cost to themselves. Only a minority considered so-called pool punishment. In this scenario, players contribute to a punishment pool before engaging in the joint enterprise, and without knowing who the free-riders will be. Theoretical investigations (Sigmund et al., Nature 466:861–863, 2010) have shown that peer punishment is more efficient, but pool punishment more stable. Social learning, i.e., the preferential imitation of successful strategies, should lead to pool punishment if sanctions are also imposed on second-order free-riders, but to peer punishment if they are not. Here we describe an economic experiment (the Mutual Aid game) which tests this prediction. We find that pool punishment only emerges if second-order free riders are punished, but that peer punishment is more stable than expected. Basically, our experiment shows that social learning can lead to a spontaneously emerging social contract, based on a sanctioning institution to overcome the free rider problem.

In this essay, I point out that the age-limit norm is misrepresented and misperceived in current analyses of leadership changes in the Chinese Communist Party for two reasons. First, the method employed in these analyses fails to capture the complexity of the rules that constitute the norm. Second, the method is ill-equipped to reflect the stratification of power at the top of the Party. To rectify these issues, I provide a structured framework to examine the age distribution patterns of membership changes at national Party congresses. I conclude that the age-limit norm functions as a nondemocratic mechanism for the Party and its top leaders to facilitate the exit of current powerholders and redistribute power en masse in a peaceful manner with reduced cost, enhanced transparency, and reasonable credibility. The framework I offer can help reveal the hidden significance and resilience of the age-limit norm, which has thus far been overlooked, obscured, or underestimated in current analyses.

We demonstrate how the standard usage of the random incentive system in ambiguity experiments eliciting certainty and probability equivalents might not be incentive compatible if the decision-maker is ambiguity averse. We propose a slight modification of the procedure in which the randomization takes place before decisions are made and the state is realized, and prove that if subjects evaluate the experimental environment in that way (first-risk, second-uncertainty), incentive compatibility may be restored.

Two-dimensional gaseous detonations near critical propagation state were studied numerically in a channel with stoichiometric H$_2$/air and H$_2$/O$_2$ mixtures. Detonation waves exhibit a mode-locking effect (MLE) in a single-headed mode regime. Increasing the channel width alters the strength and propagation period of the single transverse wave. This leads to MLE failure and the occurrence of the single-dual-headed critical mode, featuring the emergence of a new transverse wave. For a stoichiometric H$_2$/air mixture, generation of the new transverse wave is due to interactions between the detonation front and the local explosion wave originating from interactions between the transverse wave and unreacted gas pocket downstream. Whereas, for a stoichiometric H$_2$/O$_2$ mixture, a transverse wave interacting with the wall produces Mach reflection bifurcation, causing MLE failure and generation of the new transverse wave. Our results show that all transverse waves manifest as strong transverse wave (STW) structures, with most belonging to the second kind, and an acoustic coupling exists between the typical second kind of STW structure and the acoustic wave in the induction zone behind the Chapman–Jouguet detonation front. A high-pressure region close to the STW structure plays a crucial role in exploring the transverse dynamics of this structure. Shock polars with rational assumptions are adopted to predict flow states in this region. The roles of pivotal factors in influencing the flow states and wave structure are clarified, and characteristic pressure values derived adequately represent the STW structure’s transverse dynamic behaviours. Lastly, the relationship between the kinematics and kinds of STW structures is unveiled.

Decisions to trust in strategic situations involve ambiguity (unknown probabilities). Despite many theoretical studies on ambiguity in game theory, empirical studies have lagged behind due to a lack of measurement methods, where separating ambiguity attitudes from beliefs is crucial. Baillon et al. (Econometrica, 2018b) introduced a method that allows for such a separation for individual choice. We extend this method to strategic situations and apply it to the trust game, providing new insights. People’s ambiguity attitudes and beliefs both matter for their trust decisions. People who are more ambiguity averse decide to trust less, and people with more optimistic beliefs about others’ trustworthiness decide to trust more. However, people who are more a-insensitive (insufficient discrimination between different likelihood levels) are less likely to act upon their beliefs. Our measurement of beliefs, free from contamination by ambiguity attitudes, shows that traditional introspective trust survey measures capture trust in the commonly accepted sense of belief in trustworthiness of others. Further, trustworthy people also decide to trust more due to their beliefs that others are similar to themselves. This paper shows that applications of ambiguity theories to game theory can bring useful new empirical insights.

Previous studies have suggested that negative emotion can enhance memory accuracy. However, they were not conducted in the context of social interactions using the methodology of experimental economics. Based on the present study, we find that in such a context, individuals’ memory recall accuracy depends on the kindness of acts and who performed them, and negative emotion may lower memory accuracy. A victim of an unkind act is more likely to forget than someone who benefited from a kind act. This result supports the hypothesis that individuals may strategically manipulate their memory by forgetting an unpleasant experience. We also find that individuals who committed an unkind act tend to perceive it as less unkind as time moves on. They also tend to believe that a higher percentage of players have also committed the unkind act. Overall, the results support the hypothesis that individuals strategically manipulate their memory and beliefs to maintain self-esteem or feel less guilty.

In this paper, we complete the proof of the conjecture of Gross and Zagier concerning algebraicity of higher Green functions at a single CM point on the product of modular curves. The new ingredient is an analogue of the incoherent Eisenstein series over a real quadratic field, which is constructed as the Doi-Naganuma theta lift of a deformed theta integral on hyperbolic 1-space.

While both simultaneous and sequential contests are mechanisms used in practice such as crowdsourcing, job interviews and sports contests, few studies have directly compared their performance. By modeling contests as incomplete information all-pay auctions with linear costs, we analytically and experimentally show that the expected maximum effort is higher in simultaneous contests, in which contestants choose their effort levels independently and simultaneously, than in sequential contests, in which late entrants make their effort choices after observing all prior participants’ choices. Our experimental results also show that efficiency is higher in simultaneous contests than in sequential ones. Sequential contests’ efficiency drops significantly as the number of contestants increases. We also discover that when participants’ ability follows a power distribution, high ability players facing multiple opponents in simultaneous contests tend to under-exert effort, compared to theoretical predictions. We explain this observation using a simple model of overconfidence.

In this study we conduct a lab-in-the-field experiment with low-income Hispanics in three neighborhoods in a large city in the U.S. to investigate how identity and social exclusion influences individual contributions to fund local public goods. We find that while the strength of identity has a significant and positive impact on individual contributions to local public goods, the perception of social exclusion significantly decreases contributions. Our findings thus suggest factors that may impede full civic participation, and shed important light on potential policies to increase integration of immigrants and ethnic minorities into mainstream society.

Sepiolite is considered a suitable substrate for Maya blue pigment. However, the interaction between sepiolite and indigo dye has not been fully understood. Previous studies have demonstrated that pre-treatment of sepiolite by heating or acid was useful in identifying the sepiolite–indigo interaction. The purpose of the present study was to prepare a series of hybrid sepiolite–indigo pigments after modifying the sepiolite using various alkali treatments (NaOH), then to evaluate their properties with respect to color, chemical resistance, and photostability. Samples were characterized using reflectance spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, and N2 adsorption-desorption. Under alkaline conditions, Si4+ and Mg2+ ions in sepiolite partially dissolved, disrupting the coordinated water associated with them. Mg2+ ions precipitated and blocked the structural channels of the sepiolite. The impact of the alkali treatment on the microporous structure and coordinated water of sepiolite significantly influenced the color properties and stability of the hybrid pigments. Proper alkaline treatment enhanced the greenish hue and chemical stability of the pigment, while severe treatments apparently compromised the structural integrity of the sepiolite, thus diminishing the quality of the hybrid pigment. Results from this study provide new insights into the color-causing and stabilizing mechanisms of sepiolite-based Maya blue pigment and also provide guidance for developing hybrid pigments based on clay minerals and organic dyes.

The dynamics of small-scale structures in free-surface turbulence is crucial to large-scale phenomena in natural and industrial environments. Here, we conduct experiments on the quasi-flat free surface of a zero-mean-flow turbulent water tank over the Reynolds number range $Re_{\lambda } = 207$–312. By seeding microscopic floating particles at high concentrations, the fine scales of the flow and the velocity-gradient tensor are resolved. A kinematic relation is derived expressing the contribution of surface divergence and vorticity to the dissipation rate. The probability density functions of divergence, vorticity and strain rate collapse once normalised by the Kolmogorov scales. Their magnitude displays strong intermittency and follows chi-square distributions with power-law tails at small values. The topology of high-intensity events and two-point statistics indicate that the surface divergence is characterised by dissipative spatial and temporal scales, while the high-vorticity and high-strain-rate regions are larger, long-lived, concurrent and elongated. The second-order velocity structure functions obey the classic Kolmogorov scaling in the inertial range when the dissipation rate on the surface is considered, with a different numerical constant than in three-dimensional turbulence. The cross-correlation among divergence, vorticity and strain rate indicates that the surface-attached vortices are strengthened during downwellings and diffuse when those dissipate. Sources (sinks) in the surface velocity fields are associated with strong (weak) surface-parallel stretching and compression along perpendicular directions. The floating particles cluster over spatial and temporal scales larger than those of the sinks. These results demonstrate that, compared with three-dimensional turbulence, in free-surface turbulence the energetic scales leave a stronger imprint on the small-scale quantities.

The ability to understand and speak more than one language (i.e., bilingualism) may provide benefits to preserving social cognition against normal age-related deteriorations. This study examined how variations in bilingual language experience influence theory-of-mind (ToM) understanding in late adulthood. One hundred and five cognitively healthy older adults (Mage = 66.23 years, range = 56–79) and 80 young adults (Mage = 22.03 years, range = 19–30), who were bilingual speakers, completed a ToM task battery, a self-report questionnaire on their language background, and a battery of general cognition assessments. We found an overall age-related decline in ToM, where older adults made more errors in inferring others’ mental states compared with young adults. Importantly, an earlier L2 age of acquisition (L2AoA) predicted better ToM performance among older adults, over and above the effects of age, education, and general cognition. The results suggest that early bilingual acquisition may enhance social cognitive processes during development and contribute to intact ToM abilities in older adult bilinguals.