Keigo Inukai

Rejection of unfair offers in the ultimatum game is no evidence of strong reciprocity

The strong reciprocity model of the evolution of human cooperation has gained some acceptance, partly on the basis of support from experimental findings. The observation that unfair offers in the ultimatum game are frequently rejected constitutes an important piece of the experimental evidence for strong reciprocity. In the present study, we have challenged the idea that the rejection response in the ultimatum game provides evidence of the assumption held by strong reciprocity theorists that negative reciprocity observed in the ultimatum game is inseparably related to positive reciprocity as the two sides of a preference for fairness. The prediction of an inseparable relationship between positive and negative reciprocity was rejected on the basis of the results of a series of experiments that we conducted using the ultimatum game, the dictator game, the trust game, and the prisoner’s dilemma game. We did not find any correlation between the participants’ tendencies to reject unfair offers in the ultimatum game and their tendencies to exhibit various prosocial behaviors in the other games, including their inclinations to positively reciprocate in the trust game. The participants’ responses to postexperimental questions add support to the view that the rejection of unfair offers in the ultimatum game is a tacit strategy for avoiding the imposition of an inferior status.

Is consensus-seeking unique to humans? A selective review of animal group decision-making and its implications for (human) social psychology

Recent research on animal behavior suggests that group decision-making may not be uniquely human. Based on Tinbergen’s (1963) “four questions,” this paper proposes that linking biological- and social-science approaches is important to a better understanding of human group decisions. Toward this end, we first review some recent findings on collective behavior by social insects (ants and honeybees in particular). We then argue that several fundamental processes (e.g., positive feedback, nonlinear responses to social frequency information, and use of quorums) commonly underlie human and non-human group decision-making under uncertainty, while key prerequisites for the emergence of collective intelligence may be more vulnerable to social nuances in human contexts. We sketch some future research directions to promote cross-fertilizations between the two fields.

Rawlsian maximin rule operates as a common cognitive anchor in distributive justice and risky decisions

Significance Distributive justice is a highly controversial issue across many societies. Compared with the accumulation of various normative (“ought”) theories by philosophers over the centuries, our empirical (“is”) understanding of people’s distributive judgments remains insufficient. In a series of experiments, we show that the “maximin” concern (maximizing the minimum possible payoff) operates as a strong cognitive anchor in both distributive decisions for others and economic decisions for self, and that the right temporoparietal junction, associated with perspective taking, plays a key role in this linkage. Our approach illustrates how rigorous methods from behavioral, cognitive, and neural sciences can be combined to shed light on functional elements of distributive justice in our minds, and potential neural underpinnings shared by other nonsocial decisions. Distributive justice concerns the moral principles by which we seek to allocate resources fairly among diverse members of a society. Although the concept of fair allocation is one of the fundamental building blocks for societies, there is no clear consensus on how to achieve “socially just” allocations. Here, we examine neurocognitive commonalities of distributive judgments and risky decisions. We explore the hypothesis that people’s allocation decisions for others are closely related to economic decisions for oneself at behavioral, cognitive, and neural levels, via a concern about the minimum, worst-off position. In a series of experiments using attention-monitoring and brain-imaging techniques, we investigated this “maximin” concern (maximizing the minimum possible payoff) via responses in two seemingly disparate tasks: third-party distribution of rewards for others, and choosing gambles for self. The experiments revealed three robust results: (i) participants’ distributive choices closely matched their risk preferences—“Rawlsians,” who maximized the worst-off position in distributions for others, avoided riskier gambles for themselves, whereas “utilitarians,” who favored the largest-total distributions, preferred riskier but more profitable gambles; (ii) across such individual choice preferences, however, participants generally showed the greatest spontaneous attention to information about the worst possible outcomes in both tasks; and (iii) this robust concern about the minimum outcomes was correlated with activation of the right temporoparietal junction (RTPJ), the region associated with perspective taking. The results provide convergent evidence that social distribution for others is psychologically linked to risky decision making for self, drawing on common cognitive–neural processes with spontaneous perspective taking of the worst-off position.

Reinforcement learning accounts for moody conditional cooperation behavior: experimental results.

In social dilemma games, human participants often show conditional cooperation (CC) behavior or its variant called moody conditional cooperation (MCC), with which they basically tend to cooperate when many other peers have previously cooperated. Recent computational studies showed that CC and MCC behavioral patterns could be explained by reinforcement learning. In the present study, we use a repeated multiplayer prisoner’s dilemma game and the repeated public goods game played by human participants to examine whether MCC is observed across different types of game and the possibility that reinforcement learning explains observed behavior. We observed MCC behavior in both games, but the MCC that we observed was different from that observed in the past experiments. In the present study, whether or not a focal participant cooperated previously affected the overall level of cooperation, instead of changing the tendency of cooperation in response to cooperation of other participants in the previous time step. We found that, across different conditions, reinforcement learning models were approximately as accurate as a MCC model in describing the experimental results. Consistent with the previous computational studies, the present results suggest that reinforcement learning may be a major proximate mechanism governing MCC behavior.

Decision Under Ambiguity: Effects of Sign and Magnitude

Decision under ambiguity (uncertainty with unknown probabilities) has been attracting attention in behavioral and neuroeconomics. However, recent neuroimaging studies have mainly focused on gain domains while little attention has been paid to the magnitudes of outcomes. In this study, we examined the effects of the sign (i.e., gain and loss) and magnitude of outcomes on ambiguity aversion and the additivity of subjective probabilities in Ellsbergs urn problem. We observed that (i) ambiguity aversion was observed in both signs, and (ii) subadditivity of subjective probability was not observed in negative outcomes.

Empathizing With a Dissimilar Other The Role of Self–Other Distinction in Sympathetic Responding

Can we empathize effectively with someone who has a different sensitivity to physical events from ours? Or, are we susceptible to an egocentric bias in overprojection, which may lead us to under- or overreact in such cases? In this study, participants with normal visual and auditory capacity observed a video clip in which a sighted or blind target was exposed to a strong flash or high-frequency sound, while their physiological arousals during the observation were recorded. On average, participants displayed a differential arousal pattern to the aversive stimuli, according to the target’s ability to perceive them. Degrees of arousal control were also correlated with dispositional differences in empathy. Participants who scored higher on the Empathic Concern subscale of Davis’s Interpersonal Reactivity Index were better at controlling arousals in accordance with the Target × Stimulus interaction. The authors’ findings have important implications for helping disabled people while respecting their inherent dignity and individual autonomy.

Implications from Biased Probability Judgments for International Disparities in Momentum Returns

ABSTRACT Momentum is a consistent phenomenon in financial data from the majority of markets around the globe. One prominent exception is the Japanese market, where returns from a momentum-investment strategy are nonexistent. The authors investigated international differences in the representativeness heuristic, which is one potential driver of momentum. After observing sequences of a random walk, subjects give probability estimates for the direction of the respective next change. The experiment was conducted in Japan and in Germany. For a subgroup of participants with lower cognitive abilities our results are perfectly in line with international momentum evidence.

History of Cooperation: A Positive Analysis of the Overlapping Mechanism

Given that cooperation can lead to a large cost for an individual there must be some social mechanisms maintaining this behavior. Recently, some economists have used game theory to provide a theoretical understanding of the mechanisms at play. For instance using the overlapping generation game, it has been shown that rewards and penalties given in the past and those perceived to occur in the future has a large influence on the players willingness to cooperate. However while these mathematical arguments are persuasive whether such equilibrium exists in the real world requires empirical observation. To date there are some empirical evidence focused on case studies but these tend to lack enough information to validate the theory. Therefore our objective is to provide evidence for the theory that the overlapping mechanism influences cooperative behavior by using the overlapping generation game in economic experiments. We would like to show how the path of the equilibrium is affected by the history of previous subject’s choices through comparing a game with and without an overlapping mechanism.