Deciding for others as a neutral party recruits risk-neutral perspective-taking: Model-based behavioral and fMRI experiments.

Risky decision making for others is ubiquitous in our societies. Whereas financial decision making for oneself induces strong concern about the worst outcome (maximin concern) as well as the expected value, behavioral and neural characteristics of decision making for others are less well understood. We conducted behavioral and functional magnetic resonance imaging (fMRI) experiments to examine the neurocognitive underpinnings of risky decisions for an anonymous other, using decisions for self as a benchmark. We show that, although the maximin concern affected both types of decisions equally strongly, decision making for others recruited a more risk-neutral computational mechanism than decision making for self. Specifically, participants exhibited more balanced information search when choosing a risky option for others. Activity of right temporoparietal junction (rTPJ, associated with cognitive perspective taking) was parametrically modulated by options' expected values in decisions for others, and by the minimum amounts in decisions for self. Furthermore, individual differences in self-reported empathic concern modified these attentional and neural processes. Overall, these results indicate that the typical maximin concern is attenuated in a risk-neutral direction in decisions for others as compared to self. We conjecture that, given others' diverse preferences, deciding as a neutral party may cognitively recruit such risk-neutrality.

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.

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

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.

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.

Stress hormones predict hyperbolic time-discount rates six months later in adults.

OBJECTIVES: Stress hormones have been associated with temporal discounting. Although time-discount rate is shown to be stable over a long term, no study to date examines whether individual differences in stress hormones could predict individuals' time-discount rates in the relatively distant future (e.g., six month later), which is of interest in neuroeconomics of stress-addiction association. METHODS: We assessed 87 participants' salivary stress hormone (cortisol, cortisone, and alpha-amylase) levels and hyperbolic discounting of delayed rewards consisting of three magnitudes, at the time-interval of six months. For salivary steroid assays, we employed a liquid chromatography/ mass spectroscopy (LC/MS) method. The correlations between the stress hormone levels and time-discount rates were examined. RESULTS: We observed that salivary alpha-amylase (sAA) levels were negatively associated with time-discount rates in never-smokers. Notably, salivary levels of stress steroids (i.e., cortisol and cortisone) negatively and positively related to time-discount rates in men and women, respectively, in never-smokers. Ever-smokers' discount rates were not predicted from these stress hormone levels. CONCLUSIONS: Individual differences in stress hormone levels predict impulsivity in temporal discounting in the future. There are sex differences in the effect of stress steroids on temporal discounting; while there was no sex defference in the relationship between sAA and temporal discounting.

[Accuracy of judgment about others' cooperative behavior: effects of attractiveness and facial expressiveness].

Cooperation in interdependent relationships is based on reciprocity in repeated interactions. However, cooperation in one-shot relationships cannot be explained by reciprocity. Frank, Gilovich, & Regan (1993) argued that cooperative behavior in one-shot interactions can be adaptive if cooperators displayed particular signals and people were able to distinguish cooperators from non-cooperators by decoding these signals. We argue that attractiveness and facial expressiveness are signals of cooperators. We conducted an experiment to examine if these signals influence the detection accuracy of cooperative behavior. Our participants (blind to the target's behavior in a Trust Game) viewed 30-seconds video-clips. Each video-clip was comprised of a cooperator and a non-cooperator in a Trust Game. The participants judged which one of the pair gave more money to the other participant. We found that participants were able to detect cooperators with a higher accuracy than chance. Furthermore, participants rated male non-cooperators as more attractive than male cooperators, and rated cooperators more expressive than non-cooperators. Further analyses showed that attractiveness inhibited detection accuracy while facial expressiveness fostered it.

Salivary testosterone levels and autism-spectrum quotient in adults.

OBJECTIVES: The purpose of this study is to examine the relationship between salivary testosterone levels and autistic traits in adults. METHODS: A total of 92 male and female adults participated in the present study. Their salivary testosterone level (T) and score of Japanese version of Autism-spectrum Quotient (AQ) were assessed to examine the relationship between salivary testosterone level and autistic traits in adults. RESULTS: We observed a positive correlation between T and AQ in a group of both sexes. The correlation disappeared when we conducted correlation analysis by sex. However, although there was no sex difference in the score of the subscale of attention switching, attention switching was related to T. CONCLUSIONS: Although the relationship between T and AQ may mainly result from sex differences, the subscale of attention switching may be modulated by testosterone.

Salivary alpha-amylase levels and big five personality factors in adults.

OBJECTIVES: Salivary alpha-amylase (sAA) has been utilized as a non-invasive measure of sympathoadrenal medullary (SAM) activation. Little is known regarding the relationship between personality inventories and baseline sAA. This study was designed to examine the relationships between the scores of big five inventory (BFI) factors, age, and sAA in adults (aged twenty to seventy years old). METHODS: We assessed 97 participants' BFI scores and sAA. The correlations between the BFI factor scores and sAA were examined. RESULTS: We observed (1) a positive correlation between Neuroticism and sAA, and a negative correlation between Agreeableness and sAA and (2) a positive correlation between age and sAA. These correlations between BFI scores and sAA remained significant after controlling for age. After controlling for age, all BFI factors except Conscientiousness were related to sAA. CONCLUSIONS: Subjects with high Neuroticism and low Extraversion, Agreeableness and Openness may have high sAA. sAA has been demonstrated to be useful for examining the relationship between adrenergic activity and personality, in a non-invasive manner.

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 Ellsberg's 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.

Distinct neuropsychological processes may mediate decision-making under uncertainty with known and unknown probability in gain and loss frames.

Decision-making under uncertainty has been studied in psychiatry, economic psychology, and neuroeconomics. Psychiatric patients (e.g., drug addicts) often show low degrees of aversion to potential danger. Investigation into neuropsychological processing underlying decision under uncertainty is important for medical treatments of neuropsychiatric disorders. In economic decision theory, choices under uncertainty with and without known probabilities of outcomes have been discriminated. Regarding decision-making under uncertainty with known probabilities (risk), Kahnemann-Tversky's prospect theory revealed that people tend to avoid uncertainty in potential gains (i.e., risk-aversion in a gain-frame); on the contrary, prefer uncertainty in potential losses (i.e., risk-seeking in a loss-frame). Regarding choices between possible gains with known and unknown probabilities, Ellsberg demonstrated that, in a gain-frame, people tend to avoid uncertainty with unknown probabilities, more dramatically than uncertainty with known probabilities. This can be explained by risk/uncertainty aversion in the gain-frame, suggesting that uncertainty with known and unknown probabilities (i.e., risk and Knightian uncertainty, respectively) may possibly be processed by similar neuropsychological processing in the gain-frame. However, in spite of accumulating evidence in neuroimaging and neuroeconomic studies, it is still unknown whether probability and Knightian uncertainty in the loss-frame are mediated by similar neuropsychological processes as well. We propose that distinct neuropsychological processes may mediate potential losses with known and unknown probabilities, based on recent findings in neuroeconomics and our experiment. Importance of examining subjects' degree of Knightian uncertainty aversion for the prediction/treatment of drug addicts' risky behavior (e.g., needle-sharing) is also discussed.