Overlapping and distinct representations of advantageous and disadvantageous inequality

Brain responses to self- and other- unfairness under resource distribution context: Meta-analysis of fMRI studies

Under resource distribution context, individuals have a strong aversion to unfair treatment not only toward themselves but also toward others. However, there is no clear consensus regarding the commonality and distinction between these two types of unfairness. Moreover, many neuroimaging studies have investigated how people evaluate and respond to unfairness in the abovementioned two contexts, but the consistency of the results remains to be investigated. To resolve these two issues, we sought to summarize existing findings regarding unfairness to self and others and to further elucidate the neural underpinnings related to distinguishing evaluation and response processes through meta-analyses of previous neuroimaging studies. Our results indicated that both types of unfairness consistently activate the affective and conflict-related anterior insula (AI) and dorsal anterior cingulate cortex/supplementary motor area (dACC/SMA), but the activations related to unfairness to self appeared stronger than those related to others, suggesting that individuals had negative reactions to both unfairness and a greater aversive response toward unfairness to self. During the evaluation process, unfairness to self activated the bilateral AI, dACC, and right dorsolateral prefrontal cortex (DLPFC), regions associated with unfairness aversion, conflict, and cognitive control, indicating reactive, emotional and automatic responses. In contrast, unfairness to others activated areas associated with theory of mind, the inferior parietal lobule and temporoparietal junction (IPL-TPJ), suggesting that making rational judgments from the perspective of others was needed. During the response, unfairness to self activated the affective-related left AI and striatum, whereas unfairness to others activated cognitive control areas, the left DLPFC and the thalamus. This indicated that the former maintained the traits of automaticity and emotionality, whereas the latter necessitated cognitive control. These findings provide a fine-grained description of the common and distinct neurocognitive mechanisms underlying unfairness to self and unfairness to others. Overall, this study not only validates the inequity aversion model but also provides direct evidence of neural mechanisms for neurobiological models of fairness.

Acute stress during witnessing injustice shifts third-party interventions from punishing the perpetrator to helping the victim

People tend to intervene in others' injustices by either punishing the transgressor or helping the victim. Injustice events often occur under stressful circumstances. However, how acute stress affects a third party's intervention in injustice events remains open. Here, we show a stress-induced shift in third parties' willingness to engage in help instead of punishment by acting on emotional salience and central-executive and theory-of-mind networks. Acute stress decreased the third party's willingness to punish the violator and the severity of the punishment and increased their willingness to help the victim. Computational modeling revealed a shift in preference of justice recovery from punishment the offender toward help the victim under stress. This finding is consistent with the increased dorsolateral prefrontal engagement observed with higher amygdala activity and greater connectivity with the ventromedial prefrontal cortex in the stress group. A brain connectivity theory-of-mind network predicted stress-induced justice recovery in punishment. Our findings suggest a neurocomputational mechanism of how acute stress reshapes third parties' decisions by reallocating neural resources in emotional, executive, and mentalizing networks to inhibit punishment bias and decrease punishment severity.

Unraveling how the third-party brain under stress responds to injustices

How third-party individuals respond to injustices is important for resolving conflict in society. A study in PLOS Biology shows that individuals experiencing acute stress prefer to aid victims over punishing offenders, an opposite pattern to non-stress conditions.

Same allocation proposed by an individual or a group elicits distinct responses: Evidence from event-related potentials and neural oscillation

People tend to perceive the same information differently depending on whether it is expressed in an individual or a group frame. It has also been found that the individual (vs. group) frame of expression tends to lead to more charitable giving and greater tolerance of wealth inequality. However, little is known about whether the same resource allocation in social interactions elicits distinct responses depending on proposer type. Using the second-party punishment task, this study examined whether the same allocation from different proposers (individual vs. group) leads to differences in recipient behavior and the neural mechanisms. Behavioral results showed that reaction times were longer in the unfair (vs. fair) condition, and this difference was more pronounced when the proposer was the individual (vs. group). Neural results showed that proposer type (individual vs. group) influenced early automatic processing (indicated by AN1, P2, and central alpha band), middle processing (indicated by MFN and right frontal theta band), and late elaborative processing (indicated by P3 and parietal alpha band) of fairness in resource allocation. These results revealed more attentional resources were captured by the group proposer in the early stage of fairness processing, and more cognitive resources were consumed by processing group-proposed unfair allocations in the late stage, possibly because group proposers are less identifiable than individual proposers. The findings provide behavioral and neural evidence for the effects of "individual/group" framing leading to cognitive differences. They also deliver insights into social governance issues, such as punishing individual and/or group violations.

Abstract concepts and simulated competition

To better understand the social determinants of conceptual knowledge we devised a task in which participants were asked to judge the match between a definition (expressed in abstract or concrete terms) and a target-word (also either abstract or concrete). The task was presented in the form of a competition that could/could not include an opponent, and in which different percentages of response rounds were assigned to the participant at the experimenter's discretion. Thus, depending on the condition, participants were either exposed to a competitive context mimicking a privileged/unprivileged interaction with the experimenter or to a socially neutral setting. Results showed that manipulation of the social context selectively affected judgments on abstract stimuli: responses were significantly slower whenever a definition and/or a target word were presented in abstract form and when participants were in the favorable condition of responding in most of the trials. Moreover, only when processing abstract material, responses were slower when an opponent was expected to be present. Data are discussed in the frame of the different cognitive engagements involved when treating abstract and concrete concepts as well as in relation to the possible motivational factors prompted by the experimental set-up. The role of social context as a crucial element for abstract knowledge processing is also considered.

A unified neural account of contextual and individual differences in altruism

Altruism is critical for cooperation and productivity in human societies but is known to vary strongly across contexts and individuals. The origin of these differences is largely unknown, but may in principle reflect variations in different neurocognitive processes that temporally unfold during altruistic decision making (ranging from initial perceptual processing via value computations to final integrative choice mechanisms). Here, we elucidate the neural origins of individual and contextual differences in altruism by examining altruistic choices in different inequality contexts with computational modeling and electroencephalography (EEG). Our results show that across all contexts and individuals, wealth distribution choices recruit a similar late decision process evident in model-predicted evidence accumulation signals over parietal regions. Contextual and individual differences in behavior related instead to initial processing of stimulus-locked inequality-related value information in centroparietal and centrofrontal sensors, as well as to gamma-band synchronization of these value-related signals with parietal response-locked evidence-accumulation signals. Our findings suggest separable biological bases for individual and contextual differences in altruism that relate to differences in the initial processing of choice-relevant information.

Neurocomputational evidence that conflicting prosocial motives guide distributive justice

In the history of humanity, most conflicts within and between societies have originated from perceived inequality in resource distribution. How humans achieve and maintain distributive justice has therefore been an intensely studied issue. However, most research on the corresponding psychological processes has focused on inequality aversion and has been largely agnostic of other motives that may either align or oppose this behavioral tendency. Here we provide behavioral, computational, and neuroimaging evidence that distribution decisions are guided by three distinct motives-inequality aversion, harm aversion, and rank reversal aversion-that interact with each other and can also deter individuals from pursuing equality. At the neural level, we show that these three motives are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior. Our findings provide a comprehensive framework for understanding the cognitive and biological processes by which multiple prosocial motives are coordinated in the brain to guide redistribution behaviors. This framework enhances our understanding of the brain mechanisms underlying equality-related behavior, suggests possible neural origins of individual differences in social preferences, and provides a new pathway to understand the cognitive and neural basis of clinical disorders with impaired social functions.

The impact of employee compensation restrictions on labor productivity in state-owned enterprises: Evidence from China

Employees are important stakeholders in an organization. This paper aims to examine the effectiveness of limits on employee compensation in state-owned enterprises (SOEs), a policy for employees of state-owned enterprises issued by the China State-owned Assets Supervision and Administration Commission (SASAC) in 2010. Employing a difference-in-differences analysis for a sample of Chinese listed companies from 2007 to 2013, the results show that employee compensation restriction enhances the labor productivity of SOEs. This policy effect is mainly due to the contribution of compensation limits to the external fairness of employee compensation, and the findings remain unchanged after a series of robustness testing procedures. In addition, the employee compensation restriction policy significantly affects labor productivity improvement in monopolistic industries or mature SOEs.

Observing others give & take: A computational account of bystanders' feelings and actions

Social interactions influence people's feelings and behavior. Here, we propose that a person's well-being is influenced not only by interactions they experience themselves, but also by those they observe. In particular, we test and quantify the influence of observed selfishness and observed inequality on a bystanders' feelings and non-costly punishment decisions. We developed computational models that relate others' (un)selfish acts to observers' emotional reactions and punishment decisions. These characterize the rules by which others' interactions are transformed into bystanders' reactions, and successfully predict those reactions in out-of-sample participants. The models highlight the impact of two social values-'selfishness aversion' and 'inequality aversion'. As for the latter we find that even small violations from perfect equality have a disproportionately large impact on feelings and punishment. In this age of internet and social media we constantly observe others' online interactions, in addition to in-person interactions. Quantifying the consequences of such observations is important for predicting their impact on society.

Neural mechanisms of the mood effects on third‐party responses to injustice after unfair experiences

Behavioral decision theory argues that humans can adjust their third‐party responses (e.g., punishment and compensation) to injustice by integrating unfair experiences. Typically, the mood plays an important role in such a decision‐making process. However, the underlying neurocognitive bases remain largely unclear. We first employ a modified third‐party justice game in which an allocator split an amount of money between oneself and a receiver. The participants can reapportion the money as observers by choosing from the following three costly options: compensate the receiver, accept the current allocation, or punish the allocator. Then, a second‐party pseudo interaction is conducted where participants receive more (i.e., advantageous unfair experience) or less (i.e., disadvantageous unfair experience) than others. Finally, participants perform the third‐party justice game again after unfair experiences. Here, we use functional near‐infrared spectroscopy (fNIRS) to measure participants' brain activities during third‐party responses to injustice. We find participants compensate more to the receiver after advantageous unfair experience, which involved enhanced positive emotion, weakened sense of unfairness, and is linked with increased activity in the right dorsolateral prefrontal cortex (rDLPFC). In contrast, participants punish more on the allocator after disadvantageous unfair experience, which might primarily stem from their negative emotional responses, strong sense of unfairness, and is associated with significantly decreased activity in the rDLPFC. Our results suggest that third‐party compensation and punishment involved differential psychological and neural bases. Our findings highlight the crucial roles of second‐party unfair experiences and the corresponding mood responses in third‐party responses to unfairness, and unravel the intermediate neural architecture.

Explaining Individual Differences in Advantageous Inequity Aversion by Social-Affective Trait Dimensions and Family Environment

Humans are averse to both having less (i.e., disadvantageous inequity aversion [IA]) and having more than others (i.e., advantageous IA). However, the social-affective traits that drive individual differences in IA are not well understood. Here, by combining a modified dictator game and a computational model, we found in a sample of incarcerated adolescents ( N = 67) that callous-unemotional traits were specifically associated with low advantageous but not disadvantageous IA. We replicated and extended the finding in a large-scale university student sample ( N = 2,250) by adopting a dimensional approach to social-affective trait measures. We showed that advantageous IA was strongly and negatively associated with a trait dimension characterized by callousness and lack of social emotions (e.g., guilt and compassion). A supportive family environment negatively correlated with this trait dimension and positively with advantageous IA. These results identify a core set of social-affective dimensions specifically associated with advantageous IA.

Intrinsic functional connectivity of medial prefrontal cortex predicts the individual moral bias in economic valuation partially through the moral sensitivity trait

An individual's economic valuation of a given object is biased by the moral status of the persons to whom the object is attached. The neural basis for how such "moral bias" occurs, especially how it is maintained in the resting state, are largely unknown. In the current study, we explored this question by correlating the functional connectivity with participants' behavioral performance measured in a novel task which captured how the economic valuation was influenced by given moral information. Seed-based FC analysis showed that the functional connectivity between the mPFC and the orbital mPFC (omPFC), the mPFC and the precuneus, the mPFC and the left anterior cingulum, were significantly associated with the behavioral index of morality effect on economic valuation. Multivariate machine learning-based regression analysis showed that connections in the mPFC network, as well as in the putamen network could well predict the behavior performance, indicating that this mPFC network and the putamen network were crucial for this moral bias. Our results further revealed that the individuals' personal trait of moral sensitivity served as a mediator between the rsFC of mPFC network and the behavioral index of morality effect on economic valuation.

Social value orientation modulates fairness processing during social decision-making: evidence from behavior and brain potentials

Social value orientation (SVO) characterizes stable individual differences by an inherent sense of fairness in outcome allocations. Using the event-related potential (ERP), this study investigated differences in fairness decision-making behavior and neural bases between individuals with prosocial and proself orientations using the Ultimatum Game (UG). Behavioral results indicated that prosocials were more prone to rejecting unfair offers with stronger negative emotional reactions compared with proselfs. ERP results revealed that prosocials showed a larger P2 when receiving fair offers than unfair ones in a very early processing stage, whereas such effect was absent in proselfs. In later processing stages, although both groups were sensitive to fairness as reflected by an enhanced medial frontal negativity (MFN) for unfair offers and a larger P3 for fair offers, prosocials exhibited a stronger fairness effect on these ERP components relative to proselfs. Furthermore, the fairness effect on the MFN mediated the SVO effect on rejecting unfair offers. Findings regarding emotional experiences, behavioral patterns and ERPs provide compelling evidence that SVO modulates fairness processing in social decision-making, whereas differences in neural responses to unfair vs fair offers as evidenced by the MFN appear to play important roles in the SVO effect on behavioral responses to unfairness.

A Causal Role for the Right Dorsolateral Prefrontal Cortex in Avoidance of Risky Choices and Making Advantageous Selections

In everyday life, risky decision-making relies on multiple cognitive processes including sensitivity to reinforcers, exploration, learning, and forgetting. Neuroimaging evidence suggests that the dorsolateral prefrontal cortex (DLPFC) is involved in exploration and risky decision-making, but the nature of its computations and its causal role remain uncertain. We provide evidence for the role of the DLPFC in value-independent, directed exploration on the Iowa Gambling Task (IGT) and we describe a new computational model to account for the competition of directed exploration and exploitation in guiding decisions. Forty-two healthy human participants were included in a right DLPFC, left DLPFC or sham stimulation groups using continuous theta-burst stimulation (cTBS). Immediately after cTBS, the IGT was completed. Computational modelling was used to account for exploration and exploitation with different combinations with value-based and sensitivity to reinforcers for each group. Applying cTBS to the left and right DLPFC selectively decreased directed exploration on the IGT compared to sham stimulation. Model-based analyses further indicated that the right (but not the left) DLPFC stimulation increased sensitivity to reinforcers, leading to avoidance of risky choices and promoting advantageous choices during the task. Although these findings are based on small sample sizes per group, they nevertheless elucidate the causal role of the right DLPFC in governing the exploration-exploitation tradeoff during decision-making in uncertain and ambiguous contexts.

The neural signatures of egocentric bias in normative decision-making

Bargaining parties often disagree on what fair is, due to the reason that people are prone to believe that what favors oneself is fair, i.e., an egocentric bias. In this study, we investigated the neural signatures underlying egocentric bias in fairness decision-making, conjoining an adapted ultimatum game (UG) with event-related fMRI and functional connectivity. Participants earned monetary rewards with a partner in a production stage, wherein their contributions to the earnings were manipulated. Afterwards, the joint earnings were randomly divided, and the distribution was presented simultaneously with contribution information to participants, who accepted/rejected distributions of earnings as the same manner in standard UG. We identified an egocentric bias in fairness decisions, such that participants frequently rejected self-contributed disadvantageous outcomes, but much less so in response to other-contributed advantageous outcomes, although both involved mismatch between contribution and payoff. This bias was underpinned by regions involved in representing fairness norms, including the anterior insula and dorsal anterior cingulate cortex (dACC). Furthermore, the thalamus activity was predictive of the bias, such that the level of egocentric bias decreased as a function of the activation level of the thalamus. Finally, our functional-connectivity findings indicated that the thalamus worked together with insula and dACC to modulate behavioral egocentric bias in fairness-related decisions. Our findings uncover the neural basis underlying the modulation of egocentric bias in normative decision-making, and highlight the role of neural circuits associated with norm enforcement in this phenomenon.

The neural correlate of mid-value offers in ultimatum game

In the ultimatum game (UG), mid-value offers are unfair but not so unreasonable as to be rejected immediately. As a consequence, they are difficult for responders to evaluate because of the conflict that arises between two key processes, namely inequity aversion and self-interests. Since there is no clear consensus in the literature on event-related potential (ERP) as to how mid-value offers are processed, we designed an experiment to explore how the ability to reject offers influences key ERP signatures. By manipulating the right to reject offers based on game type (ultimatum game, UG or dictator game, DG), our study explored how ERPs were influenced by three types of offers available to participants (fair, unfair and mid-value). We recorded the electroencephalogram results of 28 participants while they responded to the three kinds of offers in the UG and the DG. We observed that mid-value offers in the UG elicited more negative feedback-related negativity and N400 than did the unfair offers. However, these ERP patterns were specific to the UG. Furthermore, we interpreted these results as further electrophysiological evidence of the interaction between the two processing systems during the UG.

Social and Non-social Mechanisms of Inequity Aversion in Non-human Animals

Research over the last decades has shown that humans and other animals reveal behavioral and emotional responses to unequal reward distributions between themselves and other conspecifics. However, cross-species findings about the mechanisms underlying such inequity aversion are heterogeneous, and there is an ongoing discussion if inequity aversion represents a truly social phenomenon or if it is driven by non-social aspects of the task. There is not even general consensus whether inequity aversion exists in non-human animals at all. In this review article, we discuss variables that were found to affect inequity averse behavior in animals and examine mechanistic and evolutionary theories of inequity aversion. We review a range of moderator variables and focus especially on the comparison of social vs. non-social explanations of inequity aversion. Particular emphasis is placed on the importance of considering the experimental design when interpreting behavior in inequity aversion tasks: the tasks used to probe inequity aversion are often based on impunity-game-like designs in which animals are faced with unfair reward distributions, and they can choose to accept the unfair offer, or reject it, leaving them with no reward. We compare inequity-averse behavior in such impunity-game-like designs with behavior in less common choice-based designs in which animals actively choose between fair and unfair rewards distributions. This review concludes with a discussion of the different mechanistic explanations of inequity aversion, especially in light of the particular features of the different task designs, and we give suggestions on experimental requirements to understand the “true nature” of inequity aversion.

How the Brain Converts Negative Evaluation into Performance Facilitation

Surpassing negative evaluation is a recurrent theme of success stories. Yet, there is little evidence supporting the counterintuitive idea that negative evaluation might not only motivate people, but also enhance performance. To address this question, we designed a task that required participants to decide whether taking up a risky challenge after receiving positive or negative evaluations from independent judges. Participants believed that these evaluations were based on their prior performance on a related task. Results showed that negative evaluation caused a facilitation in performance. Concurrent functional magnetic resonance imaging revealed that the motivating effect of negative evaluation was represented in the insula and striatum, while the performance boost was associated with functional positive connectivity between the insula and a set of brain regions involved in goal-directed behavior and the orienting of attention. These findings provide new insight into the neural representation of negative evaluation-induced facilitation.

Love is analogous to money in human brain: Coordinate-based and functional connectivity meta-analyses of social and monetary reward anticipation

Both social and material rewards play a crucial role in daily life and function as strong incentives for various goal-directed behaviors. However, it remains unclear whether the incentive effects of social and material reward are supported by common or distinct neural circuits. Here, we have addressed this issue by quantitatively synthesizing and comparing neural signatures underlying social (21 contrasts, 207 foci, 696 subjects) and monetary (94 contrasts, 1083 foci, 2060 subjects) reward anticipation. We demonstrated that social and monetary reward anticipation engaged a common neural circuit consisting of the ventral tegmental area, ventral striatum, anterior insula, and supplementary motor area, which are intensively connected during both task and resting states. Functional decoding findings indicate that this generic neural pathway mediates positive value, motivational relevance, and action preparation during reward anticipation, which together motivate individuals to prepare well for the response to the upcoming target. Our findings support the common neural currency hypothesis by providing the first meta-analytic evidence to quantitatively show the common involvement of brain regions in both social and material reward anticipation.

How does social information affect charitable giving?: Empathic concern promotes support for underdog recipient

Charitable giving represents a unique cooperative characteristic of humans. In today's environment with social media, our charitable decisions seem to be influenced by social information such as a project's popularity. Here we report three experiments that examined people's reactions to social information about a charitable endeavor and their psychophysiological underpinnings. Participants were first solicited to make donations to either the Africa or Syria project of UNICEF. Then participants were provided an opportunity to learn social information (i.e., how much each project had raised from previous participants) and change their decision if desired. Contrary to expectation, participants who learned that their initial preferences were consistent with the majority of previous participants' choices exhibited a sizable tendency to switch to the less popular project in their final choices. This anti-conformity pattern was robust across the three experiments. Eye-tracking data (gaze bias and pupil dilation) indicated that these "Changers" were more physiologically aroused and formed more differential valuations between the two charity projects, compared to "Keepers" who retained their initial preferences after viewing the social information. These results suggest that social information about relative popularity may evoke empathic concern for the worse-off target, in line with the human tendency to avoid unequal distributions.

Spreading inequality: neural computations underlying paying-it-forward reciprocity

People tend to pay the generosity they receive from a person forward to someone else even if they have no chance to reciprocate directly. This phenomenon, known as paying-it-forward (PIF) reciprocity, crucially contributes to the maintenance of a cooperative human society by passing kindness among strangers and has been widely studied in evolutionary biology. To further examine its neural implementation and underlying computations, we used functional magnetic resonance imaging together with computational modeling. In a modified PIF paradigm, participants first received a monetary split (i.e. greedy, equal or generous) from either a human partner or a computer. They then chose between two options involving additional amounts of money to be allocated between themselves and an uninvolved person. Behaviorally, people forward the previously received greed/generosity towards a third person. The social impact of previous treatments is integrated into computational signals in the ventromedial prefrontal cortex and the right temporoparietal junction during subsequent decision making. Our findings provide insights to understand the proximal origin of PIF reciprocity.

Interactive effects of OXTR and GAD1 on envy-associated behaviors and neural responses

Inequity aversion (negative feelings induced by outcome differences between the self and other) plays a key role in human social behaviors. The neurotransmitters oxytocin and GABA have been implicated in neural responses to inequity. However, it remains poorly understood not only how individual genetic factors related to oxytocin and GABA affect the neural mechanisms behind inequity aversion, but also how these genes interact. To address these issues, we examined relationships between genotypes, behavioral decisions and brain activities during the ultimatum game. We identified interactive effects between the polymorphisms of the oxytocin receptor gene (OXTR) and glutamate decarboxylase 1 gene for GABA synthesis (GAD1) on envy aversion (i.e., disadvantageous inequity aversion) and on envy-induced activity in the dorsal ACC (dACC). Thus, our integrated approach suggested interactive genetic effects between OXTR and GAD1 on envy aversion and the underlying neural substrates.

Inequality signals in dorsolateral prefrontal cortex inform social preference models

Humans typically display inequality aversion in social situations, which manifests itself as a preference for fairer distributions of resources. However, people differ in the degree to which they dislike being worse off [disadvantageous inequality (DI) aversion] or better off [advantageous inequality (AI) aversion] than others. Competing models explain such behavior by focusing on aversion to payoff differences, maximization of total payoff or reciprocity. Using functional near-infrared spectroscopy, we asked which of these theories could better explain dorsolateral prefrontal cortex (dlPFC) activity while participants accepted or punished fair vs unfair monetary transfers in an anonymous norm compliance task. We found that while all participants exhibited DI aversion, there were substantial differences in preferences for AI, which were strongly predicted by dlPFC activation. Model comparisons revealed that both punishment behavior and prefrontal activity were best explained by a model that allowed for AI seeking rather than imposing aversion. Moreover, enhancing this model by taking into account behavioral response times, as a proxy for choice difficulty, further improved model fits. Our data provide evidence that the dlPFC encodes subjective values of payoff inequality and that this representation is richer than envisaged by standard models of social preferences.

The role of Prefrontal Cortex in a Battle of the Sexes Dilemma involving a Conflict between Tribal and Romantic love

The neural basis of dilemmas involving decisions with profound affective impact, such as in romantic life, remains to be understood. The "Battle of the Sexes" is a paradigm from Game Theory that can be used to experimentally address such dilemmas. A form of in-group love, tribal love in football fans, provides the opportunity to study strong affective dilemmas when tribal and romantic love compete for hedonic decision-making. Here, we used for the first time a "Battle of the Sexes" dilemma using fMRI. We investigated, in 44 male football fans, the neural correlates of cooperative behaviour under conflicting choices in the context of romantic versus tribal love. We identified a critical functional segregation of prefrontal regions in affective decision-making. The orbitofrontal cortex signalled emotional appraisal of the dilemma. The medial anterolateral and the ventromedial prefrontal cortices reflected reciprocal cooperation instead of selfish engagement in football-related activities. The lateral portion of anterolateral prefrontal cortex was recruited during ultimate deliberation. In sum, emotional appraisal and rational choice reflected a contiguous functional parcellation in anterolateral prefrontal cortex: appraisal (medial) vs. choice (lateral region).

Distinguishing neural correlates of context-dependent advantageous- and disadvantageous-inequity aversion

Humans can integrate social contextual information into decision-making processes to adjust their responses toward inequity. This context dependency emerges when individuals receive more (i.e., advantageous inequity) or less (i.e., disadvantageous inequity) than others. However, it is not clear whether context-dependent processing of advantageous and disadvantageous inequity involves differential neurocognitive mechanisms. Here, we used fMRI to address this question by combining an interactive game that modulates social contexts (e.g., interpersonal guilt) with computational models that enable us to characterize individual weights on inequity aversion. In each round, the participant played a dot estimation task with an anonymous coplayer. The coplayer would receive pain stimulation with 50% probability when either of them responded incorrectly. At the end of each round, the participant completed a variant of dictator game, which determined payoffs for him/herself and the coplayer. Computational modeling demonstrated the context dependency of inequity aversion: when causing pain to the coplayer (i.e., guilt context), participants cared more about the advantageous inequity and became more tolerant of the disadvantageous inequity, compared with other conditions. Consistently, neuroimaging results suggested the two types of inequity were associated with differential neurocognitive substrates. While the context-dependent processing of advantageous inequity was associated with social- and mentalizing-related processes, involving left anterior insula, right dorsolateral prefrontal cortex, and dorsomedial prefrontal cortex, the context-dependent processing of disadvantageous inequity was primarily associated with emotion- and conflict-related processes, involving left posterior insula, right amygdala, and dorsal anterior cingulate cortex. These results extend our understanding of decision-making processes related to inequity aversion.

The Neural Basis of Social Influence in a Dictator Decision

Humans tend to reduce inequitable distributions. Previous neuroimaging studies have shown that inequitable decisions are related to brain regions that associated with negative emotion and signaling conflict. In the highly complex human social environment, our opinions and behaviors can be affected by social information. In current study, we used a modified dictator game to investigate the effect of social influence on making an equitable decision. We found that the choices of participants in present task was influenced by the choices of peers. However, participants' decisions were influenced by equitable rather than inequitable group choices. fMRI results showed that brain regions that related to norm violation and social conflict were related to the inequitable social influence. The neural responses in the dorsomedial prefrontal cortex, rostral cingulate zone, and insula predicted subsequent conforming behavior in individuals. Additionally, psychophysiological interaction analysis revealed that the interconnectivity between the dorsal striatum and insula was elevated in advantageous inequity influence versus no-social influence conditions. We found decreased functional connectivity between the medial prefrontal cortex and insula, supplementary motor area, posterior cingulate gyrus and dorsal anterior cingulate cortex in the disadvantageous inequity influence versus no-social influence conditions. This suggests that a disadvantageous inequity influence may decrease the functional connectivity among brain regions that are related to reward processes. Thus, the neural mechanisms underlying social influence in an equitable decision may be similar to those implicated in social norms and reward processing.

The good lies: Altruistic goals modulate processing of deception in the anterior insula

When it comes to lies, the beneficiaries of one's dishonesty play an important role in the decision-making process. Altruistic lies that are made with the intention of benefiting others are a specific type of lies and very common in real life. While it has been shown that altruistic goals influence (dis)honest behaviors, the neural substrates of this effect is still unknown. To reveal how the brain integrates altruistic goals into (dis)honest decisions, this study used functional magnetic resonance imaging to examine the neural activity of participants in a real incentivized context while they were making (dis)honest decisions. We manipulated the beneficiaries of individuals' decisions (self vs. a charity) and whether the choices of higher payoffs involved deception or not. While finding that participants lied more often to benefit charities than for themselves, we observed that the altruistic goal of benefiting a charity, compared with the self-serving goal, reduced the activity in the anterior insula (AI) when lying to achieve higher payoffs. Furthermore, the degree of altruistic goal-induced reduction of AI activity was positively correlated with the degree of altruistic goal-induced reduction of honesty concerns. These results suggest that the AI serves as a neural hub in modulating the effect of altruistic goals on deception, which shed light on the underlying neural mechanism of altruistic lies. Hum Brain Mapp 38:3675-3690, 2017. © 2017 Wiley Periodicals, Inc.

Ingroup/outgroup membership modulates fairness consideration: neural signatures from ERPs and EEG oscillations

Previous studies have shown that ingroup/outgroup membership influences individual’s fairness considerations. However, it is not clear yet how group membership influences brain activity when a recipient evaluates the fairness of asset distribution. In this study, subjects participated as recipients in an Ultimatum Game with alleged members of both an experimentally induced ingroup and outgroup. They either received extremely unequal, moderately unequal, or equal offers from proposers while electroencephalogram was recorded. Behavioral results showed that the acceptance rates for unequal offers were higher when interacting with ingroup partners than with outgroup partners. Analyses of event related potentials revealed that proposers’ group membership modulated offer evaluation at earlier processing stages. Feedback-related negativity was more negative for extremely and moderately unequal offers compared to equal offers in the ingroup interaction whereas it did not show differential responses to different offers in the outgroup interaction. Analyses of event related oscillations revealed that the theta power (4–6 Hz) was larger for moderately unequal offers than equal offers in the ingroup interaction whereas it did not show differential responses to different offers in the outgroup interaction. Thus, early mechanisms of fairness evaluation are strongly modulated by the ingroup/outgroup membership of the interaction partner.

Neural signatures of social conformity: A coordinate-based activation likelihood estimation meta-analysis of functional brain imaging studies

People often align their behaviors with group opinions, known as social conformity. Many neuroscience studies have explored the neuropsychological mechanisms underlying social conformity. Here we employed a coordinate-based meta-analysis on neuroimaging studies of social conformity with the purpose to reveal the convergence of the underlying neural architecture. We identified a convergence of reported activation foci in regions associated with normative decision-making, including ventral striatum (VS), dorsal posterior medial frontal cortex (dorsal pMFC), and anterior insula (AI). Specifically, consistent deactivation of VS and activation of dorsal pMFC and AI are identified when people's responses deviate from group opinions. In addition, the deviation-related responses in dorsal pMFC predict people's conforming behavioral adjustments. These are consistent with current models that disagreement with others might evoke "error" signals, cognitive imbalance, and/or aversive feelings, which are plausibly detected in these brain regions as control signals to facilitate subsequent conforming behaviors. Finally, group opinions result in altered neural correlates of valuation, manifested as stronger responses of VS to stimuli endorsed than disliked by others.

Tend to Compare and Tend to Be Fair: The Relationship between Social Comparison Sensitivity and Justice Sensitivity

Social comparison is a prerequisite for processing fairness, although the two types of cognition may be associated with different emotions. Whereas social comparison may induce envy, the perception of unfairness may elicit anger. Yet, it remains unclear whether people who tend to have a strong sense of fairness also tend to compare themselves more with others. Here, Study 1 used a modified ultimatum game (UG) and a social comparison game (SCG) to examine the relationship between justice sensitivity and social comparison sensitivity in 51 young adults. Study 2 examined self-reported social comparison and justice sensitivity in 142 young adults. Both studies showed a positive correlation between social comparison sensitivity and justice sensitivity. We reason that social comparison and justice sensitivity have an important positive correlation in human decision-making. The rejection of self-disadvantageous inequality offers may be due to the social comparison effect, which suggests that the tendency to compare oneself with others may contribute to having a strong sense of justice. Our findings suggest that the predictions of game theory may vary depending on the social culture context and incorporating notions of fairness and social comparison tendency may be essential to better predict the actual behavior of players in social interactive situations.

Diffusion of responsibility attenuates altruistic punishment: A functional magnetic resonance imaging effective connectivity study

Humans altruistically punish violators of social norms to enforce cooperation and pro-social behaviors. However, such altruistic behaviors diminish when others are present, due to a diffusion of responsibility. We investigated the neural signatures underlying the modulations of diffusion of responsibility on altruistic punishment, conjoining a third-party punishment task with event-related functional magnetic resonance imaging and multivariate Granger causality mapping. In our study, participants acted as impartial third-party decision-makers and decided how to punish norm violations under two different social contexts: alone (i.e., full responsibility) or in the presence of putative other third-party decision makers (i.e., diffused responsibility). Our behavioral results demonstrated that the diffusion of responsibility served as a mediator of context-dependent punishment. In the presence of putative others, participants who felt less responsible also punished less severely in response to norm violations. Our neural results revealed that underlying this behavioral effect was a network of interconnected brain regions. For unfair relative to fair splits, the presence of others led to attenuated responses in brain regions implicated in signaling norm violations (e.g., AI) and to increased responses in brain regions implicated in calculating values of norm violations (e.g., vmPFC, precuneus) and mentalizing about others (dmPFC). The dmPFC acted as the driver of the punishment network, modulating target regions, such as AI, vmPFC, and precuneus, to adjust altruistic punishment behavior. Our results uncovered the neural basis of the influence of diffusion of responsibility on altruistic punishment and highlighted the role of the mentalizing network in this important phenomenon. Hum Brain Mapp 37:663-677, 2016. © 2015 Wiley Periodicals, Inc.

Social status modulates the neural response to unfairness

In human society, which is organized by social hierarchies, resources are usually allocated unequally and based on social status. In this study, we analyze how being endowed with different social statuses in a math competition affects the perception of fairness during asset allocation in a subsequent Ultimatum Game (UG). Behavioral data showed that when participants were in high status, they were more likely to reject unfair UG offers than in low status. This effect of social status correlated with activity in the right anterior insula (rAI) and with the functional connectivity between the rAI and a region in the anterior middle cingulate cortex, indicating that these two brain regions are crucial for integrating contextual factors and social norms during fairness perception. Additionally, there was an interaction between social status and UG offer fairness in the amygdala and thalamus, implicating the role of these regions in the modulation of social status on fairness perception. These results demonstrate the effect of social status on fairness perception and the potential neural underpinnings for this effect.

Follow the heart or the head? The interactive influence model of emotion and cognition

The experience of emotion has a powerful influence on daily-life decision making. Following Plato's description of emotion and reason as two horses pulling us in opposite directions, modern dual-system models of decision making endorse the antagonism between reason and emotion. Decision making is perceived as the competition between an emotion system that is automatic but prone to error and a reason system that is slow but rational. The reason system (in "the head") reins in our impulses (from "the heart") and overrides our snap judgments. However, from Darwin's evolutionary perspective, emotion is adaptive, guiding us to make sound decisions in uncertainty. Here, drawing findings from behavioral economics and neuroeconomics, we provide a new model, labeled "The interactive influence model of emotion and cognition," to elaborate the relationship of emotion and reason in decision making. Specifically, in our model, we identify factors that determine when emotions override reason and delineate the type of contexts in which emotions help or hurt decision making. We then illustrate how cognition modulates emotion and how they cooperate to affect decision making.

Neural signatures of fairness-related normative decision making in the ultimatum game: a coordinate-based meta-analysis

The willingness to incur personal costs to enforce prosocial norms represents a hallmark of human civilization. Although recent neuroscience studies have used the ultimatum game to understand the neuropsychological mechanisms that underlie the enforcement of fairness norms; however, a precise characterization of the neural systems underlying fairness-related norm enforcement remains elusive. In this study, we used a coordinate-based meta-analysis on functional magnetic resonance imaging (fMRI) studies using the ultimatum game with the goal to provide an additional level of evidence for the refinement of the underlying neural architecture of this human puzzling behavior. Our results demonstrated a convergence of reported activation foci in brain networks associated with psychological components of fairness-related normative decision making, presumably reflecting a reflexive and intuitive system (System 1) and a reflective and deliberate system (System 2). System 1 (anterior insula, ventromedial prefrontal cortex [PFC]) may be associated with the reflexive and intuitive responses to norm violations, representing a motivation to punish norm violators. Those intuitive responses conflict with economic self-interest, encoded in the dorsal anterior cingulate cortex (ACC), which may engage cognitive control from a reflective and deliberate System 2 to resolve the conflict by either suppressing (ventrolateral PFC, dorsomedial PFC, left dorsolateral PFC, and rostral ACC) the intuitive responses or over-riding self-interest (right dorsolateral PFC). Taken together, we suggest that fairness-related norm enforcement recruits an intuitive system for rapid evaluation of norm violations and a deliberate system for integrating both social norms and self-interest to regulate the intuitive system in favor of more flexible decision making.

Neural correlates of advantageous and disadvantageous inequity in sharing decisions

Humans have a strong preference for fair distributions of resources. Neuroimaging studies have shown that being treated unfairly coincides with activation in brain regions involved in signaling conflict and negative affect. Less is known about neural responses involved in violating a fairness norm ourselves. Here, we investigated the neural patterns associated with inequity, where participants were asked to choose between an equal split of money and an unequal split that could either maximize their own (advantageous inequity) or another person’s (disadvantageous inequity) earnings. Choosing to divide money unequally, irrespective who benefited from the unequal distribution, was associated with activity in the dorsal anterior cingulate cortex, anterior insula and the dorsolateral prefrontal cortex. Inequity choices that maximized another person’s profits were further associated with activity in the ventral striatum and ventromedial prefrontal cortex. Taken together, our findings show evidence of a common neural pattern associated with both advantageous and disadvantageous inequity in sharing decisions and additional recruitment of neural circuitry previously linked to the computation of subjective value and reward when violating a fairness norm at the benefit of someone else.

The neural signature of escalating frustration in humans

Mammalian studies show that frustration is experienced when goal-directed activity is blocked. Despite frustration's strongly negative role in health, aggression and social relationships, the neural mechanisms are not well understood. To address this we developed a task in which participants were blocked from obtaining a reward, an established method of producing frustration. Levels of experienced frustration were parametrically varied by manipulating the participants' motivation to obtain the reward prior to blocking. This was achieved by varying the participants' proximity to a reward and the amount of effort expended in attempting to acquire it. In experiment 1, we confirmed that proximity and expended effort independently enhanced participants' self-reported desire to obtain the reward, and their self-reported frustration and response vigor (key-press force) following blocking. In experiment 2, we used functional magnetic resonance imaging (fMRI) to show that both proximity and expended effort modulated brain responses to blocked reward in regions implicated in animal models of reactive aggression, including the amygdala, midbrain periaqueductal grey (PAG), insula and prefrontal cortex. Our findings suggest that frustration may serve an energizing function, translating unfulfilled motivation into aggressive-like surges via a cortical, amygdala and PAG network.