Social value orientation modulates the FRN and P300 in the chicken game

An EEG Dataset of Neural Signatures in a Competitive Two-Player Game Encouraging Deceptive Behavior

Studying deception is vital for understanding decision-making and social dynamics. Recent EEG research has deepened insights into the brain mechanisms behind deception. Standard methods in this field often rely on memory, are vulnerable to countermeasures, yield false positives, and lack real-world relevance. Here, we present a comprehensive dataset from an EEG-monitored competitive, two-player card game designed to elicit authentic deception behavior. Our extensive dataset contains EEG data from 12 pairs (N = 24 participants with role switching), controlled for age, gender, and risk-taking, with detailed labels and annotations. The dataset combines standard event-related potential and microstate analyses with state-of-the-art decoding approaches of four scenarios: spontaneous/instructed truth-telling and lying. This demonstrates game-based methods' efficacy in studying deception and sets a benchmark for future research. Overall, our dataset represents a unique resource with applications in cognitive neuroscience and related fields for studying deception, competitive behavior, decision-making, inter-brain synchrony, and benchmarking of decoding frameworks in a difficult, high-level cognitive task.

Processing abnormalities in monetary outcome evaluations among male individuals with opioid use disorder: evidence from feedback-related negativity

Background: Numerous studies have highlighted the pivotal role of alterations in the monetary reward system in the development and maintenance of substance use disorder (SUD). Although these alterations have been well documented in various forms of SUD, the electrophysiological mechanisms specific to opioid use disorder (OUD) remain underexplored. Understanding these mechanisms is critical for developing targeted interventions and advancing theories of addiction specific to opioid use.Objectives: To explore abnormalities in monetary reward outcome processing in males with OUD. We hypothesized that control individuals would show higher feedback-related negativity (FRN) to losses, unlike those in the OUD group, where FRN to losses and gains would not differ significantly.Methods: Fifty-seven participants (29 male individuals with OUD [heroin] and 28 male controls) were evaluated. A combination of the monetary incentive delay task (MIDT) and event-related potential (ERP) technology was used to investigate electrophysiological differences in monetary reward feedback processing between the OUD and healthy control groups.Results: We observed a significant interaction between group (control vs. OUD) and monetary outcome (loss vs. gain), indicated by p < .05 and η2p = 0.116. Specifically, control participants showed stronger negative FRN to losses than gains (p < .05), unlike the OUD group (p > .05).Conclusion: This study's FRN data indicate that males with OUD show altered processing of monetary rewards, marked by reduced sensitivity to loss. These findings offer electrophysiological insights into why males with OUD may pursue drugs despite potential economic downsides.

Comparison with others influences encoding and recognition of their faces: Behavioural and ERP evidence

In daily life, faces are often memorized within contexts involving interpersonal interactions. However, little is known about whether interpersonal interaction-related contexts influence face memory. The present study aimed to understand this question by investigating how social comparison-related context affects face encoding and recognition. To address this issue, 40 participants were informed that they and another player each played a monetary game and were then presented with both of their outcomes (either monetary gain or loss). Subsequently, participants were shown the face of the player whom they were just paired with. After all the faces had been encoded, participants were asked to perform a sudden old/new recognition task involving these faces. The results showed that, during the encoding phase, another player's monetary gain, compared to loss, resulted in more negative responses in the N170 and early posterior negativity (EPN)/N250 to relevant players' faces when participants encountered monetary loss and a smaller late positive potential (LPP) response irrespective of self-related outcomes. In the subsequent recognition phase, preceding another player's monetary gain as compared to loss led to better recognition performance and stronger EPN/N250 and LPP responses to the faces of relevant players when participants had lost some amount of money. These findings suggest that the social comparison-related context, particularly self-disadvantageous outcomes in the context, influences the memory of comparators' faces.

The influence of self-esteem on interpersonal and competence evaluations: electrophysiological evidence from an ERP study

Using event-related potentials, this study examined how self-esteem affects neural responses to competence (interpersonal) feedback when the need for relatedness (competence) is thwarted or met. Participants with low and high self-esteem acted as advisors who selected one of two options for a putative advisee. Subsequently, they passively observed the advisee, accepted, or rejected their advice (i.e. interpersonal feedback) and received correct or incorrect outcomes (i.e. competence feedback). When interpersonal feedback was followed by competence feedback, high self-esteem participants showed a smaller P3 following incorrect than correct outcomes, irrespective of whether the advice had been accepted or rejected. However, low self-esteem participants showed this P3 effect only when the advice was rejected, and the P3 difference disappeared when the advice was accepted. When competence feedback was followed by interpersonal feedback, both low self-esteem and high self-esteem individuals showed a larger P2 for rejection than for acceptance and a larger late potential component for incorrect than correct outcomes. These findings suggest that when interpersonal feedback is followed by competence feedback, low self-esteem and high self-esteem individuals have a desire for self-positivity. When competence feedback is followed by interpersonal feedback, they may have motives for self-change. Our findings shed light on the motivational mechanisms for self-esteem and feedback.

Self-construal modulates context-based social comparison preferences in outcome evaluations

Self-construal (SC) describes how people perceive the relationship between themselves and others and is usually divided into interdependent and independent types. Several studies have been conducted on how people with independent and interdependent SC process their own and others' outcomes. However, few studies have investigated the influence of SC on outcome evaluation in a social comparison context. To explore this, we randomly assigned participants to interdependent and independent SC priming groups and analyzed the affects and electrophysiological responses generated when they played gambling games with two pseudo-players. The results showed that self-gambling state, SC, and social comparison interacted to influence feedback-related negativity (FRN). In the self-win condition, performances that differed from others elicited more negative FRN than evenness for both the interdependent and independent groups. In the self-loss condition, this effect was only found in the independent group. These results suggest that the outcome evaluation patterns in social contexts are not fixed but vary according to self-gambling state and SC.

The Effect of Social Value Orientation on Theta to Alpha Ratio in Resource Allocation Games

The social value orientation (SVO) has a profound effect on the strategic decision making in economic choices and the ability to succeed in coordination games. With that in mind, in this study we wanted to examine an electrophysiological measure elicited in different resource allocation problems that affect the preferences of the player. We recorded EEG from participants while they were engaged in different allocation problems varying in the magnitude of reward and the difference size between alternative choices. We found that the theta to alpha ratio (TAR) can differentiate between individualistic and prosocial players. Specifically, individualistic players were more sensitive to the magnitude of the overall payoff (reflected by the radius size) as well as to the difference between two reward alternatives in the resource allocation task. These two variables, reward magnitude, and the difference between payoff alternatives, have significantly differentiated between the TAR levels of prosocials and proselfs (p < 0.001). For extreme differences (small or large), TAR was higher in comparison to medium sized differences. Our results demonstrated that in resource allocation games the TAR can be predicted based on the parameters of the task and the SVO category of the player (prosocial or individualistic). Specifically, an interaction was found between the attractiveness of the reward (radius) as well as the conflict between alternatives (Δ∅) and the SVO of the player at a significance level of p < 0.0001. These results highlight the importance of the SVO construct in economic decision choices varying in both reward magnitude and the proximity between alternative choices. Suggestions for future studies are discussed.

Social distance modulates the influence of social observation on pro-environmental behavior: An event-related potential (ERP) study

Pro-environmental behavior benefits the environment but is individually costly. Therefore, understanding the neural processes of pro-environmental behavior can advance our knowledge of its implicit cost-benefit calculations and mechanisms. Previous studies have focused separately on the effects of social distance and social observation on explicit pro-environmental behavior responses, yet the underlying neurophysiological mechanism remains unknown. Using the event-related potentials (ERPs), we investigated the neural responses to the effects of social distance and social observation on pro-environmental behavior. Participants were instructed to decide between self-interest and pro-environmental choices towards different social distance targets (family members, acquaintances, or strangers) under observable and non-observable conditions. The behavioral results demonstrated that the rate of pro-environmental choices towards acquaintances and strangers was higher under the observable condition than under the non-observable condition. Nonetheless, the rate of pro-environmental choices was higher-unaffected by social observation-towards family members than towards acquaintances and strangers. The ERP results showed that the P2 and P3 amplitudes were smaller under the observable than under the non-observable condition when the potential bearers of environmental decisions were acquaintances and strangers. However, this difference did not emerge when the potential bearers of environmental decisions were family members. The ERP findings of smaller P2 and P3 amplitudes suggest that social observation may reduce the deliberate calculation of personal costs, thereby promoting individuals' pro-environmental behaviors towards acquaintances and strangers.

Influence of advisees' facial feedback on subsequent advice-giving by advisors: Evidence from the behavioral and neurophysiological approach

Previous work has demonstrated the interpersonal implications of advisees' decisions (acceptance or rejection) on advisors' advice-giving behavior in subsequent exchanges. Here, using an ERP technique, we investigated how advisees' facial feedback (smiling, neutral, or frowning) accompanying their decisions (acceptance or rejection) influenced advisors' feedback evaluation from advisees and their advice-giving in subsequent exchanges. Behaviorally, regardless of whether the advice was accepted or rejected, advisors who received smiling-expression feedback would show higher willingness rates in subsequent advice-giving decisions, while advisors who received frowning-expression feedback would show lower willingness rates. On the neural level, in the feedback evaluation stage, the FRN and P3 responses were not sensitive to facial feedback. In contrast, frowning-expression feedback elicited a larger LPC amplitude than neutral- and smiling-expression feedback, regardless of whether the advice was accepted or rejected. In the advice decision stage, advisors who received neutral-expression feedback showed a larger N2 in making decisions than advisors who received frowning-expression feedback only after the advice was rejected. Additionally, Advisors who received smiling- and neutral-expression feedback showed a larger P3 in making decisions than advisors who received frowning-expression feedback only after the advice was accepted. In sum, the current findings extended previous research findings by showing that the effect of advisees' facial expressions on the advisors' advice-giving existed in multiple stages, including both the feedback evaluation stage and the advice decision stage.

Risk decision: The self-charity discrepancies in electrophysiological responses to outcome evaluation

Previous studies have examined the outcome evaluation related to the self and other, and recent research has explored the outcome evaluation of the self and other with pro-social implications. However, the evaluation processing of outcomes in the group in need remains unclear. This study has examined the neural mechanisms of evaluative processing by gambling for the self and charity, respectively. At the behavioral level, when participants make decisions for themselves, they made riskier decisions following the gain than loss in small outcomes and engage in more risky behaviors following the loss than gain in large outcomes. However, magnitude and valence did not affect the next risky behavior when participants made decisions for the charity. At the neurophysiological level, the results found that the FRN was larger for the charity outcome than for the self-outcome. For FRN, the valence difference of small outcomes was smaller than that of large outcomes. The P3 response was larger for the self-outcome than for the charity outcome. Meanwhile, compared with the small outcome, the self-charity discrepancies have a significant difference in large outcomes. In addition, the FRN amplitude for self in large outcomes was negatively correlated with the upcoming risky choices, regardless of outcome valence. The behavioral results suggest that people are more likely to optimize strategies for themselves than for the charity. The ERP findings indicated that people focus more on charity outcome than self-outcome in the early stage. In the middle and late stages, people turn attention to their outcomes, and the difference between self’s and charity’s outcome varies with the magnitude. Specifically, it is only in large outcomes that people engage more emotional attention or motivation in their outcomes, but self and charity outcomes had a similar emotional engagement in small outcomes.

The different role of trait empathy and state social exclusion empathy on subsequent feelings about gambling outcome：Evidence from event-related potentials and time-frequency decompositions

Empathy plays an essential role in determining how we understand and respond to others' emotional experiences. Previous studies have mainly focused on the influencing factors of physical pain and monetary loss empathy, as well as on their effects on subsequent feelings. However, little is known about social pain empathy and its influence on subsequent feelings, and the role of personal trait empathy. In this study, we performed Cyberball Games and gambling tasks to explore the effect of social exclusion empathy on subsequent feelings for gambling outcomes (others' losses and gains) by analyzing the brain activity of excluded and non-excluded players at the gambling outcome feedback stage. It was found that both feedback-related negativity (FRN) and theta-band oscillatory are more negative for loss outcome than gain for the excluded players, while these effects cannot be found for the non-excluded players. Furthermore, we only observed a larger P300 amplitude in the gain outcome than that of loss, regardless of the players' role. More interestingly, we found state social pain empathy is negatively correlated with the d-FRN amplitude under non-excluded conditions, while trait empathy is positively correlated with P300 amplitude regardless of the players' role. These results provide insight into the different roles of state social pain empathy and trait empathy on subsequent gambling outcomes. Furthermore, different from previous studies, the current results show that d-FRN could reflect the state empathy discrepancy rather than the biomarker of state empathy.

Prosociality moderates outcome evaluation in competition tasks

The current study investigated the effect of prosociality on outcome evaluation without involving social comparison and reward processing in face-to-face competition tasks. The results showed that when faced with medium and large outcome feedback, the feedback-related negativity (FRN) amplitude induced in high-prosocial individuals was significantly more negative than that of low-prosocial individuals. In addition, the P300 amplitude induced in high-prosocial individuals was smaller than that in low-prosocial individuals in the face of large outcome feedback; hence, the prosociality score was significantly correlated with FRN amplitude. However, there was no significant difference in FRN between high-and low-prosocial individuals in the face of small outcome feedback. It was concluded that individual prosocial traits can moderate outcome evaluation.

Cooperate or aggress? An opponent's tendency to cooperate modulates the neural dynamics of interpersonal cooperation

Humans are social animals and need to cooperate to survive. However, individuals are not cooperative in every social interaction, and their cooperation may depend on social context. The present study used a social dilemma game to investigate whether an opponent's tendency to be cooperative over time influenced a player's behavior and neural response to outcomes in the game. University students ("players") thought they were playing against other students ("opponents") in the Chicken Game but were actually playing against a programmed computer. Participants were randomly assigned to play with an opponent who tended to be competitive (cooperative 20% of the time) or who tended to be cooperative (cooperative 80% of the time). The results showed that early in the game, participants in both groups adopted a "tit-for-tat" strategy. However, as the game progressed and the opponent's behavioral tendency became more noticeable, players in the competitive-opponent group became generally more cooperative to limit their losses. ERPs analyses indicated that players had a higher P300 and larger theta power in response to the opponent's aggression but not to the opponent's cooperation when their opponent showed a tendency to be cooperative vs. competitive. The results suggest that people adjust their cooperative behavior based on their opponent's behavior in social interaction, and aggression captures more attention than cooperation in this process.

Neuro-Behavioral Dynamic Prediction of Interpersonal Cooperation and Aggression

How to quickly predict an individual's behavioral choices is an important issue in the field of human behavior research. Using noninvasive electroencephalography, we aimed to identify neural markers in the prior outcome-evaluation stage and the current option-assessment stage of the chicken game that predict an individual's behavioral choices in the subsequent decision-output stage. Hierarchical linear modeling-based brain-behavior association analyses revealed that midfrontal theta oscillation in the prior outcome-evaluation stage positively predicted subsequent aggressive choices; also, beta oscillation in the current option-assessment stage positively predicted subsequent cooperative choices. These findings provide electrophysiological evidence for the three-stage theory of decision-making and strengthen the feasibility of predicting an individual's behavioral choices using neural oscillations.

Mutual gaze with a robot affects human neural activity and delays decision-making processes

In most everyday life situations, the brain needs to engage not only in making decisions but also in anticipating and predicting the behavior of others. In such contexts, gaze can be highly informative about others’ intentions, goals, and upcoming decisions. Here, we investigated whether a humanoid robot’s gaze (mutual or averted) influences the way people strategically reason in a social decision-making context. Specifically, participants played a strategic game with the robot iCub while we measured their behavior and neural activity by means of electroencephalography (EEG). Participants were slower to respond when iCub established mutual gaze before their decision, relative to averted gaze. This was associated with a higher decision threshold in the drift diffusion model and accompanied by more synchronized EEG alpha activity. In addition, we found that participants reasoned about the robot’s actions in both conditions. However, those who mostly experienced the averted gaze were more likely to adopt a self-oriented strategy, and their neural activity showed higher sensitivity to outcomes. Together, these findings suggest that robot gaze acts as a strong social signal for humans, modulating response times, decision threshold, neural synchronization, as well as choice strategies and sensitivity to outcomes. This has strong implications for all contexts involving human-robot interaction, from robotics to clinical applications.

Working memory load reduces the processing of outcome evaluation involving others but not oneself: Event-related potential evidence

Previous event-related potential (ERP) studies have suggested that self-related and non-self-related outcomes are processed simultaneously. However, the studies investigated situations in which individuals had sufficient attentional/cognitive resources to process both of the outcomes. It is unknown whether self-related and non-self-unrelated outcomes could still be processed simultaneously when resources are limited. To address this issue, 32 female participants in the present study were asked to perform a working memory task. To manipulate the amount of available attentional/cognitive resources, participants were asked to memorize a letter in the low load condition and five letters in the high load condition. During letter consolidation, participants were informed that they and another player each performed a gambling task and were subsequently presented with both of the outcomes. ERP results showed that others' monetary loss elicited larger P200 and late positive potential amplitudes than others' monetary gain under a low working memory load, whereas a high load reduced these effects. However, working memory load did not influence the effect of self-outcome on ERP responses. Therefore, the findings suggest that the amount of available attentional/cognitive resources alters the evaluation of non-self-related but not self-related outcomes.

Context-based interpersonal relationship modulates social comparison between outcomes: an event-related potential study

Social comparison is a common behavior that largely determines people's experience of decision outcome. Previous research has showed that interpersonal relationship plays a pivotal role in social comparison. In the current study, we investigated whether the manipulation of context-based relationship would affect participants' comparison of self-outcome and other-outcome. Participants first finished a trust game with likeable (dislikeable) partner and then they were involved in a gambling task and observed the outcomes for themselves and for partners. According to self-reports, participants were more satisfied with likeable partner's gains than losses only when they received gains, but they were always more satisfied with dislikeable player's losses compared to gains. Event-related potentials including the feedback-related negativity (FRN), P3 and late positive component (LPC) were sensitive to context-based relationship. Specifically, the prediction error signal (indexed by the FRN) was largest when participants received losses but dislikeable player received gains. Meanwhile, the P3 indicates that participants had stronger motivation to outperform dislikeable player. Finally, the LPC was larger when participants received the same outcomes with dislikeable players. In general, our results support the key point of the self-evaluation maintenance model that personal closeness modulates subjective sensitivity when drawing a comparison of one's outcomes with other's outcomes.

Neuroscience and climate change: How brain recordings can help us understand human responses to climate change

There is little published neuroscience research on the psychology of climate change. This review outlines how carefully designed experiments that measure key neural processes, linked to specific cognitive processes, can provide powerful tools to answer research questions in climate change psychology. We review relevant literature from social neuroscience that can be applicable to environmental research-the neural correlates of fairness and cooperation, altruistic behaviour and personal values-and discuss important factors when translating environmental psychology constructs to neuroscientific measurement. We provide a practical overview of how to implement environmental neuroscience using electroencephalography, summarising important event-related potential components and how they can be used to answer questions in climate change psychology. Challenges for the field include accurate attribution of findings, both within and between studies, the need for interdisciplinary collaboration, peer review and reporting processes.

A Computer-Based Method for the Investigation of Human Behavior in the Iterative Chicken Game

The present study develops an artificial agent that plays the iterative chicken game based on a computational model that describes human behavior in competitive social interactions in terms of fairness. The computational model we adopted in this study, named as the self-concept fairness model, decides the agent's action according to the evaluation of fairness of both opponent and self. We implemented the artificial agent in a computer program with a set of parameters adjustable by researchers. These parameters allow researchers to determine the extent to which the agent behaves aggressively or cooperatively. To demonstrate the use of the proposed method for the investigation of human behavior, we performed an experiment in which human participants played the iterative chicken game against the artificial agent. Participants were divided into two groups, each being informed to play with either a person or the computer. The behavioral analysis results showed that the proposed method can induce changes in the behavioral pattern of human players by changing the agent's behavioral pattern. Also, we found that participants tended to be more sensitive to fairness when they played with a human opponent than with a computer opponent. These results support that the artificial agent developed in this study will be useful to investigate human behavior in competitive social interactions.

Interpersonal relationships modulate outcome evaluation in a social comparison context: The pain and pleasure of intimacy

Previous research has revealed that interpersonal relationships and social comparisons play important roles in evaluating outcomes. To our knowledge, how interpersonal relationships influence the process of outcome evaluations in a social comparison context remains largely unclear. In the current study, participants engaged in a simple gambling task with an acquaintance or a stranger and received outcome feedback. Behavioral results showed that participants' satisfaction level was sensitive to the outcome of their fellow players when participants won. In this condition, the satisfaction level was greater when their fellow players won rather than lost. Moreover, the satisfaction level was greater when their friends won compared with when a stranger won. Event-related potential (ERP) results showed that when participants won, the feedback-related negativity (FRN) was more negative going for other's losses than for other's gains. Moreover, the FRN was also more negative going for a stranger's gains than a friend's gains. In contrast, in the self-loss condition, the FRN was more negative going for other's gains than for other's losses regardless of the type of interpersonal relationship. These FRN findings indicate that the experience of other's outcomes is sensitive to participants' own outcomes. Importantly, the interpersonal relationship only showed its influence when both the self and others received monetary gains. Finally, the P300 registered participants' attention resource allocation toward monetary gains for themselves and for others, which was unaffected by the interpersonal relationship. This work reveals that outcome evaluation in various social comparison contexts is sensitive to the difference in interpersonal relationship in its early stage, labeled by the FRN.

Exposure to money modulates neural responses to outcome evaluations involving social reward

Recent research suggests that exposure to monetary cues strengthens an individual's motivation to pursue monetary rewards by inducing the 'market mode' (i.e. thinking and behaving in accordance with market principles). Here, we examined the effect of market mode on social reward processes by means of event-related potentials (ERPs). Participants primed with monetary images or neutral images acted as advisors who selected one of two options for a putative advisee. Subsequently, all participants passively observed the advisee accepting or rejecting their advice and receiving a gain or loss outcome. After money priming, the feedback-related negativity (FRN) to the advisee's gain/loss outcome was larger following incorrect as compared to correct advice irrespective of whether the advice had been accepted or rejected. A smaller P3 following incorrect advice showed only when the advice was rejected. After neutral priming, the FRN was larger for incorrect relative to correct advice only when the advice had been rejected. However, the P3 was larger for correct relative to incorrect advice irrespective of the advisee's final choice. These findings suggest that the market mode facilitates early and automatic feedback processing but reduces later and controlled responding to outcomes that had been accepted.

Effortless Retaliation: the Neural Dynamics of Interpersonal Intentions in a Chicken Game Using Brain-Computer Interface

The desire for retaliation is a common response across a majority of human societies. However, the neural mechanisms underlying aggression and retaliation remain unclear. Previous studies on social intentions are confounded by a low-level response-related brain activity. Using an Electroencephalogram (EEG)-based brain–computer interface combined with the Chicken Game, our study examined the neural dynamics of aggression and retaliation after controlling for nonessential response-related neural signals. Our results show that aggression is associated with reduced alpha event-related desynchronization (alpha-ERD), indicating reduced mental effort. Moreover, retaliation and tit-for-tat strategy use are also linked with smaller alpha-ERD. Our study provides a novel method to minimize motor confounds and demonstrates that choosing aggression and retaliation is less effortful in social conflicts.

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.

Monetary payoffs modulate reciprocity expectations in outcome evaluations: An event-related potential study

Choosing cooperation or aggression relies on reciprocity preferences which refer to the tendency of an individual to return cooperative or aggressive action for cooperative or aggressive action (i.e., positive or negative reciprocity preference). The reciprocity preference is positively correlated with reciprocity expectation, wherein individuals with stronger reciprocity preferences may have higher expectations than future cooperative or aggressive behavior should be delivered by beneficiaries (positive reciprocity expectation) or victims (negative reciprocity expectation). Although previous studies have demonstrated that the presence of monetary payoffs enhances reciprocity preferences, the modulation of monetary payoffs in reciprocity expectations remains unclear. Using event-related potentials (ERPs), we examined how monetary payoffs modulated reciprocity expectations by adopting the Chicken game. Participants were asked to choose between cooperation and aggression with a putative opponent in the Chicken game involving the monetary (vs. non-monetary) payoffs. Participants' electroencephalogram (EEG) was recorded when they saw the opponent's cooperative or aggressive decision. Results showed that compared to the non-monetary payoff trials, the feedback-related negativity (FRN) effect in response to the opponent's decisions was stronger following the participant's aggressive decision in the monetary payoff trials, whereas P3 was insensitive to monetary payoffs. These findings suggest that monetary payoffs heighten expectations of negative reciprocity at the earlier and automatic outcome processing stage.

Neural processing of iterated prisoner's dilemma outcomes indicates next-round choice and speed to reciprocate cooperation

The iterated prisoner's dilemma (iPD) game is a well-established model for testing how people cooperate, and the neural processes that unfold after its distinct outcomes have been partly described. Recent theoretical models suggest evolution favors intuitive cooperation, which raises questions on the behavioral but also neural timelines involved. We studied the outcome/feedback stage of iPD rounds with electroencephalography (EEG) methods. Results showed that neural signals associated with this stage also relate to future choice, in an outcome-dependent manner: (i) after zero-gain "sucker's payoffs" (unreciprocated cooperation), a participant's decision thereafter relates to changes to the feedback-related negativity (FRN); (ii) after one-sided non-cooperation (participant wins at co-player's expense), by the P3; (iii) after mutual cooperation, by late frontal delta-band modulations. Critically, faster reciprocation behavior towards a co-player's choice to cooperate was predicted, on a single-trial basis, by players' P3 and frontal delta modulations at the immediately preceding trial. Delta-band signaling is discussed in relation to homeostatic regulation processing in the literature. The findings relate the early outcome/feedback stage to subsequent decisional processes in the iPD, providing a first neural account of the brief timelines implied in heuristic modes of cooperation.

Nudge for justice: An ERP investigation of default effects on trade-offs between equity and efficiency

Default options are an increasingly common tool used by organizations, managers, and policymakers to guide individuals' behavior. We wondered whether the known preference for default options could constitute a nudge to achieve more equitable or more efficient results. Combining with event-related potentials, we found that both the default option and distributive justice contributed significantly to decision-making. The N200s and P300s were extracted using the tensor decomposition, which showed superiority in terms of capturing multi-domain features. The results demonstrated that greater brain activity associated with conflict monitoring was elicited in the trade-off between equity and efficiency when the default could not represent a socially desirable action. Besides, participants attached more motivational/affective significance to equitable defaults than inequitable default options. Further, individuals with larger neural response differences between equitable and inequitable defaults appeared to be more inequity aversion in behavior. These findings offer a novel perspective on the role of default effects on distributive justice, while contributing to both organizational policy and practice by using the default to improve social welfare.

Procedural fairness predicts cooperative behaviour for high-self-esteem individuals but not for low-self-esteem individuals

Cooperation is vital for modern society. Previous studies showed that procedural fairness promotes cooperation; however, they mainly focused on cooperation intention, which may fail to reveal actual cooperative behaviour. Moreover, little is known regarding the personality boundary of the effect of procedural fairness on cooperation. Guided by previous findings that self-esteem increases sensitivity to procedural unfairness, we attempted to explore the moderating effect of self-esteem on the association between procedural fairness and cooperative behaviour. In Experiment 1, 160 participants' self-esteem was measured using the Rosenberg Self-Esteem Scale; procedural fairness was manipulated in two conditions, depending on whether money was allocated in an economic game by rolling the dice twice or an allocator's arbitrary choice. Cooperative behaviour was assessed using the chicken game paradigm. Experiment 2 (148 participants) aimed to replicate and extend the results of Experiment 1 using a more rigorous experimental design, in which the possible effect of outcome favourability was excluded. The results of both experiments consistently showed that procedural fairness positively predicted cooperative behaviour, and this association was significant in high-self-esteem individuals, but not in low-self-esteem individuals. These findings shed light on the vital role of self-esteem in understanding the relationship between procedural fairness and cooperative behaviour.

Cooperation moderates the impact of effort on reward valuation

Effort is valuable, but researchers have different opinions on whether effort can reduce or increase the valuation of rewards. The effect of cooperation on reward valuation also remains unclear. In this study, we conducted two experiments to examine the effect of effort on reward valuation (Experiment 1) and whether this effect can be influenced by cooperation (Experiment 2), using electroencephalogram (EEG) technology. We found that when participants worked alone, they generated a larger feedback-related negativity (FRN) amplitude for losing rewards than for gaining rewards, with more effort resulting in larger FRN amplitudes for losing rewards. However, when participants worked together with a partner, there was no significant difference between the amplitude for gaining rewards and that for losing rewards during low-effort tasks. Nevertheless, for high-effort tasks, the FRN amplitude for losing rewards was significantly larger than that for gaining rewards. Moreover, in both experiments, we found larger N1 amplitudes for gaining rewards than for losing rewards. Our ERP results suggest that in the early stage of processing, people pay extra attention to rewards, after that the effort level influences their reward valuation. In addition, cooperation regulates the reduced valuation of losing rewards only when people invest low effort.

Social value orientation modulates context-based social comparison preference in the outcome evaluation: An ERP study

Social value orientation (SVO) is a personality trait that is closely associated with social comparison preference. However, little is known about how the different types of SVO (i.e., proself vs. prosocial) modulate the behaviour and neural underpinnings of its interaction with social context. In the present study, we examined electrophysiological correlates captured when individuals with different SVOs engaged in a gambling game with two other players (a socially disliking player, person A, vs. a socially liking player, person B). Three main findings are reported in our study. 1) Social comparison effects were manifested in feedback-related negativity (FRN) (the most negative FRN was expressed in the large difference condition, and the least negative FRN was expressed in the even condition), and this effect was modulated by both the win/loss context and SVO. That is, in a self-win context, FRN exhibited a social comparison effect for both prosocials and proselfs. In the self-loss condition, only prosocials displayed this effect. 2) Both groups displayed an enhanced FRN to person A's (the disliked player's) loss compared with the FRN to A's win in the self-win context, whereas only prosocials displayed a more negative FRN to A's win compared to A's loss in the self-loss context. 3) There was a social liking effect, but not a social comparison effect, on the P300, showing that for prosocials only, winning with a socially liking player elicited an increased P300 compared to winning with a disliking player. These findings suggest that the influences of SVO on social comparison are automatic and context dependent, which is reflected by a semi-automatic FRN in which prosocials are sensitive to others' wins or losses in both the self-win and self-loss contexts, whereas proselfs are not interested in others' outcomes in the self-loss context. Furthermore, interpersonal relationships affected the P300 for prosocials when they won but had no effect on the proselfs. This work sheds light on the neural basis of outcome evaluation in multiple social contexts and its individual differences in automatic social comparison situations.

Sociality Mental Modes Modulate the Processing of Advice-Giving: An Event-Related Potentials Study

People have different motivations to get along with others in different sociality mental modes (i.e., communal mode and market mode), which might affect social decision-making. The present study examined how these two types of sociality mental modes affect the processing of advice-giving using the event-related potentials (ERPs). After primed with the communal mode and market mode, participants were instructed to decide whether or not give an advice (profitable or damnous) to a stranger without any feedback. The behavioral results showed that participants preferred to give the profitable advice to the stranger more slowly compared with the damnous advice, but this difference was only observed in the market mode condition. The ERP results indicated that participants demonstrated more negative N1 amplitude for the damnous advice compared with the profitable advice, and larger P300 was elicited in the market mode relative to both the communal mode and the control group. More importantly, participants in the market mode demonstrated larger P300 for the profitable advice than the damnous advice, whereas this difference was not observed at the communal mode and the control group. These findings are consistent with the dual-process system during decision-making and suggest that market mode may lead to deliberate calculation for costs and benefits when giving the profitable advice to others.