Trust as commodity: social value orientation affects the neural substrates of learning to cooperate

Neural markers of human aggression and cooperation are influenced by zero-sum or non-zero-sum groups

Cooperation and competition in social interaction are important to social development. There are many studies examining the neural mechanism underlying these behaviors; however, little is known about the potential role of payoff norms in social interactions. This study introduced two distinct payoff norms: zero-sum (ZS) and non-zero-sum (NZS). In the ZS group, only the player with the highest total score would receive a reward; while in the NZS group, rewards were determined by the combined total score of both players, and individual rewards were prorated according to each player's contribution to the total score. Electroencephalography was used to examine individuals' neural responses during the Chicken Game in these different groups. The behavioral findings revealed a higher rate of cooperation in the NZS group compared to the ZS group. Aggressive behaviors from opponents elicited larger feedback-related negativity (FRN) and lower P300 amplitudes in both groups. Notably, larger FRN and smaller P300 amplitudes were elicited by participants' aggressive behaviors compared to their cooperative behaviors in the ZS group, whereas larger P300 amplitudes were elicited by aggressive behaviors compared to cooperative behaviors in the NZS group. Additionally, a greater theta event-related synchronization (ERS) was observed solely when participants exhibited aggression in the NZS group. The type of group moderated the association between posterior theta-ERS and cooperative rates. Specifically, theta-ERS was negatively associated with cooperative rates in the NZS group, whereas a reversed association was found in the ZS group. These findings provide valuable insights into the neurobiological foundations of cooperation under different economic payoff norms.

Neural mechanisms of cooperation and fairness in iterative prisoner's dilemma

Cooperation is a universal human principle reflecting working with others to achieve common goals. The rational decision-making model contends that cooperation is the best strategy for maximizing benefits in an iterative prisoner's dilemma. However, the motivations for cooperation (or betrayal) are complex and diverse, and often include fairness reflections. In this study, we used functional magnetic resonance imaging to study underlying neural differences in brain regions related to fairness when people interact with an opponent who tend to cooperate or betray, at different decision-making stages. Results based on 40 university students (25 women) indicate that experiences of cooperation or betrayal affect people's fairness perception. Distinct neural activities occur in expectation, decision, and outcome phases of decisions. In the expectation phase, those in the cooperative condition exhibited increased activation in the anterior cingulate gyrus, medial superior frontal gyrus, and caudate nucleus compared to those in the uncooperative condition. During the decision phase, those in the cooperative condition showed greater activation in the middle frontal gyrus, caudate nucleus/frontal insula, inferior frontal gyrus, and cingulate gyrus compared to those in the uncooperative condition. In the outcome feedback phase, the caudate nucleus, insula, cingulate gyrus, and inferior frontal gyrus of the orbit were more active in the uncooperative condition than in the cooperative condition. Results also showed a significant correlation between caudate activity and the perception of fairness when expecting uncooperative conditions.

The anatomical structure of sex differences in trust propensity: A voxel-based morphometry study

Trust is a key component of human relationships. Sex differences in trust behavior have been elucidated by parental investment theory and social role theory, attributing men's higher trust propensity to their increased engagement in physically and socially risky activities aimed at securing additional resources. Although sex differences in trust behavior exist and the neuropsychological signatures of trust are known, the underlying anatomical structure of sex differences is still unexplored. Our study aimed to investigate the anatomical structure of sex differences in trust behavior toward strangers (i.e., trust propensity, TP) by employing voxel-based morphometry (VBM) in a sample of healthy young adults. We collected behavioral data for TP as measured with participants in the role of trustors completing the one-shot trust game (TG) with anonymous partners as trustees. We conducted primary region of interest (ROI) and exploratory whole-brain (WB) VBM analyses of high-resolution structural images to test for the association between TP and regional gray matter volume (GMV) associated with sex differences. Confirming previous studies, our behavioral results demonstrated that men trusted more than women during the one-shot TG. Our WB analysis showed a greater GMV related to TP in men than women in the precuneus (PreC), whereas our ROI analysis in regions of the default-mode network (dorsomedial prefrontal cortex [dmPFC], PreC, superior temporal gyrus) to simulate the partner's trustworthiness, central-executive network (ventrolateral PFC) to implement a calculus-based trust strategy, and action-perception network (precentral gyrus) to performance cost-benefit calculations, as proposed by a neuropsychoeconomic model of trust. Our findings advance the neuropsychological understanding of sex differences in TP, which has implications for interpersonal partnerships, financial transactions, and societal engagements.

Understanding the cognitive and neuroimaging bases underlying the detrimental impact of sleep deprivation on reciprocity

Although the impact of sleep loss on social behaviors has been widely observed in recent years, the mechanisms underpinning these impacts remain unclear. In this study, we explored the detrimental effects of sleep deprivation on reciprocity behavior as well as its underlying psychological and neuroimaging mechanisms by combining sleep manipulation, an interpersonal interactive game, computational modeling and neuroimaging. Our results suggested that after sleep deprivation, individuals showed reduced reciprocity behavior, mainly due to their reduced weights on communal concern when making social decisions. At neural level, we demonstrated that sleep deprivation's effects were observed in the precuneus (hyperactivity) and temporoparietal junction, dorsal lateral prefrontal cortex (DLPFC) (both hypoactivity), and reduced reciprocity was also accounted for by increased precuneus-thalamus connectivity and DLPFC-thalamus connectivity. Our findings contributed to the understanding of the psychological and neuroimaging bases underlying the deleterious impact of sleep deprivation on social behaviors.

Proselfs depend more on model-based than model-free learning in a non-social probabilistic state-transition task

Humans form complex societies in which we routinely engage in social decision-making regarding the allocation of resources among ourselves and others. One dimension that characterizes social decision-making in particular is whether to prioritize self-interest or respect for others-proself or prosocial. What causes this individual difference in social value orientation? Recent developments in the social dual-process theory argue that social decision-making is characterized by its underlying domain-general learning systems: the model-free and model-based systems. In line with this "learning" approach, we propose and experimentally test the hypothesis that differences in social preferences stem from which learning system is dominant in an individual. Here, we used a non-social state transition task that allowed us to assess the balance between model-free/model-based learning and investigate its relation to the social value orientations. The results showed that proselfs depended more on model-based learning, whereas prosocials depended more on model-free learning. Reward amount and reaction time analyses showed that proselfs learned the task structure earlier in the session than prosocials, reflecting their difference in model-based/model-free learning dependence. These findings support the learning hypothesis on what makes differences in social preferences and have implications for understanding the mechanisms of prosocial behavior.

Fast deliberation is related to unconditional behaviour in iterated Prisoners' Dilemma experiments

People have different preferences for what they allocate for themselves and what they allocate to others in social dilemmas. These differences result from contextual reasons, intrinsic values, and social expectations. What is still an area of debate is whether these differences can be estimated from differences in each individual's deliberation process. In this work, we analyse the participants' reaction times in three different experiments of the Iterated Prisoner's Dilemma with the Drift Diffusion Model, which links response times to the perceived difficulty of the decision task, the rate of accumulation of information (deliberation), and the intuitive attitudes towards the choices. The correlation between these results and the attitude of the participants towards the allocation of resources is then determined. We observe that individuals who allocated resources equally are correlated with more deliberation than highly cooperative or highly defective participants, who accumulate evidence more quickly to reach a decision. Also, the evidence collection is faster in fixed neighbour settings than in shuffled ones. Consequently, fast decisions do not distinguish cooperators from defectors in these experiments, but appear to separate those that are more reactive to the behaviour of others from those that act categorically.

Factors of influence in prisoner's dilemma task: a review of medical literature

The Prisoner's Dilemma (PD) is one of the most popular concepts amongst the scientific literature. The task is used in order to study different types of social interactions by giving participants the choice to defect or cooperate in a specific social setting/dilemma. This review focuses on the technical characteristics of the PD task as it is used in medical literature and describes how the different PD settings could influence the players' behaviour. We identify all the studies that have used the PD task in medical research with human participants and distinguish, following a heuristic approach, seven parameters that can differentiate a PD task, namely (a) the opponent parties' composition; (b) the type of the opponent as perceived by the players; (c) the interaction flow of the game; (d) the number of rounds; (e) the instructions narrative and options that are given to players; (f) the strategy and (g) the reward matrix and payoffs of the game. We describe how each parameter could influence the final outcome of the PD task and highlight the great variability concerning the settings of these parameters in medical research. Our aim is to point out the heterogeneity of such methods in the past literature and to assist future researchers with their methodology design.

The Prisoner's Dilemma paradigm provides a neurobiological framework for the social decision cascade

To function during social interactions, we must be able to consider and coordinate our actions with other people's perspectives. This process unfolds from decision-making, to anticipation of that decision's consequences, to feedback about those consequences, in what can be described as a "cascade" of three phases. The iterated Prisoner's Dilemma (iPD) task, an economic-exchange game used to illustrate how people achieve stable cooperation over repeated interactions, provides a framework for examining this "social decision cascade". In the present study, we examined neural activity associated with the three phases of the cascade, which can be isolated during iPD game rounds. While undergoing functional magnetic resonance imaging (fMRI), 31 adult participants made a) decisions about whether to cooperate with a co-player for a monetary reward, b) anticipated the co-player's decision, and then c) learned the co-player's decision. Across all three phases, participants recruited the temporoparietal junction (TPJ) and the dorsomedial prefrontal cortex (dmPFC), regions implicated in numerous facets of social reasoning such as perspective-taking and the judgement of intentions. Additionally, a common distributed neural network underlies both decision-making and feedback appraisal; however, differences were identified in the magnitude of recruitment between both phases. Furthermore, there was limited evidence that anticipation following the decision to defect evoked a neural signature that is distinct from the signature of anticipation following the decision to cooperate. This study is the first to delineate the neural substrates of the entire social decision cascade in the context of the iPD game.

Globalization, sustainable development, and variation in cost of power plant technologies: A perspective of developing economies

This study evaluates the sustainable power plant cost in the outlook of global power plant efficiency to reduce fossil fuel dependency and greenhouse gas emissions. For this purpose, the Global Change Assessment Model (GCAM) applied for conducting the cost assessment of power zone technologies for all principal electricity generation. This study considers the characteristics of essential factors (cement, price of resources, possible increases in employees, and metals) that affect costs. This study suggests that the cost of electricity-generating technologies significantly affects growth efficiency, reduction in production cost, and improving environmental conditions. It also suggests that the cost of electricity-generating technologies, combined with technology mixture, is the key factor behind replacing existing technology in the electricity sector. EPRI cost assessments expanded by around 30% and 50% during 2015-2016. Factors like competition amongst power plant owners, the ambiguous marketplace, production procedures, and lack of environment-related strategies have resulted in massive environmental degradation in developing economies like Pakistan. Based on empirical findings, this study recommends designing efficient technologies, which would reduce power plant costs and ensure vertical prospects related to environmental conditions in the future.

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.

Neural Signatures of Gender Differences in Interpersonal Trust

Trust plays a critical role in nearly every aspect of social life. Parental investment theory and social role theory predict that women trust less than men due to a higher sensitivity to risk and betrayal, while men trust more than women to maximize resources and to signal their willingness to lose something. However, the underlying neuropsychological underpinnings for this gender difference are still obscure. In this study, we used functional magnetic resonance imaging (fMRI) to investigate the neural signatures of gender differences in trust by simultaneously scanning 11 male and 11 female same-gender, fixed dyads who played a multi-round binary trust game with varying levels of payoff (low/moderate/high) as an indicator of social risk. Our results showed that men trusted more than women and payoff level moderated the effect of gender on trust. While men trusted the same at all payoff levels, women trusted less with higher payoff levels. This pattern was supported by our neuroimaging finding: men showed a higher activation in the left inferior frontal gyrus (ventrolateral prefrontal cortex) and right precuneus than women, indicating that men exert more effort to inhibit the information of payoff levels and to use self-referencing to infer the strategies of partners with the goal of maximizing profit. Furthermore, men showed equivalent activation in the subgenual anterior cingulate cortex across payoff levels, whereas women showed a decreased activation with increasing payoff level - indicating decreased group bonding with higher risk in women. In conclusion, our results imply that women are more sensitive to social risk while trusting, which has implications for financial interactions, interpersonal relationships, and social involvement.

A quantitative description of the transition between intuitive altruism and rational deliberation in iterated Prisoner's Dilemma experiments

What is intuitive: pro-social or anti-social behaviour? To answer this fundamental question, recent studies analyse decision times in game theory experiments under the assumption that intuitive decisions are fast and that deliberation is slow. These analyses keep track of the average time taken to make decisions under different conditions. Lacking any knowledge of the underlying dynamics, such simplistic approach might however lead to erroneous interpretations. Here we model the cognitive basis of strategic cooperative decision making using the Drift Diffusion Model to discern between deliberation and intuition and describe the evolution of the decision making in iterated Prisoner's Dilemma experiments. We find that, although initially people's intuitive decision is to cooperate, rational deliberation quickly becomes dominant over an initial intuitive bias towards cooperation, which is fostered by positive interactions as much as frustrated by a negative one. However, this initial pro-social tendency is resilient, as after a pause it resets to the same initial value. These results illustrate the new insight that can be achieved thanks to a quantitative modelling of human behavior.

Left Amygdala and Putamen Activation Modulate Emotion Driven Decisions in the Iterated Prisoner's Dilemma Game

Although economic decision-making is commonly characterized as a purely rational phenomenon, it is clear that real-world decision-making is influenced by emotions. Yet, relatively little is known about the neural correlates of this process. To explore this issue, 20 participants underwent fMRI scanning while engaged in the Prisoner's Dilemma game under partner-directed sympathy, anger and neutral emotion conditions. Participants were most and least likely to cooperate after sympathy and anger induction, respectively, with the neutral condition eliciting intermediate cooperation rates. Moreover, the sympathy condition elicited quicker responses for cooperation than defection choices, whereas this pattern was reversed in the anger and neutral conditions. Left amygdala activation showed a positive correlation with cooperation rates and self-reports of partner directed sympathy in the sympathy condition. In the anger condition, left putamen activation was positively correlated with cooperation rates and negatively correlated with self-reports of partner directed anger strength. These findings indicate that while the left amygdala activation may be indicative of emotion enhancement and increase of cooperative behavior, the left putamen may help to suppress an emotion to overcome anger and engage in cooperation.

Use of Prosocial Word Enhances the Processing of Language: Frequency Domain Analysis of Human EEG

Use of prosocial language enhances human cooperation and harmony. Previous research has shown that talking about helping, sharing and giving to others creates positive impression on others, by which individuals and governments gain public approval. So far, the value judgement of approval and disapproval in terms of prosocial or antisocial has not been investigated in the domain of neuroscience of language. Here, the influence of prosocial words towards neural adaptability for greater acceptance is examined using behavioural response mapping with electroencephalography activities of human brain. The prosocial and antisocial words employing correct and incorrect set of sentences in English are presented to participants for performing grammatical judgement task. Our results show that processing of antisocial word requires larger neurocognitive resources as compared to prosocial one, which is corroborated with our behavioural response time suggesting higher response time for antisocial than prosocial words.

The impact of trust decision-making on outcome processing: Evidence from brain potentials and neural oscillations

It may be beneficial, although risky, to decide to trust others during social interactions in daily life. The current study explored the time course of the effect of trust decisions on outcome evaluation processing using electroencephalographic (EEG) techniques. Twenty-two healthy young adults made trust or distrust decisions regarding a message they received from a stranger in a card game. The results showed that at the early stage of outcome processing, feedback-related negativity (FRN) was more negative for losses than for gains, and more importantly, this valence effect of FRN was greater for outcomes following trust decisions than distrust decisions. At the later stage, the P3 was larger for gains than for losses and for outcomes following trust decisions than distrust decisions. In addition, at both the early and late stages, differences in the mid-frontal theta power between losses and gains were also greater in the trust condition than in the distrust condition. These findings indicate that trust decisions could effectively modulate the processing of outcome evaluation at different stages. The trust effect at the early stage of outcome processing suggests that compared to distrust decisions, trust decisions result in greater motivation and expectancy to obtain positive outcomes. While the trust effect on the later stage of outcome processing suggests that individuals pay more attention and feel stronger emotional experience to the outcomes following trust decisions. This study sheds light on the neural mechanisms of trust decisions modulating outcome processing.

Reward circuitry activation reflects social preferences in the face of cognitive effort

Research at the intersection of social neuroscience and cognitive effort is an interesting new area for exploration. There is great potential to broaden our understanding of how social context and cognitive effort processes, currently addressed in disparate literatures, interact with one another. In this paper, we briefly review the literature on cognitive effort, focusing on effort-linked valuation and the gap in the literature regarding cognitive effort in the social domain. Next, we present a study designed to explore valuation processes linked to cognitive effort within the social context of an inequality manipulation. More specifically, we created monetary inequality among the participant (SELF, endowed with $50) and two confederates: one also endowed with $50 (OTHER HIGH) and another with only $5 (OTHER LOW). We then scanned participants using fMRI as they attempted to earn bonus payments for themselves and others through a cognitively effortful feedback-based learning task. Positive feedback produced significantly greater activation than negative feedback in key valuation regions, the ventral striatum (VS) and ventromedial prefrontal cortex (vmPFC), both when participants were performing the task on their own behalf and when earning rewards for others. While reward-related activity in the VS was exaggerated for SELF compared to OTHER HIGH for both positive and negative feedback, activity in the vmPFC did not distinguish between recipients in the group-level results. Furthermore, participants naturally fell into two groups: those most engaged when playing for themselves and those who reported engagement for others. While Self-Engaged participants showed differences between the SELF and both OTHER conditions in the VS and vmPFC, Other-Engaged participants only showed an attenuated response to negative feedback for OTHER HIGH compared to SELF in the VS and no differences between recipient conditions in the vmPFC. Together, this work shows the importance of individual differences and the fragility of advantageous inequality aversion in the face of cognitive effort, highlighting the need to study cognitive effort in the social domain.