The Neural Basis of Egalitarian Behavior (original) (raw)
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Neural evidence for inequality-averse social preferences
Nature, 2010
A popular hypothesis in the social sciences is that humans have social preferences to reduce inequality in outcome distributions because it has a negative impact on their experienced reward 1-3 . Although there is a large body of behavioural and anthropological evidence consistent with the predictions of these theories 1,4-6 , there is no direct neural evidence for the existence of inequalityaverse preferences. Such evidence would be especially useful because some behaviours that are consistent with a dislike for unequal outcomes could also be explained by concerns for social image 7 or reciprocity 8,9 , which do not require a direct aversion towards inequality. Here we use functional MRI to test directly for the existence of inequality-averse social preferences in the human brain. Inequality was created by recruiting pairs of subjects and giving one of them a large monetary endowment. While both subjects evaluated further monetary transfers from the experimenter to themselves and to the other participant, we measured neural responses in the ventral striatum and ventromedial prefrontal cortex, two areas that have been shown to be involved in the valuation of monetary and primary rewards in both social and non-social contexts 10-14 . Consistent with inequality-averse models of social preferences, we find that activity in these areas was more responsive to transfers to others than to self in the 'high-pay' subject, whereas the activity of the 'low-pay' subject showed the opposite pattern. These results provide direct evidence for the validity of this class of models, and also show that the brain's reward circuitry is sensitive to both advantageous and disadvantageous inequality.
Social equality in the number of choice options is represented in the ventromedial prefrontal cortex
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2014
A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found ...
Scientific Reports
We have a social preference to reduce inequity in the outcomes between oneself and others. Such a preference varies according to others. We performed functional magnetic resonance imaging during an economic game to investigate how the perceived moral traits of others modulate the neural activities that underlie inequity-aversion. The participants unilaterally allocated money to three partners (good, neutral, and bad). During presentation of the good and neutral partners, the anterior region of the rostral medial frontal cortex (arMFC) showed increased functional connectivity with the caudate head and the anterior insula, respectively. Following this, participants allocated more money to the good partner, and less to the bad partner, compared with the neutral partner. The caudate head and anterior insula showed greater activation during fair allocation to the good and unfair allocation to the neutral partners, respectively. However, these regions were silent during allocations to the bad partner. Therefore, the arMFC-caudate/insula circuit encompasses distinct neural processes that underlie inequity-aversion in monetary allocations that the different moral traits of others can modulate.
The Neural Basis of Perceived Unfairness in Economic Exchanges
Human decision making in situations of inequity has long been regarded as a competition between the sense of fairness and self-interest, primarily based on behavioral and neuroimaging studies of inequity that disfavor the actor while favoring others. Here, we use functional magnetic resonance imaging experiments to study refusals and protests using both favoring and disfavoring inequity in three economic exchange games with undercompensating, nearly equal, and overcompensating offers. Refusals of undercompensating offers recruited a heightened activity in the right dorsolateral prefrontal cortex (dlPFC). Accepting of overcompensating offers recruited significantly higher node activity in, and network activity among, the caudate, the cingulate cortex, and the thalamus. Protesting of undercompensating fixed offers activated the network consisting of the right dlPFC and the left ventrolateral prefrontal cortex and midbrain in the substantia nigra. These findings suggest that perceived fairness and social decisions are the results of coordination between evaluated fairness norms, self-interest, and reward.
On the wrong side of the trolley track: Neural correlates of relative social valuation
Social Cognitive and …, 2010
Using moral dilemmas, we (i) investigate whether stereotypes motivate people to value ingroup lives over outgroup lives and (ii) examine the neurobiological correlates of relative social valuation using fMRI. Saving ingroup members, who seem warm and competent (e.g. Americans), was most morally acceptable in the context of a dilemma where one person was killed to save five people. Extreme outgroup members, who seem neither warm nor competent (e.g. homeless), were the worst off; it was most morally acceptable to sacrifice them and least acceptable to save them. Sacrificing these low-warmth, low-competence targets to save ingroup targets, specifically, activated a neural network associated with resolving complex tradeoffs: medial PFC (BA 9, extending caudally to include ACC), left lateral OFC (BA 47) and left dorsolateral PFC (BA 10). These brain regions were recruited for dilemmas that participants ultimately rated as relatively more acceptable. We propose that participants, though ambivalent, overrode general aversion to these tradeoffs when the cost of sacrificing a low-warmth, low-competence target was pitted against the benefit of saving ingroup targets. Moral decisions are not made in a vacuum; intergroup biases and stereotypes weigh heavily on neural systems implicated in moral decision making.
A functional brain imaging study on the neural correlates of altruism in social decision-making
An fMRI study was conducted to explore the neural basis of altruism in social decision-making. The participants were confronted with a non-monetary version of the Prisoner's Dilemma which is one of the earliest games developed in game theory. They could make a choice between that which would lead to their own benefit, but to the harm of another person, and one which denies one's own benefit but would be in the interest of the other person. A comparison between these social problems and a set of matched non-social problems (in which no other person was involved) revealed that a complex neural network of cortical and sub-cortical brain areas is involved in making altruistic or selfish decisions. The findings indicate that the decision to behave altruistically relies on the interactions between cognitive control processes in prefrontal cortex and emotional control processes in the amygdala.
Inequality signals in dorsolateral prefrontal cortex inform social preference models
Social cognitive and affective neuroscience, 2018
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 mo...
Scientific reports, 2016
Social value orientations (SVOs) are economic preferences for the distribution of resources - prosocial individuals are more cooperative and egalitarian than are proselfs. Despite the social and economic implications of SVOs, no systematic studies have examined their neural correlates. We investigated the amygdala and dorsolateral prefrontal cortex (DLPFC) structures and functions in prosocials and proselfs by functional magnetic resonance imaging and evaluated cooperative behavior in the Prisoner's Dilemma game. We found for the first time that amygdala volume was larger in prosocials and positively correlated with cooperation, while DLPFC volume was larger in proselfs and negatively correlated with cooperation. Proselfs' decisions were marked by strong DLPFC and weak amygdala activity, and prosocials' decisions were marked by strong amygdala activity, with the DLPFC signal increasing only in defection. Our findings suggest that proselfs' decisions are controlled by...
Unfair? It depends: neural correlates of fairness in social context
Social cognitive and affective neuroscience, 2010
Fairness is a key concept in social interactions and is influenced by intentionality considerations. In this functional magnetic resonance imaging study, we investigated the neural correlates of fairness by focusing on responder behavior to unfair offers in an Ultimatum Game paradigm with conditions that differed in their intentionality constraints. Brain activity underlying rejection vs acceptance of unfair offers appeared highly dependent on intentionality. Rejection of unfair offers when the proposer had no-alternative as well as acceptance of offers when the proposer had a fair- or hyperfair-alternative was associated with activation in a network of regions including the insula and the dorsal medial prefrontal cortex. These activations were interpreted as neural responses to norm violations because they were mostly involved when behavior was inconsistent with socially accepted behavior patterns. Rejection of unfair offers in the no-alternative condition further resulted in activ...
Diminishing Reciprocal Fairness by Disrupting the Right Prefrontal Cortex
Science, 2006
Humans restrain self-interest with moral and social values. They are the only species known to exhibit reciprocal fairness, which implies the punishment of other individuals' unfair behaviors, even if it hurts the punisher's economic self-interest. Reciprocal fairness has been demonstrated in the Ultimatum Game, where players often reject their bargaining partner's unfair offers. Despite progress in recent years, however, little is known about how the human brain limits the impact of selfish motives and implements fair behavior. Here we show that disruption of the right, but not the left, dorsolateral prefrontal cortex (DLPFC) by low-frequency repetitive transcranial magnetic stimulation substantially reduces subjects' willingness to reject their partners' intentionally unfair offers, which suggests that subjects are less able to resist the economic temptation to accept these offers. Importantly, however, subjects still judge such offers as very unfair, which indicates that the right DLPFC plays a key role in the implementation of fairness-related behaviors.