Oxytocin modulates cooperation within and competition between groups: an integrative review and research agenda

Threatening joy: approach and avoidance reactions to emotions are influenced by the group membership of the expresser

It has been repeatedly stated that approach and avoidance reactions to emotional faces are triggered by the intention signalled by the emotion. This line of thought suggests that each emotion signals a specific intention triggering a specific behavioural reaction. However, empirical results examining this assumption are inconsistent, suggesting that it might be too short-sighted. We hypothesise that the same emotional expression can signal different social messages and, therefore, trigger different reactions; which social message is signalled by an emotional expression should be influenced by moderating variables, such as the group membership of the expresser. In two experiments, we show that group membership influences approach and avoidance reactions to emotional expressions: Emotions (fear and happiness) expressed by in-group members elicited concordant behaviour, whereas emotions expressed by out-group members activated the reverse pattern. A third experiment, in which participants directly evaluated smiling and fearful individuals resembling in-group and out-group members supported this result.

Genes underlying altruism

William D. Hamilton postulated the existence of 'genes underlying altruism', under the rubric of inclusive fitness theory, a half-century ago. Such genes are now poised for discovery. In this article, we develop a set of intuitive criteria for the recognition and analysis of genes for altruism and describe the first candidate genes affecting altruism from social insects and humans. We also provide evidence from a human population for genetically based trade-offs, underlain by oxytocin-system polymorphisms, between alleles for altruism and alleles for non-social cognition. Such trade-offs between self-oriented and altruistic behaviour may influence the evolution of phenotypic diversity across all social animals.

Effects of oxytocin on behavioral and ERP measures of recognition memory for own-race and other-race faces in women and men

Oxytocin has been shown to affect human social information processing including recognition memory for faces. Here we investigated the neural processes underlying the effect of oxytocin on memorizing own-race and other-race faces in men and women. In a placebo-controlled, double-blind, between-subject study, participants received either oxytocin or placebo before studying own-race and other-race faces. We recorded event-related potentials (ERPs) during both the study and recognition phase to investigate neural correlates of oxytocin's effect on memory encoding, memory retrieval, and perception. Oxytocin increased the accuracy of familiarity judgments in the recognition test. Neural correlates for this effect were found in ERPs related to memory encoding and retrieval but not perception. In contrast to its facilitating effects on familiarity, oxytocin impaired recollection judgments, but in men only. Oxytocin did not differentially affect own-race and other-race faces. This study shows that oxytocin influences memory, but not perceptual processes, in a face recognition task and is the first to reveal sex differences in the effect of oxytocin on face memory. Contrary to recent findings in oxytocin and moral decision making, oxytocin did not preferentially improve memory for own-race faces.

Antiaggressive activity of central oxytocin in male rats

RATIONALE

A substantial body of research suggests that the neuropeptide oxytocin promotes social affiliative behaviors in a wide range of animals including humans. However, its antiaggressive action has not been unequivocally demonstrated in male laboratory rodents.

OBJECTIVE

Our primary goal was to examine the putative serenic effect of oxytocin in a feral strain (wild type Groningen, WTG) of rats that generally show a much broader variation and higher levels of intermale aggression than commonly used laboratory strains of rats.

METHODS

Resident animals were intracerebroventricularly (icv) administered with different doses of synthetic oxytocin and oxytocin receptor antagonist, alone and in combination, in order to manipulate brain oxytocin functioning and to assess their behavioral response to an intruder.

RESULTS

Our data clearly demonstrate that acute icv administered oxytocin produces dose-dependent and receptor-selective changes in social behavior, reducing aggression and potentiating social exploration. These antiaggressive effects are stronger in the more offensive rats. On the other hand, administration of an oxytocin receptor antagonist tends to increase (nonsignificantly) aggression only in low-medium aggressive animals.

CONCLUSIONS

These results suggest that transiently enhancing brain oxytocin function has potent antiaggressive effects, whereas its attenuation tends to enhance aggressiveness. In addition, a possible inverse relationship between trait aggression and endogenous oxytocinergic signaling is revealed. Overall, this study emphasizes the importance of brain oxytocinergic signaling for regulating intermale offensive aggression. This study supports the suggestion that oxytocin receptor agonists could clinically be useful for curbing heightened aggression seen in a range of neuropsychiatric disorders like antisocial personality disorder, autism, and addiction.

Designing an Adaptive Approach for the Real-Time Assessment and Augmentation of Performance of Cyber Analyst Teams

Full-spectrum cyber operations, including both Cyber Network Attack and Cyber Network Defense, place enormous cognitive demands on operators and teams. When demands are too high or tasks are not properly allocated, performance degrades, and missions may fail. A thorough, real-time evaluation of the state of the individual and the team would be an effective approach to avoiding operator overload. We describe an approach that supports the real-time assessment and augmentation of team performance. First, the physiological and affective state and the behavioral performance of individual operators is measured by fusing data from individual sensors. Signals from individual operators are then fused to enable a comprehensive and holistic characterization of team performance. Advanced modeling techniques are then implemented to compare current team performance with optimal levels of performance. Finally, augmentation strategies are recommended to optimize performance of cyber teams.

Oxytocin differentially modulates compromise and competitive approach but not withdrawal to antagonists from own vs. rivaling other groups

In humans, oxytocin promotes cognitive and motivational tendencies that benefit the groups on which humans depend for their survival and prosperity. Here we examined decision making in an incentivized two-player poker game with either an in-group or out-group antagonist. Sixty nine healthy males received 24 IU oxytocin or matching placebo, and played four rounds of a simplified poker game. On each round they received either low or high value cards to create differences in competitive strength, and then responded to a bet placed by their (simulated) (in-group or out-group) antagonist. Under placebo, participants withdrew and competed depending on their own (low vs. high) competitive strength, regardless of their antagonist's group membership. Under oxytocin, however, participants settled more and competed less with an in-group as compared to an out-group antagonist; withdrawal was unaffected by group membership. We conclude that oxytocin sensitizes humans to the group membership of their interaction partner, rendering them relatively more benevolent and less competitive towards those seen as belonging to their own group. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Oxytocin pathways and the evolution of human behavior

This review examines the hypothesis that oxytocin pathways--which include the neuropeptide oxytocin, the related peptide vasopressin, and their receptors--are at the center of physiological and genetic systems that permitted the evolution of the human nervous system and allowed the expression of contemporary human sociality. Unique actions of oxytocin, including the facilitation of birth, lactation, maternal behavior, genetic regulation of the growth of the neocortex, and the maintenance of the blood supply to the cortex, may have been necessary for encephalization. Peptide-facilitated attachment also allows the extended periods of nurture necessary for the emergence of human intellectual development. In general, oxytocin acts to allow the high levels of social sensitivity and attunement necessary for human sociality and for rearing a human child. Under optimal conditions oxytocin may create an emotional sense of safety. Oxytocin dynamically moderates the autonomic nervous system, and effects of oxytocin on vagal pathways, as well as the antioxidant and anti-inflammatory effects of this peptide, help to explain the pervasive adaptive consequences of social behavior for emotional and physical health.

Economic and evolutionary hypotheses for cross-population variation in parochialism

Human populations differ reliably in the degree to which people favor family, friends, and community members over strangers and outsiders. In the last decade, researchers have begun to propose several economic and evolutionary hypotheses for these cross-population differences in parochialism. In this paper, we outline major current theories and review recent attempts to test them. We also discuss the key methodological challenges in assessing these diverse economic and evolutionary theories for cross-population differences in parochialism.

Why social attachment and oxytocin protect against addiction and stress: Insights from the dynamics between ventral and dorsal corticostriatal systems

The present article advances a neurobiological model of the reciprocal associations between social attachment and drug abuse, and social attachment and chronic stress, as overlapping systems are involved in stress coping and social attachment. In terms of coping, responding to a novel stressor or challenge involves initial novelty processing and activation of learning mechanisms that allow habituation to the stressor through familiarization. Similarly, social attachments are initially formed by being attracted by rewarding properties of an as-yet novel individual, and subsequently developing feelings of attachment towards the familiarized individual. Attachment and familiarization increase the availability of "internal working models" for the control of behavior and emotion, which may explain why secure attachments are associated with increased resilience in the face of stress, accompanied by less reactive reward responding (i.e., increased resilience against drug addiction). The present article seeks to illuminate the role of the neuropeptide oxytocin, which may be involved in the overlapping mechanisms of stable attachment formation and stress coping by shifting processing from novelty and reward seeking to appreciation of familiarity. Oxytocin may accomplish this by facilitating a ventral-to-dorsal shift in activation in corticostriatal loops, which produces a shift from a reactive reward drive (wanting) to stable appreciation of familiar social aspects ("liking" or "loving"). The authors suggest that through dopaminergic, serotonergic and endogenous opioid mechanisms, oxytocin is involved in shifting the balance between wanting and liking in corticostriatal loops by facilitating consolidation of social information from ventral reactive reward systems to dorsal internal working models that aid in prospectively selecting optimal actions in the future, increasing resilience in the face of stress and addiction.

Does intranasal oxytocin promote prosocial behavior to an excluded fellow player? A randomized-controlled trial with Cyberball

The neuropeptide oxytocin has been shown to stimulate prosocial behavior. However, recent studies indicate that adverse early caregiving experiences may moderate the positive effects of oxytocin. In this double blind randomized-controlled trial we investigated the effects of oxytocin on prosocial behavior during a virtual ball-tossing game called Cyberball. We examined the influence of oxytocin on prosocial helping behavior toward a socially excluded person who was known to the participant, taking into account early caregiving experiences and the emotional facial expression of the excluded person as potential moderators. Participants were 54 women who received a nasal spray containing either 16IU of oxytocin or a placebo and had reported how often their mother used love withdrawal as a disciplinary strategy involving withholding love and affection after a failure or misbehavior. We found that participants compensated for other players' ostracism by throwing the ball more often toward the excluded player. Oxytocin administration further increased the number of ball throws toward the excluded person, but only in individuals who experienced low levels of maternal love withdrawal. The facial expression of the excluded person did not affect prosocial helping behavior and did not moderate the effects of oxytocin. Our findings indicate that the positive effects of oxytocin on prosocial behavior toward a victim of social exclusion are limited to individuals with supportive family backgrounds.

Oxytocin eliminates the own-race bias in face recognition memory

The neuropeptide Oxytocin influences a number of social behaviors, including processing of faces. We examined whether Oxytocin facilitates the processing of out-group faces and reduce the own-race bias (ORB). The ORB is a robust phenomenon characterized by poor recognition memory of other-race faces compared to the same-race faces. In Experiment 1, participants received intranasal solutions of Oxytocin or placebo prior to viewing White and Black faces. On a subsequent recognition test, whereas in the placebo condition the same-race faces were better recognized than other-race faces, in the Oxytocin condition Black and White faces were equally well recognized, effectively eliminating the ORB. In Experiment 2, Oxytocin was administered after the study phase. The ORB resulted, but Oxytocin did not significantly reduce the effect. This study is the first to show that Oxytocin can enhance face memory of out-group members and underscore the importance of social encoding mechanisms underlying the own-race bias. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Effects of intranasal oxytocin prior to encoding and retrieval on recognition memory

RATIONALE

The neuropeptide oxytocin (OXT) has been shown to modulate a variety of human social behaviors. However, little is known about its impact on emotional memory processing. Previous research demonstrated both memory-enhancing and memory-impairing oxytocinergic effects.

METHODS

We investigated the influence of a single (prior to encoding) and a repeated (prior to encoding and retrieval) intranasal administration of OXT on recognition memory for stimuli taken from the International Affective Picture System. In addition, we assessed the interaction of emotion regulation during encoding and OXT-induced memory effects. In a double-blind, placebo-controlled design, 80 healthy young males performed an emotion regulation task followed by a surprising recognition memory task after 60 min.

RESULTS

Results show that repeated OXT administration significantly improved memory certainty for negative social stimuli. Regarding the influence of emotion regulation, the promnestic effect of OXT was more pronounced when participants had been instructed to increase their negative emotions during encoding.

CONCLUSIONS

Our findings indicate that OXT facilitates the processing of negative social stimuli during memory encoding and retrieval, possibly by enhancing the perception of aversive aspects in social situations.

A role for autonomic cardiac control in the effects of oxytocin on social behavior and psychiatric illness

Cumulative evidence over the last decade indicates that intranasally administered oxytocin (OT) has a major impact on social behavior and cognition. In parallel, researchers have also highlighted the effects of OT on cardiovascular (CV) and autonomic nervous system (ANS) regulation. Taken at face value, these two streams of research appear largely unrelated. However, another line of evidence highlights a key role for autonomic cardiac control in social behavior and cognition. In this review, we suggest that autonomic cardiac control may moderate the relationship between OT and social behavior. We also highlight the importance of autonomic cardiac control in psychiatric disorders of social dysfunction and suggest that heart rate variability (HRV)-an index of autonomic cardiac control-may play a key role in patient response in treatment trials of OT.

Medial amygdala lesions modify aggressive behavior and immediate early gene expression in oxytocin and vasopressin neurons during intermale exposure

The medial amygdala and neuropeptides oxytocin (OXT) and vasopressin (VSP) have been associated aggressive behavior regulation. However, the specific mechanism involved in OXT and VSP modulation in distinct brain regions during hostile intermale aggressive behavior is undetermined. A retrograde tracer mouse model was employed using male C57BL/6 mice injected with rhodamine-conjugated latex microsphere suspensions in the right hypothalamic paraventricular nucleus. Adult male C57BL/6 mice (aged 14-16 weeks) were subjected to resident-intruder testing using juvenile intruder mice (aged 3 weeks) or adult intruder mice (aged 8 weeks). Following exposure, Fos protein expression was increased in the medial amygdala neurons of resident mice receiving the retrograde tracer. Thus, medial amygdala neurons projecting to or localized in the vicinity of the hypothalamic paraventricular nucleus showed immediate early gene (IEG) expression following resident-intruder testing that was considered an indirect marker of activation. Additionally, intermale aggression-related behaviors were inhibited or modified by exposure to juvenile or adult intruders, respectively, in mice that underwent medial amygdala lesioning. Furthermore, Fos protein expression in OXT-positive neurons was attenuated. Thus, ablation of medial amygdala neurons prevented immediate early gene expression in OXT- and VSP-positive neurons in the hypothalamus, bed nucleus of stria terminalis, and medial preoptic area during intermale exposure. These findings indicate that the medial amygdala likely modulates hostile aggressive behavior associated with immediate early gene expression in OXT and VSP neurons in specific brain areas, which may actually be instrumental in beneficial social interaction-related aggressive responses associated with mating, territorial defense, and offspring protection.

Oxytocin-Motivated Ally Selection is Moderated by Fetal Testosterone Exposure and Empathic Concern

In humans, the hypothalamic neuropeptide oxytocin shifts the individual’s focus on self-interest toward group-serving cognitions and decision-making. Here we examine this general tendency in the context of group formation, where individuals included into their group (or not) 18 targets morphed as having low or high-threat potential (with high-threat targets being beneficial to group-interests but potentially hurting the recruiter’s self-interest). Ninety healthy males self-administered oxytocin or placebo in a randomized double-blind, placebo-controlled study design, had their hands scanned to derive fetal testosterone vs. estradiol exposure from their 2D:4D ratio, and self-reported on their chronic empathic concern. Multilevel regression models revealed that when given oxytocin rather than placebo, individuals with low fetal testosterone priming included low-threat targets more and high-threat targets (somewhat) less. Individuals with high fetal testosterone (i.e., low estradiol) exposure, however, included high-threat targets more, and low-threat targets less when given oxytocin rather than placebo. Second, when given oxytocin rather than placebo, individuals with low empathic concern included low-threat targets more and high-threat targets less. Individuals with high empathic concern, however, included high-threat targets more, and low-threat targets less when given oxytocin rather than placebo. We conclude that oxytocin shifts the individual’s focus from self to group-serving cognition and decision-making, and that these tendencies are stronger for males with high rather than low fetal testosterone vs. estradiol exposure, and high rather than low empathic concern. Implications and avenues for future research are discussed.

Oxytocin modulates social distance between males and females

In humans, interpersonal romantic attraction and the subsequent development of monogamous pair-bonds is substantially predicted by influential impressions formed during first encounters. The prosocial neuropeptide oxytocin (OXT) has been identified as a key facilitator of both interpersonal attraction and the formation of parental attachment. However, whether OXT contributes to the maintenance of monogamous bonds after they have been formed is unclear. In this randomized placebo-controlled trial, we provide the first behavioral evidence that the intranasal administration of OXT stimulates men in a monogamous relationship, but not single ones, to keep a much greater distance (~10-15 cm) between themselves and an attractive woman during a first encounter. This avoidance of close personal proximity occurred in the physical presence of female but not male experimenters and was independent of gaze direction and whether the female experimenter or the subject was moving. We further confirmed this unexpected finding using a photograph-based approach/avoidance task that showed again that OXT only stimulated men in a monogamous relationship to approach pictures of attractive women more slowly. Importantly, these changes cannot be attributed to OXT altering the attitude of monogamous men toward attractive women or their judgments of and arousal by pictures of them. Together, our results suggest that where OXT release is stimulated during a monogamous relationship, it may additionally promote its maintenance by making men avoid signaling romantic interest to other women through close-approach behavior during social encounters. In this way, OXT may help to promote fidelity within monogamous human relationships.

The Cooperative Brain

Cooperation is essential for the functioning of human societies. To better understand how cooperation both succeeds and fails, recent research in cognitive neuroscience has begun to explore novel paradigms to examine how cooperative mechanisms may be encoded in the brain. By combining functional neuroimaging techniques with simple but realistic tasks adapted from experimental economics, this approach allows for the discrimination and modeling of processes that are important in cooperative behavior. Here, we review evidence demonstrating that many of the processes underlying cooperation overlap with rather fundamental brain mechanisms, such as, for example, those involved in reward, punishment and learning. In addition, we review how social expectations induced by an interactive context and the experience of social emotions may influence cooperation and its associated underlying neural circuitry, and we describe factors that appear important for generating cooperation, such as the provision of incentives. These findings illustrate how cognitive neuroscience can contribute to the development of more accurate, brain-based, models of cooperative decision making.

Twenty-five lessons from computational neuromodulation

Neural processing faces three rather different, and perniciously tied, communication problems. First, computation is radically distributed, yet point-to-point interconnections are limited. Second, the bulk of these connections are semantically uniform, lacking differentiation at their targets that could tag particular sorts of information. Third, the brain's structure is relatively fixed, and yet different sorts of input, forms of processing, and rules for determining the output are appropriate under different, and possibly rapidly changing, conditions. Neuromodulators address these problems by their multifarious and broad distribution, by enjoying specialized receptor types in partially specific anatomical arrangements, and by their ability to mold the activity and sensitivity of neurons and the strength and plasticity of their synapses. Here, I offer a computationally focused review of algorithmic and implementational motifs associated with neuromodulators, using decision making in the face of uncertainty as a running example.

Elevated Salivary Levels of Oxytocin Persist More than 7 h after Intranasal Administration

We addressed the question how long salivary oxytocin levels remain elevated after intranasal administration, and whether it makes a difference when 16 or 24 IU of oxytocin administration is used. Oxytocin levels were measured in saliva samples collected from 46 female participants right before intranasal administration (at 9:30 a.m.) of 16 IU (n = 18) or 24 IU (n = 10) of oxytocin, or a placebo (n = 18), and each hour after administration, for 7 h in total. Oxytocin levels did not differ among conditions before use of the nasal spray. Salivary oxytocin levels in the placebo group showed high stability across the day. After oxytocin administration oxytocin levels markedly increased, they peaked around 1 h after administration, and were still significantly elevated 7 h after administration. The amount of oxytocin (16 or 24 IU) did not make a difference for oxytocin levels. The increase of oxytocin levels for at least 7 h shows how effective intranasal administration of oxytocin is. Our findings may raise ethical questions about potentially persisting behavioral effects after participants have left the lab setting. More research into the long-term neurological and behavioral effects of sniffs of oxytocin is urgently needed.

The influence of oxytocin administration on responses to infant faces and potential moderation by OXTR genotype

RATIONALE

Oxytocin is a neuropeptide that is associated with increases in social affiliative behaviors, particularly toward infants. However, no previous study has investigated healthy adults' responses to infant faces following oxytocin administration. In addition, given that preliminary evidence suggests that a single-nucleotide polymorphism of the oxytocin receptor (OXTR) gene, rs53576, may influence behaviors associated with parental sensitivity, we assessed whether such responses vary according to OXTR rs53576 genotype.

OBJECTIVES

The present study assessed the effects of intranasally administered oxytocin and OXTR genotype on human adults' preferences for infant faces.

METHODS

A double-blind, between-groups design was used, with 57 genotyped volunteers randomly assigned to receive intranasally administered oxytocin or placebo. Fifty minutes following the administration of oxytocin or placebo, participants viewed infants' and adults' faces showing neutral expressions and assessed how appealing they found each face.

RESULTS

Infants' faces were more strongly preferred following oxytocin inhalation relative to placebo. When participants were separated according to genotype, this effect was only observed for participants homozygous for the rs53576G allele. Parallel effects were not seen for adults' faces.

CONCLUSIONS

The present results are consistent with the hypothesis that acute oxytocin administration increases sensitivity to reward-relevant features of infants and/or reduces sensitivity to their aversive properties. The results are also consistent with suggestions of more efficient oxytocinergic function in rs53576G homozygotes.

Neurophysiological mechanisms underlying affiliative social behavior: insights from comparative research

Humans are intensely social animals, and healthy social relationships are vital for proper mental health (see Lim and Young, 2006). By using animal models, the behavior, mental, and physiological processes of humans can be understood at a level that cannot be attained by studying human behavior and the human brain alone. The goals of this review are threefold. First, we define affiliative social behavior and describe the primary relationship types in which affiliative relationships are most readily observed--the mother-infant bond and pair-bonding. Second, we summarize neurophysiological studies that have investigated the role of neurohypophyseal nanopeptides (oxytocin and vasopressin) and the catecholamine dopamine in regulating affiliative social behavior and the implications of said research for our understanding of human social behavior. Finally, we discuss the merits and limitations of the using a comparative approach to enhance our understanding of the mechanisms underlying human affiliative social behavior.

Oxytocin motivates non-cooperation in intergroup conflict to protect vulnerable in-group members

Intergroup conflict is often driven by an individual's motivation to protect oneself and fellow group members against the threat of out-group aggression, including the tendency to pre-empt out-group threat through a competitive approach. Here we link such defense-motivated competition to oxytocin, a hypothalamic neuropeptide involved in reproduction and social bonding. An intergroup conflict game was developed to disentangle whether oxytocin motivates competitive approach to protect (i) immediate self-interest, (ii) vulnerable in-group members, or (iii) both. Males self-administered oxytocin or placebo (double-blind placebo-controlled) and made decisions with financial consequences to themselves, their fellow in-group members, and a competing out-group. Game payoffs were manipulated between-subjects so that non-cooperation by the out-group had high vs. low impact on personal payoff (personal vulnerability), and high vs. low impact on payoff to fellow in-group members (in-group vulnerability). When personal vulnerability was high, non-cooperation was unaffected by treatment and in-group vulnerability. When personal vulnerability was low, however, in-group vulnerability motivated non-cooperation but only when males received oxytocin. Oxytocin fuels a defense-motivated competitive approach to protect vulnerable group members, even when personal fate is not at stake.

Religious thought and behavior

While earlier approaches to religious thought and practice searched for 'magic bullet' approaches to explain religious thought and behavior, seeing it as an example of irrationality, illusion, integrative force, symbolism, or false explanations of origins, cognitive scientific approaches have suggested that we see it rather as an aggregate of the products of various cognitive mechanisms. Studies in the cognitive science of religion, informed by experimental work, have converged on a standard model of explaining religious thought and behavior by focussing on the role of minimally counter-intuitive concepts, agent and animacy detection, ritual representations, notions of contagion and contamination avoidance, theory of mind, coalitions, and moral intuitions. WIREs Cogn Sci 2012 doi: 10.1002/wcs.1189 For further resources related to this article, please visit the WIREs website.

The other side of the coin: oxytocin decreases the adherence to fairness norms

Oxytocin (OXT) has been implicated in prosocial behaviors such as trust and generosity. Yet, these effects appear to strongly depend on characteristics of the situation and the people with whom we interact or make decisions. Norms and rules can facilitate and guide our actions, with fairness being a particularly salient and fundamental norm. The current study investigated the effects of intranasal OXT administration on fairness considerations in social decision-making in a double-blind, placebo-controlled within-subject design. After having received 24 IU of OXT or placebo (PLC), participants completed a one-shot Dictator Game (DG) and played the role of the responder in a modified version of the Ultimatum Game (UG), in which an unfair offer of eight coins for the proposer and two coins for the responder is paired with either a fair-(5:5) or no-alternative (8:2). Rejection rates were higher when a fair alternative had been available than when there was no alternative to an unfair offer. Importantly, OXT did not de-or increase rejection rates overall, but reduced the sensitivity to contextual fairness, i.e., the context of alternatives in which an offer was made. As dictators, participants allocated less coins to the recipient when given OXT than when given PLC, indicating a decline in generosity. These results suggest that OXT decreases the adherence to fairness norms in social settings where others are likely to be perceived as not belonging to one's ingroup. While our findings do not support the prosocial conception of OXT, they corroborate recent ideas that the effects of OXT are more nuanced than assumed in the past.