Influence Of In-group Culture And Friendships On Oxytocin’s Facilitation Of Social Reward

The neuropeptide oxytocin(OXT),a pituitary peptide synthesized by the hypothalamus that promotes parturition and lactation.Studies have demonstrated that OXT can regulate individual social cognitive and emotional behaviors,as well as facilitate social interaction in different contexts,which have raised the possibility of it being used therapeutically for disorders such as anxiety or autism,depression and posttraumatic stress.The effects of OXT depend to a large extent on the experimental tasks and contexts used,as well as subject characteristics such as sex,personality and personal experience.The background research on OXT is summarized and the primary focus is on the sex and contextual effects of OXT as the foundation of the new studies described here.In an attempt to verify the contextual effects of OXT two experiments were designed investigating its modulation of reward processing under different conditions including inter-group relationships and individual relationships.The two studies involve a combination of behavior,neuropharmacology and brain imaging.and the classic psychological experimental paradigms were used to explore the effects of OXT on social reward processing and its corresponding neural mechanisms.Study 1 explores the effect of OXT on the reward processing and the moderating effect of in-group culture.The intergroup bias generally includes the favoritism towards members of an in-group and derogation of members of out-groups.Importantly,intranasal OXT administration can increase in-group favoritism and ethnocentrism in men.However,whether such effects also occur in women and can extend beyond people to include national symbols and consumer products is unclear.In this study,we investigated the effect of intranasal OXT on likeability and arousal ratings for pictures depicting people or national symbols/ consumer products from both in-groups and out-groups.In a between-subject,double-blind placebo-controlled design 51 adult Chinese males and female college students were recruited.Subjects were randomly administrated with 24 international units(IU)of OXT(experimental group)or placebo(PLC,control group)intranasally.Before the formal experiment,the subjects completed a series of questionnaires.45 minutes after treatment the formal experiment started with behavioral ratings of different pictures.The subjects were presented with a series of pictures showing people(social)or things(non-social)from both strong and weak in-groups and corresponding out-groups.The subjects were instructed to evaluate social or non-social stimuli in terms of liking,arousal and familiarity using a 9-point scale.To assess whether OXT had a lasting effect,the subjects also had a surprise test using same procedure one week later without any further administration.Results showed for the first time that OXT selectively increased the likability for Chinese social stimuli and the national flag,but had no effect on ratings of other Chinese cultural symbols,companies and consumer products.This effect of OXT was independent of the sex of the subjects and remained stable after a week.No other OXT effects were found.This finding further supports a role of OXT in promoting an intergroup bias is mainly by increasing in-group favoritism rather than out-group derogation.However,we do not know whether this effect of OXT is limited to an influence on intergroup relations or can also be extended to individual relationships such as friendship.A further study was therefore designed to investigate this problem.Study 2 investigated the effects of OXT on social reward processing in the context of the regulation of individual friendships.Individuals are highly dependent on their social relationships and are influenced by interpersonal relationships in the processing of social information.The neuropeptide OXT may facilitate social interactions either by increasing their rewarding experience or by attenuating anxiety,although effects can be sex-and attachment-style dependent.The current study therefore examined whether intranasal-OXT differentially modulated the emotional impact of social sharing and associated neural processing.A total of 128 pairs of same-sex friends(256 subjects in total)completed a social sharing paradigm simultaneously in a double-blind,placebocontrolled,between-subject design with one friend inside an MRI scanner and the other in a behavioral testing room.Subjects were randomly assigned to either the experimental group or control group and were given 40 IU of OXT or PLC.Before the formal experiment,subjects completed several questionnaires.In the formal experiment,participants were presented with emotional stimuli of either positive,neutral or negative valence which they were informed that they were either experiencing alone(control condition)or with a stranger(stranger sharing condition)or with their friend(friend sharing condition)in a randomized event-related design.The subjects were instructed to evaluate all the pictures in terms of valence and arousal using a 9-point scale.The results showed that,OXT administration increased positive ratings for sharing stimuli with their friend in women,but not men,particularly in the subjects who completed the task in the more stressful environment of the MRI scanner.Corresponding neuroimaging results indicated that OXT decreased both amygdala and insula activity as well as their functional connectivity in women when they shared with friends but had the opposite effect in men.On the other hand,OXT did not enhance responses in brain reward circuitry.In the PLC treated group amygdala responses in women when they shared pictures with their friend were positively associated with attachment anxiety and OXT uncoupled this.Thus,OXT effects in this context may be due more to reduced anxiety when sharing with a friend than to enhanced social reward,particularly in individuals with higher attachment anxiety.Taken together,these findings demonstrate that OXT can enhance both in-group bias for social stimuli and sharing positive experiences with friends.However,while the ingroup effects are sex-independent those in relation to sharing with friends are restricted to female subjects and associated with sex-dependent patterns of neural activation and functional connectivity in brain regions primarily associated with anxiety rather than reward.Furthermore,neural effects of OXT in women were modulated by their attachment anxiety.Thus,effects of OXT on social cognitive behavior are context-and individual-dependent and these new findings highlight the need for additional research on the complex interactions between these factors.