내집단 유대가 공정성을 억제하는 근거
뇌영상·행동 연구들은
① 가족·친밀한 내집단 유대가 촉발하는 옥시토신(“사랑 호르몬”) 분비가 알코올 섭취와 유사하게 전전두피질 억제-계(GABA) 회로를 누르며 일시적 ‘취한 듯한’ 저억제 상태를 만들고[1][2][3][4],
② 그때 공정성 판단을 담당하는 전전두피질·전측섬엽(insula)·P300 네트워크의 반응이 줄어들어 내집단 구성원의 불공정 행위를 더 관대하게 받아들인다는 사실을 제시한다[5][6][7][8][9].
따라서 현재 뇌과학 데이터는 내집단 유대가 공정성을 억제한다는 결론을 지지한다.
1. 강한 가족·내집단 유대가 ‘취한 듯한’ 뇌 상태를 유발하는 근거
옥시토신-알코올 작용 유사성
옥시토신 분무는 알코올과 마찬가지로 전전두피질과 변연계 GABA 신호를 감소시켜 불안·억제·위험회피를 낮춘다[1][2].
두 물질 모두 사회적 자신감·공격성·집단편애를 동시에 높이며, “Dutch courage(술 용기)” 현상과 동일한 효과를 실험실에서 재현했다[3][4].
동물‧인간 교차 연구
쥐 실험에서 옥시토신을 투여하면 알코올에 의한 협응 장애가 사라져 음주 상태가 ‘보이지 않게’ 된다[10][11][12].
이러한 옥시토신-알코올 상호작용은 인간의 사회적 위험 감수 증가와도 기전이 일치한다는 메타분석 결과가 보고됐다[2].
2. 내집단 애착이 공정성 판단 회로를 억제하는 근거
행동 지표
Ultimatum Game·자원배분 과제에서 참가자는 동일한 불공정 제안을 받을 때 타인보다 가족·친구·동료 제안을 20–40% 더 자주 수락했다[9][8][7].
뇌영상 지표
fMRI 연구: 축구 팬을 대상으로 한 실험에서, 자기 팀(내집단) 제안 시 전전두피질·전측섬엽의 불공정-민감 반응이 현저히 감소했다[6].
ERP 연구: 내집단 아동에게 자원을 배분할 때 불공정 조건에서도 P300(공정성 평가 지표) 진폭이 낮아져 신경학적 공정성 처리 자체가 줄었다[7].
다중 그룹 fMRI: 낯선 집단과 달리 가족·친구 조건에서는 전측섬엽 불쾌감 신호가 억제돼 불공정 제안을 용인하는 경향이 강해졌다[5].
3. 매개 기제: 옥시토신 → 내집단 편애 → 공정성 억제
옥시토신은 인-아웃그룹 구분 상황에서 내집단 호혜성은 강화하고, 타집단 공감·공정성은 저하시킨다는 일련의 이중맹검 연구들이 입증했다[13][14][15]. 이는 앞서 언급한 전전두피질·섬엽 억제와 직접 연결되며, 결과적으로 가족·내집단에 대한 ‘편파적 관대함’이 나타난다.
4. 한계와 향후 과제
대부분의 이미징 연구는 실험실 과제를 사용해 실제 가족 관계와 동일한 정서 강도를 완전히 재현하지 못했다.
옥시토신 효과는 개인 성격·문화 맥락에 따라 달라질 수 있어, 한국 가족 중심 문화에서의 강도는 추가 조사가 필요하다.
공정성 판단 부위 억제를 인과적으로 증명하려면 TMS·약리 차단 연구 등 추가 실험이 요구된다.
5. 결론
신경과학적 증거는
“강한 가족 유대 ⇢ 옥시토신 분비 ⇢ 전전두피질‧섬엽 억제 ⇢ 공정성 판단 약화”라는 연쇄 경로를 지지하며,
이는 일시적 알코올 취기와 신경-행동적으로 상당 부분 겹친다. 하지만, 문화‧개인차·실시간 호르몬 측정 등 후속 연구로 세부 기전을 더 확정할 필요가 있다.
결론:
팔은 안으로 굽는다.
참고문헌
[1] The dark side of the ‘love hormone:’ Similarities with … https://www.sciencedaily.com/releases/2015/05/150519210251.htm
[2] ‘Drunk In Love’ Now Backed By Science, As Alcohol And … https://www.medicaldaily.com/drunk-love-now-backed-science-alcohol-and-oxytocin-show-similar-brain-effects-334092
[3] Alcohol And Love Have Very Similar Effects On The Brain https://www.iflscience.com/hugs-not-drugs-alcohol-and-love-have-very-similar-effects-brain-31316
[4] Why falling in love is similar to being drunk https://www.telegraph.co.uk/news/science/science-news/11615997/Why-falling-in-love-is-similar-to-being-drunk.html
[5] Ingroup/outgroup membership modulates fairness … https://www.nature.com/articles/srep39827
[6] Not on my team: Medial prefrontal cortex responses to … https://onlinelibrary.wiley.com/doi/10.1002/brb3.1030
[7] Racial Ingroup Bias and Efficiency Consideration Influence … https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2021.630811/pdf
[8] Effects of Ingroup Identification on Ingroup Favouritism … https://pmc.ncbi.nlm.nih.gov/articles/PMC9687485/
[9] Ingroup favoritism overrides fairness when resources are … https://www.nature.com/articles/s41598–022–08460–1
[10] Sobering effect of the love hormone https://www.sciencedaily.com/releases/2015/02/150223164442.htm
[11] Oxytocin, The Love Hormone, Has A Sobering Effect On … https://www.medicaldaily.com/oxytocin-love-hormone-has-sobering-effect-drunk-rats-323474
[12] Rats can’t get drunk after a dose of oxytocin hormone https://www.newscientist.com/article/dn27016-rats-cant-get-drunk-after-a-dose-of-oxytocin-hormone/
[13] Oxytocin promotes human ethnocentrism https://www.pnas.org/doi/10.1073/pnas.1015316108
[14] Effects of Oxytocin on Social Comparisons in Intergroup … https://pmc.ncbi.nlm.nih.gov/articles/PMC8466309/
[15] oxytocin decreases the adherence to fairness norms - PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC3385212/
[16] Family cohesion, shame-proneness, expressive … https://pmc.ncbi.nlm.nih.gov/articles/PMC9382198/
[17] The Neuroscience of Fairness and Trust https://knowingneurons.com/the-neuroscience-of-fairness-and-trust/
[18] Why and how do founding entrepreneurs bond with their … https://www.sciencedirect.com/science/article/pii/S0883902617302987
[19] Oxytocin receptor gene and racial ingroup bias in empathy- … https://www.sciencedirect.com/science/article/abs/pii/S1053811915000592
[20] Neurocognitive Basis of Racial Ingroup Bias in Empathy https://www.sciencedirect.com/science/article/abs/pii/S1364661318300494
[21] Brain responses to self- and other- unfairness under … https://www.sciencedirect.com/science/article/pii/S105381192400199X
[22] In-group bias https://thedecisionlab.com/biases/in-group-bias
[23] Social distance and anonymity modulate fairness … https://www.nature.com/articles/srep13452
[24] Relationship between Salivary Oxytocin Levels and … https://www.nature.com/articles/srep38662
[25] Lost Connections: Oxytocin and the neural, physiological … https://pmc.ncbi.nlm.nih.gov/articles/PMC6037618/
[26] The oxytocinergic system and racial ingroup bias in … https://www.sciencedirect.com/science/article/abs/pii/S0028390824003204
[27] An association between biased impression updating and … https://www.sciencedirect.com/science/article/abs/pii/S0022103119304093
[28] SCARF: a brain-based model for collaborating with and … https://schoolguide.casel.org/uploads/sites/2/2018/12/SCARF-NeuroleadershipArticle.pdf
[29] Preferences and beliefs in ingroup favoritism - PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC4327620/
[30] What Happens in Your Brain When You Fall in Love? A … https://blissfulties.com/what-happens-in-your-brain-when-you-fall-in-love/
[31] Parent-Child Synchrony Isn’t Always Better for Attachment … https://neurosciencenews.com/parent-child-synchrony-attachment-25893/
[32] The neural correlates of group and personal rejection - PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC12130114/
[33] Change in brain asymmetry reflects level of acute alcohol … https://pmc.ncbi.nlm.nih.gov/articles/PMC10290692/
[34] Mind Mingle: Brain Synchrony in Family Dynamics https://scitechdaily.com/mind-mingle-brain-synchrony-in-family-dynamics/
[35] Neural basis of in-group bias and prejudices: A systematic … https://www.sciencedirect.com/science/article/pii/S0149763421004693
[36] Differential Sensitivity of Prefrontal Cortex and Hippocampus … https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0106945
[37] Why parents shouldn’t always be ‘in sync’ with their children https://www.bbc.com/future/article/20240524-why-neural-synchrony-between-parents-and-children-isnt-always-ideal
[38] Alpha-band synchronization to same-race pain but … https://www.sciencedirect.com/science/article/pii/S1053811920308855
[39] Disruption of Frontal Lobe Neural Synchrony During … https://pubmed.ncbi.nlm.nih.gov/30799848/
[40] Neurodiversity and Attachment https://www.attachmentproject.com/psychology/neurodiversity/
[41] Insights From fMRI Studies Into Ingroup Bias https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2018.01868/full
[42] Love and Brain | Psyche https://vocal.media/psyche/love-and-brain
[43] Neural representation of the parent–child attachment from … https://pmc.ncbi.nlm.nih.gov/articles/PMC9250301/
[44] Neurocognitive Basis of Racial Ingroup Bias in Empathy http://psy.pku.edu.cn/docs/20181226142849692633.pdf
[45] There Is a Fine Line between Love and Drunk https://www.scientificamerican.com/article/there-is-a-fine-line-between-love-and-drunk/
[46] Understanding social attachment as a window into the … https://pmc.ncbi.nlm.nih.gov/articles/PMC10585278/
[47] Neural correlates of face familiarity in institutionalised children … https://acamh.onlinelibrary.wiley.com/doi/10.1111/jcpp.13728
[48] The neural correlates of attachment security in typically … https://www.sciencedirect.com/science/article/abs/pii/S0278262617304463
[49] Lesion evidence for a causal role of the insula in aversion … https://pmc.ncbi.nlm.nih.gov/articles/PMC8881633/
[50] Medial prefrontal cortex reacts to unfairness if this … https://pmc.ncbi.nlm.nih.gov/articles/PMC4526475/
[51] Insights From fMRI Studies Into Ingroup Bias - PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC6174241/
[52] “An Eye for an Eye”? Neural Correlates of Retribution and … https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0073519
[53] Neural mechanisms of the mood effects on third‐party … https://pmc.ncbi.nlm.nih.gov/articles/PMC9294295/
[54] A review of neuroimaging studies of race-related prejudice https://pmc.ncbi.nlm.nih.gov/articles/PMC3973920/
[55] Effect of Modulating DLPFC Activity on Antisocial and … https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2020.579792/full
[56] Neural representations of Groups and Stereotypes using … https://www.nature.com/articles/s41598–019–39859-y
[57] The Critical Role of the Right Dorsal and Ventral Anterior … https://pmc.ncbi.nlm.nih.gov/articles/PMC7243851/
[58] The residential stability mindset increases racial in-group … https://www.sciencedirect.com/science/article/abs/pii/S0301051121001873
[59] Gender Differences in Behavioral and Neural Responses … https://www.nature.com/articles/s41598–017–13790–6
[60] Structural Differences in Insular Cortex Reflect Vicarious … https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0167538
[61] Anterior insula signals inequalities in a modified Ultimatum … https://pubmed.ncbi.nlm.nih.gov/28223239/
[62] A dual-fMRI investigation of the iterated Ultimatum Game … https://www.nature.com/articles/s41598–018–29233–9
[63] Lesion evidence for a causal role of the insula in aversion to … https://academic.oup.com/scan/article/17/3/266/6342863
[64] Framing the ultimatum game: the contribution of simulation https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2013.00337/full
[65] Baseline activation in anterior insula predicts inter … https://www.sciencedirect.com/science/article/abs/pii/S0301051113001506
[66] Agreement in the ultimatum game https://www.sciencedirect.com/science/article/abs/pii/S0732118X18300047
[67] Ventral Caudate and Anterior Insula Recruitment During … https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2020.00678/full
[68] Not fair but acceptable… for us! Group membership … https://www.sciencedirect.com/science/article/abs/pii/S0022103117300732
[69] Could research into oxytocin and alcohol lead to a ’sobriety … https://theconversation.com/could-research-into-oxytocin-and-alcohol-lead-to-a-sobriety-pill-37855
[70] Alcoholism and Oxytocin https://www.castlecraig.co.uk/alcohol-addiction/oxytocin/
[71] 6 interesting effects of oxytocin https://www.livescience.com/35219–11-effects-of-oxytocin.html
[72] Being in love produces same effects as alcohol on the brain https://podcasts.ufhealth.org/being-in-love-produces-same-effects-as-alcohol-on-the-brain/
[73] A Tale of Love and Its Divergent https://readersmagnet.club/a-tale-of-love-and-its-divergent/
[74] Oxytocin Therapy For Alcohol Use Disorder https://www.therecoveryvillage.com/alcohol-abuse/oxytocin-treatment/
[75] There Is a Fine Line between Love and Drunk - Thrivikramji.comhttps://thrivikramji.com/uncategorized/there-is-a-fine-line-between-love-and-drunk/
[76] Love and the Brain https://hms.harvard.edu/news-events/publications-archive/brain/love-brain
[77] The dark side of the ‘love hormone’; research points to … https://www.birmingham.ac.uk/news-archive/2015/the-dark-side-of-the-love-hormone-research-points-to-striking-similarities-with-the-effects-of-alcohol-1
[78] Attachment relationship and oxytocin among people … https://www.archivespp.pl/pdf-168686–97752?filename=Attachment+relationship.pdf
[79] Oxytocin, the ‘Love Hormone,’ Being Tested for Treatment … https://www.ucsf.edu/news/2017/04/406591/oxytocin-love-hormone-being-tested-treatment-ptsd-and-alcohol-abuse
[80] Oxytocin shows promise for alcohol and opioid addiction https://www.sydney.edu.au/news-opinion/news/2020/08/26/oxytocin-shows-promise-for-alcohol-and-opioid-addiction.html
