Genetic and Neural Basis of Cultural Norm Acquisition Open Access

Lee, Daniel (Summer 2022)

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Cultural norm acquisition is a process through which individuals learn normative beliefs and values prevalent in their cultural environment. A developing body of literature has suggested that a set of genes may modulate the way the brain processes normative social feedback from others, thereby contributing to individual variations in cultural norm acquisition. Yet, the specific intermediate mechanisms that support such "social sensitivity" remain elusive. The primary aim of this dissertation project was to explore the genetic and neural substrates of the cultural norm acquisition process, with a specific focus on genetic variation in the oxytocin receptor gene (OXTR). 195 healthy adult participants (Neuroimaging arm N = 50, Behavioral arm N = 145) performed three cognitive tasks in an imaging genetics experiment. The first task measured participants' ability to detect subtle emotional cues that convey evaluative social feedback (i.e., facial micro-expressions). The second task measured their ability to discriminate the authenticity of social feedback (i.e., genuine vs. posed smiles). The third task measured participants' susceptibility toward conformity pressure imposed on the domain of moral values and virtues (i.e., moral conformity). Participants' behavioral and functional magnetic resonance imaging (fMRI) data were analyzed with respect to a single nucleotide polymorphism in OXTR rs53576 and multi-locus genetic profile scores (MPS) that reflected the level of OXTR expression in the brain. We found that OXTR rs53576 G homozygotes detected facial micro-expressions better than the A allele carriers. This genetic modulation was associated with increased activations in the brain areas implicated in attentional control. Furthermore, G homozygotes were more likely to erroneously judge posed social cues as genuine, which was linked with decreased activations in the brain areas involved with mentalizing. Lastly, participants with higher MPS showed greater moral conformity. This effect was mediated by decreased activations in the brain area implicated in conflict processing. Despite a need for further replication, these findings illuminate specific neuro-cognitive pathways through which OXTR may facilitate or hinder the cultural norm acquisition process across individuals. It also suggests the potential utility of MPS as a means to characterize and explain various high-level social phenotypes in humans.

Table of Contents

Chapter 1: Introduction 1

Anthropological perspectives on cultural norm acquisition 3

Psychological perspectives on cultural norm acquisition 9

Cultural norm acquisition in social neuroscience 17

Cultural norm acquisition in social genomics 29

The current research: bringing existing lines of research together 34

Chapter 2: A common oxytocin receptor gene (OXTR) polymorphism modulates neural responses to negative facial micro-expressions 50

Abstract 51

Introduction 53

Method 57

Results 67

Discussion 73

Summary and Conclusion 81

Supplementary Materials 91

Chapter 3: The neural basis of smile authenticity judgments and the possible modulatory role of the oxytocin receptor gene (OXTR) 101 

Abstract 102

Introduction 104

Method 109

Results 118

Discussion 124

Summary and Conclusion 134

Supplementary Materials 149

Chapter 4: Enhanced endogenous oxytocin signaling modulates neural responses to social misalignment and promotes conformity in humans: A multi-locus genetic profile approach 157

Abstract 158

Introduction 160

Method 166

Results 178

Discussion 185

Summary and Conclusion 192

Supplementary Materials 201

Chapter 5: Conclusion 211

Summary of Main Findings 212

Significance 221

Possible Improvements and Ideas for Future Studies 226

Bibliography 232

Figures and Tables


Table 2-1. Participants demographics and genotype composition 87

Table 2-2. Participants’ average behavioral task performance 88

Table 2-3. Whole-brain activations for the effects of the Expression Type and the OXTR genotype 89

Table 3-1. Demographics and genotype composition of the study sample 144

Table 3-2. Results of independent sample t-tests on personality and demographic traits between the OXTR genotype groups in the behavioral arm 145

Table 3-3. Results of independent sample t-tests on personality and demographic traits between the OXTR genotype groups in the neuroimaging arm 146

Table 3-4. Summary of the whole-brain activations associated with the successful identification of genuine, posed, and neutral smiles 147

Table 4-1. Study sample demographics and genotype composition 199

Table 4-2. The list of the seven OXTR SNPs used for constructing MPS 200

Table 5-1. The main predictions of Experiment 1 213

Table 5-2. Summary of the main findings of Experiment 1 214

Table 5-3. The main predictions of Experiment 2 216

Table 5-4. Summary of the main findings of Experiment 2 217

Table 5-5. The main predictions of Experiment 2 219

Table 5-6. Summary of the main findings of Experiment 3 220


Figure 2-1. The trial structure of the face emotion detection task 82

Figure 2-2. The average %Hit for the macro vs. micro-expressions by the OXTR rs53576 genotype 83

Figure 2-3. Brain activation for the macro- and micro expression vs. Neutral expression 84

Figure 2-4. The OXTR genotype modulated the BOLD responses within the SMG in response to negative macro-vs. micro-expressions 85

Figure 2-5. Genetic modulation of activation within the STS (a), AI (b), and IFG (c) for the contrast between the negative micro-expressions vs. macro-expressions 86

Figure 3-1. The schematic representation of the smile authenticity judgment task 137

Figure 3-2. The intergroup difference between decision bias (i.e., response criterion, C) (a), and the average %Correct for each smile category (b)138

Figure 3-3. Brain activations associated with correct identification of genuine or posed smiles vs. neutral expressions 139

Figure 3-4. Brain activations associated with correct identification of genuine vs. posed smiles (i.e., GenHit > PosHit) 140

Figure 3-5. Associations between signal detection parameters and activations in the IFG and dACC/mPFC 141

Figure 3-6. The results of ROI analyses showing significant genetic modulations of the activations in the TPJ and mPFC 142

Figure 3-7. Brain-behavior correlations found in the mPFC 143

Figure 4-1. Schematic representation of the card sorting task 195

Figure 4-2. The average normalized decision shift across the different social feedback conditions 196

Figure 4-3. Significant voxels identified from the contrast [Feedback-IC > Feedback C] 197

Figure 4-4. The genetic modulation within the pMFC lead to increased behavioral conformity 198

Supplementary Materials 

S2-1. Sample size determination and participant allocation strategy 91

S2-2. Personality traits of participants 93

S2-3. Stimuli Characteristics 95

S2-4. Zero order correlation between age and task performance 96

S2-5. Whole-brain activations for the effects of the Macro > Neutral and Micro > Neutral 97

S2-6. The results of ROI analyses 98

S2-7. The effect of the OXTR genotype on the perception of positive and negative micro-expressions 100

S3-1. Sample size determination and participant allocation strategy 149

S3-2. Pilot Experiment for Stimuli Selection 151

S3-3. Linear association between participants’ age and task performance in the behavioral condition 153

S3-4. The results of ROI analysis on the average activations for the contrast [SmilesAll vs. No Expression] and [GenHit vs. PosHit] 154

S3-5. The mOFC activation associated with the participants’ subject perception of smile authenticity 156

S4-1. Sample size determination and participant allocation strategy 201

S4-2. Descriptive statistics for demographic variables 202

S4-3. Test of regression of means (RTM) 203

S4-4. Exploratory analyses on the associations among personality traits, impression rating, and conformity 204

S4-5. Exploratory analyses on the association between OXTR and memory accuracy 205

S4-6. Activations in the Septal/Subgenual Area 206

S4-7. The results of the ROI analysis in the exploratory parametric modulation model 207

S4-8. The results of the exploratory whole-brain analysis 208

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