Genetic and Neural Basis of Cultural Norm Acquisition Open Access
Lee, Daniel (Summer 2022)
Abstract
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
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
Figures
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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