Neuroanatomical correlates of system-justifying ideologies: a pre-registered voxel-based morphometry study on right-wing authoritarianism and social dominance orientation

Abstract

System-justifying ideologies are a cluster of ideals that perpetuate a hierarchical social system despite being fraught with inequalities. Right-wing authoritarianism (RWA) and social dominance orientation (SDO) are two ideologies that have received much attention in the literature separately and together. Given that these ideologies are considered to be stable individual differences that are likely to have an evolutionary basis, there has yet to be any examination for volumetric brain structures associated with these variables. Here, we proposed an investigation of overlapping and non-overlapping brain regions associated with RWA and SDO in a sample recruited in Singapore. Indeed, it will be interesting to determine how RWA and SDO correlate in a country that proactively promotes institutionalized multi-culturalism such as Singapore. RWA and SDO scores were collected via self-report measures from healthy individuals (39 males and 43 females; age 25.89 ± 5.68 years). Consequently, voxel-based morphometry (VBM) whole brain and region of interest (ROI) analyses were employed to identify neuroanatomical correlates of these system-justifying ideologies. RWA and SDO scores were strongly correlated despite the low ideological contrast in Singapore's sociopolitical context. The whole brain analysis did not reveal any significant clusters associated with either RWA or SDO. The ROI analyses revealed clusters in the bilateral amygdala and ventromedial prefrontal cortex (vmPFC) that were associated with both RWA and SDO scores, whereas two clusters in the left anterior insula were negatively associated with only SDO scores. The study corroborates the claim of RWA and SDO as stable individual differences with identifiable neuroanatomical correlates, but our exploratory analysis suggests evidence that precludes any definitive conclusion based on the present evidence.

The neurobiology of political ideology: Theories, findings, and future directions

“…These authors successfully replicate Kanai et al's (2011) finding that amygdala volume predicts self-reported conservatism, but do not find relationships with insula, ACC, or PFC volume. Another recent pre-registered study conceptually replicates Kanai et al's (2011) findings in the political context of Singapore using the RWA and SDO scales (Balagtas et al, 2023). Given these results, we posit that amygdala volume is a robust neurobiological correlate of conservative ideology.…”

“…Some studies do find a link between insula volume and various measures of conservatism Lewis et al, 2012;Nam et al, 2018). However, other studies fail to corroborate this trend (Balagtas et al, 2023;Kim et al, 2020;Nash et al, 2017;Schumacher et al, 2023). Additionally, one study finds that conservatives exhibit greater insula activity in response to racially ambiguous faces (Krosch et al, 2021)-consistent with the heightened aversion toward non-normative appearances predicted by accounts that link conservatism to disgust sensitivity (Shook et al, 2018).…”

“…Existing research offers strong support for a link between amygdala structure and political ideology. Structural MRI studies assessing gray matter volume find that amygdala size predicts conservative identification (Kanai et al., 2011; Schumacher et al., 2023), RWA and SDO (Balagtas et al., 2023), and system justification (Nam et al., 2018). This latter finding lends support to the idea that heightened attention to uncertainty—mediated by amygdala functioning—encourages people to support existing social arrangements (Nam, 2020).…”

“…In structural MRI studies, insula volume predicts conservative identification (Kanai et al., 2011), system justification (Nam et al., 2018), lower SDO (Balagtas et al., 2023), and endorsement of purity (Lewis et al., 2012), a disgust‐related moral foundation that is highly correlated with social conservatism (Hatemi et al., 2019). However, other studies have failed to find a relationship between insula volume and ideology (Kim et al., 2020; Nash et al., 2017; Schumacher et al., 2023).…”

Exposure to Multicultural Context Affects Neural Response to Out-Group Faces: A Functional Magnetic Resonance Imaging Study

“…Another factor that modulates the in-group bias is people's beliefs. In particular, system-justifying theories consist of a set of ideals that legitimize and maintain a hierarchical social system, even when unequal, in order to preserve the status quo [34][35][36][37].…”