Intolerance of uncertainty modulates brain-to-brain synchrony during politically polarized perception

Abstract

Political partisans see the world through an ideologically biased lens. What drives political polarization? Although it has been posited that polarization arises because of an inability to tolerate uncertainty and a need to hold predictable beliefs about the world, evidence for this hypothesis remains elusive. We examined the relationship between uncertainty tolerance and political polarization using a combination of brain-to-brain synchrony and intersubject representational similarity analysis, which measured committed liberals' and conservatives' (n = 44) subjective interpretation of naturalistic political video material. Shared ideology between participants increased neural synchrony throughout the brain during a polarizing political debate filled with provocative language but not during a neutrally worded news clip on polarized topics or a nonpolitical documentary. During the political debate, neural synchrony in mentalizing and valuation networks was modulated by one's aversion to uncertainty: Uncertainty-intolerant individuals experienced greater brain-to-brain synchrony with politically like-minded peers and lower synchrony with political opponents-an effect observed for liberals and conservatives alike. Moreover, the greater the neural synchrony between committed partisans, the more likely that two individuals formed similar, polarized attitudes about the debate. These results suggest that uncertainty attitudes gate the shared neural processing of political narratives, thereby fueling polarized attitude formation about hot-button issues.

Keywords: brain-to-brain synchrony; intersubject representational similarity analysis; intolerance of uncertainty; political polarization.

Fig. 1.

(A) Participants underwent fMRI and behavioral testing as part of a larger study on political cognition. (B) Participants viewed three videos in a fixed order while undergoing fMRI. (C) Participants were clearly divided on political ideology. (D) Analytical approach. We tested for variation in neural synchrony as a function of ideology and IUS. The statistical map slice is taken from Fig. 2C.

Fig. 2.

(A–C) Ideology similarity drove the greatest brain-to-brain synchrony during an inflammatory political debate video (C). Statistical thresholds: voxel-wise P (FDR) < 0.05, cluster size ≥ 5 voxels (135 mm³). Slice numbers indicate MNI × coordinate. (D) Activity time courses in mOFC were synchronized between like-minded individuals. Representative pairs of subjects exhibiting neural synchrony in the mOFC are presented for the first 2 min of video 3, during which liberal Democrat Tim Kaine is speaking. BOLD is z-scored at the subject level; time courses are smoothed using a 6-s rolling window average to reveal trends at the intrinsic timescale of the BOLD response.

Fig. 3.

(A) Neural synchrony in key socioemotional brain regions was driven by the interaction between uncertainty intolerance (IUS) and ideology. Thresholds: voxel-wise P (FDR) < 0.05 and cluster size ≥ 5 voxels (135 mm³). (B) Simulating neural synchrony from the regression model (with unstandardized ideology similarity to illustrate the effect) revealed that joint IUS exacerbated neural polarization: The ideological similarity of a dyad (continuous) more strongly predicted neural synchrony when participants were intolerant to uncertainty (high in joint IUS). (C) Estimated marginal effects for neural synchrony by joint IUS (lower quartile, Q1, and upper quartile, Q3) confirmed this interpretation: High IUS boosted neural synchrony in participant pairs with similar ideology (high-ideology similarity) and lowered synchrony for ideologically opposed dyads (low-ideology similarity). Shaded zones represent 95% CIs. Regression coefficients are reported in SI Appendix, Table S3.