Intolerance of uncertainty modulates amygdala habituation to emotional faces

People differ widely in how they perceive uncertain situations as stressful and threatening. Intolerance of uncertainty (IU) captures these individual differences while operating as a transdiagnostic and transsituational risk factor. In the present study, we investigated how individual differences in the sensitivity to uncertainty, rather than broader anxious traits, influence the temporal dynamics of amygdala habituation to emotional faces. Eighty-five human participants (18 males) completed an emotional face-matching task during functional magnetic resonance imaging (fMRI) scanning. The habituation slope - reflecting the rate at which amygdala activation decreased across repeated face blocks - covaried with individual IU levels. Participants with lower IU showed steeper habituation slopes, indicating a rapid decrease in amygdala responses, whereas those with higher IU exhibited attenuated slopes, reflecting sustained activation over time. This effect remained significant after controlling for general trait anxiety. Because emotional faces convey varying degrees of affective and social ambiguity, they are potent elicitors of vigilance in individuals' sensitivity to uncertainty. This observed relationship between IU and amygdala habituation suggests that reduced neural adaptation to emotional stimuli may represent a core mechanism linking uncertainty sensitivity to anxiety vulnerability.