Recent evidence suggests that individual differences in intolerance of uncertainty (IU) are associated with disrupted threat extinction. However, it is unknown what maintains the learned threat association in high IU individuals: is it the experienced uncertainty during extinction or the combination of experienced uncertainty with potential threat during extinction? Here we addressed this question by running two independent experiments with uncertain auditory stimuli that varied in threat level (Experiment 1, aversive human scream (n = 30); Experiment 2, benign tone (n = 47) and mildly aversive tone (n = 49)). During the experiments, we recorded skin conductance responses and subjective ratings to the learned cues during acquisition and extinction. In experiment 1, high IU was associated with heightened skin conductance responding to the learned threat vs. safe cue during extinction. In experiment 2, high IU was associated only with larger skin conductance responding to the learned cues with threatening properties during extinction i.e. mildly aversive tone. These findings suggest that uncertainty in combination with threat, even when mild, disrupts extinction in high IU individuals. Such findings help us understand the link between IU and threat extinction, and its relevance to anxiety disorder pathology.

The devil is in the detail: The role of threat level and intolerance of uncertainty in extinction