Your guess is as good as mine: A registered report assessing physiological markers of fear and anxiety to the unknown in individuals with varying levels of intolerance of uncertainty.

Individuals who score high in Intolerance of Uncertainty (IU) have a tendency to find uncertainty and the unknown aversive. However, there is a dearth of literature on the extent to which the known vs. the unknown during threatening contexts induce fear and anxiety in individuals with high IU. In the following registered report we attempted to address this question by manipulating the known and unknown in the threat of predictable and unpredictable aversive events task. Throughout the task, we measured a variety of self-report (ratings of valence and arousal) and physiological indices (skin conductance, pupil dilation, orbicularis oculi, corrugator supercilii). We collected data from 93 participants. Higher IU, relative to lower IU was associated with: (1) less discriminatory orbicularis oculi activity between cue and interstimulus interval periods across conditions, and (2) larger corrugator supercilii activity to the known predictable shock condition and smaller corrugator supercilii activity to the known unpredictable shock condition, compared to the other conditions. These findings provide evidence that IU-related biases manifest differently depending on the physiological marker of fear and anxiety and the type of known-unknown threat i.e. orbicularis oculi activity was related to generalisation across conditions, whilse corrugator supercilii activity reflected distress/relief during conditions with known threat. Ultimately, this research will inform future models of IU in relation to anxiety and stress disorders.