Acute threat enhances perceptual sensitivity without affecting the decision criterion.

Threatening situations ask for rapid and accurate perceptual decisions to optimize coping. Theoretical models have stated that psychophysiological states, such as bradycardia during threat-anticipatory freezing, may facilitate perception. However, it's unclear if this occurs via enhanced bottom-up sensory processing or by relying more on prior expectations. To test this, 52 (26 female) participants completed a visual target-detection paradigm under threat-of-shock (15% reinforcement rate) with a manipulation of prior expectations. Participants judged the presence of a backward-masked grating (target presence rate 50%) after systematically manipulating their decision criterion with a rare (20%) or frequent (80%) target presence rate procedure. Threat-of-shock induced stronger heart rate deceleration compared to safe, indicative of threat-anticipatory freezing. Importantly, threat-of-shock enhanced perceptual sensitivity but we did not find evidence of an altered influence of the effect of prior expectations on current decisions. Correct target detection (hits) was furthermore accompanied by an increase in the magnitude of this heart rate deceleration compared to a missed target. While this was independent of threat-of-shock manipulation, only under threat-of-shock this increase was accompanied by more hits and increased sensitivity. Together, these findings suggest that under acute threat participants may rely more on bottom-up sensory processing versus prior expectations in perceptual decision-making. Critically, bradycardia may underlie such enhanced perceptual sensitivity.