Observing Interoceptive Threat: Gaze and Pupillary Responses Reveal Observational Fear Learning of Aversive Bodily Symptoms in Others

Individuals can learn to fear, not only through direct aversive experiences but also by observing others’ reactions to such experiences. The present study aimed to investigate observers’ gaze patterns and pupillary responses while watching another individual’s fearful reaction to an interoceptive threat, as well as observers’ subsequent expression of learned fear in the absence of direct threat exposure. Thirty-two participants underwent an Observational Learning Phase (OLP), during which they watched a demonstrator experience labored breathing, signs of distress, and fearful facial expression (observational US) paired with one conditioned stimulus (observational CS+), while the other stimulus (observational CS–) was never paired with the US (i.e., the demonstrator breathes normally as no dyspnea was induced, has a calm demeanor and neutral facial expression). In the subsequent Direct Expression Phase (DEP), observers were presented with the same CSs in the absence of the demonstrator and interoceptive threat (US). Within trials, pupillary responses diverged between CS+ and CS– across time bins, beginning shortly after observational CS onset. Across trials, CS-specific differentiation was most pronounced toward the end of the OLP reflecting learning over time. Following the observational US, observers’ dwell times were longer on the demonstrator’s face, but not the body, during CS+ compared with CS– trials. During the DEP, observers showed larger temporal changes in pupil responses, higher US expectancy, and greater self-reported fear toward the CS+ than the CS–, despite never having directly experienced the aversive bodily symptoms. These findings suggest that fear of interoceptive threat can be acquired through observation, with pupil dilation reflecting conditioned responses and gaze behavior indicating attention to socially relevant threat cues. This study advances our understanding of observational fear learning and highlights the role of visual attention in fear learning about interoceptive threats through mere observation. • Pupil responses differentiated threat (CS+) from safety (CS–) cues. • Self-reported fear and US expectancy confirmed successful observational learning. • Observers fixated longer at the demonstrator’s face during observed threat.