Physiological signatures of threat: A systematic review of threat-related stimuli processing

Zsidó, András N. and Pál, Gergő and Gonçalves-Bradley, Daniela and Kiss, Botond László and Coelho, Carlos M. (2026) Physiological signatures of threat: A systematic review of threat-related stimuli processing. SOCIAL AND PERSONALITY COMPASS. (Submitted)

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Abstract

Threatening stimuli engage cascades of autonomic (e.g., cardiovascular, respiratory, and electrodermal) and skeletomotor (e.g., postural freezing, startle, facial expressions, and goal-directed actions) responses, yet empirical findings across experimental paradigms remain heterogeneous and difficult to reconcile. This systematic review aimed to synthesise physiological findings published between 2000 and 2025 and indexed in PubMed and Web of Science, relating to the processing of threat-related stimuli across different stimulus categories. We synthesised the results by stimulus and measurement type. Twenty-six experiments (across 20 studies) met the inclusion criteria and comprised samples of healthy participants. Eighteen experiments used inherently emotional stimuli (e.g., pictures) and eight used conditioned threat cues. In terms of measurement type, we identified studies that measured skin conductance responses (SCR), heart rate (HR), respiration, pupil diameter, electromyography (EMG), and vocal intensity. Across studies examining emotional stimuli, SCR increased in response to threat, whereas HR and respiration exhibited mixed patterns reflecting orienting-related deceleration and arousal-related acceleration. Pupil diameter and startle responses were sensitive to threat but were also influenced by factors such as awareness and task demands. Facial EMG and vocal intensity increased in response to threatening images. Conditioning studies revealed robust SCR effects, reliable pupil generalisation gradients, and startle potentiation under learned threat. HR responses predominantly showed deceleration, modulated by anxiety levels and contextual factors. Together, these findings demonstrate that certain physiological markers reliably indicate threat perception, whereas the reliability of others depends on contextual factors. This body of evidence emphasises the value of physiological measures as indicators of attention to threats and suggests their potential as biomarkers in clinical research.

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