When the response does not match the threat: The relationship between threat assessment and behavioural response in ambiguous lethal force decision-making

Deciding when to use lethal force inherently depends on assessing threat, a process that itself incorporates numerous perceptual factors. This study assessed this relationship between perception-based threat assessment and behaviour-based threat response. Specifically, participants completed multiple tasks designed to elicit either a threat rating (e.g., perception-informed threat assessment) or a binary behavioural response (e.g., shoot/don’t-shoot). Actor posture and weapon presence significantly affected the threat assessment, which was an extremely powerful omnibus predictor of threat response. However, for ambiguous threat stimuli, perceived threat became a poor predictor for threat response relative to the omnibus test. Participants appeared to adopt additional rules to inform behaviour independent of the threat assessment when faced with an ambiguous situation. These results demonstrate an intriguing disparity between subjective threat assessment and the behavioural response to use force that does not apply well to ambiguous cases or adequately explain errors in lethal force decisions.