Proceedings of the Annual Meeting of the Cognitive Science Society

Traumatic memory is marked by a paradox: after trauma exposure, individuals show overgeneralization of fear alongside vivid and over-specific sensory intrusions. Pattern Separation (PS), the orthogonalization of similar inputs into distinct memory traces, is typically considered protective against fear generalization, but its role in the formation of intrusions remains unclear. Here, we combined an Emotional Mnemonic Similarity Task (E-MST) with a Trauma Film Paradigm in healthy participants (n = 30-38 across analyses). Negative arousal significantly enhanced lure discrimination [F(1,32) = 39.66, p<.001, __p = .55], with the largest gains on visually distinct ("low-similarity") lures (d = 0.93). This effect was driven by suppression of gist responses and slowed reaction times, consistent with an adaptive vigilance mechanism. Critically, individual differences in negative-arousal precision for visually similar (hard to discriminate) lures predicted traumatic intrusion frequency, controlling for baseline neutral discrimination [partial r = .41, p = .026, 95% CI (.05, .68)]. Mnemonic flexibility, i.e., the magnitude of the negative-vs-neutral LDI shift, was associated with greater symptom recovery after extinction. These findings support a trade-off model in which negative arousal drives item-specific precision at the expense of contextual integration, generating potent yet decontextualized memory traces that subsequently lead to intrusions.