Event segmentation protects emotional memories from competing experiences encoded close in time

Fear memories are characterized by their permanence and a fierce resistance to unlearning by new experiences. We considered whether this durability involves a process of memory segmentation that separates competing experiences. To address this question, we used an emotional-learning task designed to measure recognition memory for category exemplars encoded during competing experiences of fear conditioning and extinction. Here, we show that people recognized more fear-conditioned exemplars encoded during conditioning than conceptually related exemplars encoded immediately after a perceptual event boundary that separates conditioning from extinction. Selective episodic memory depended on a period of consolidation, an explicit break between competing experiences, and was unrelated to within-session arousal or the explicit realization of a transition from conditioning to extinction. Collectively, these findings suggest that event boundaries guide selective consolidation to prioritize emotional information in memory—at the expense of related but conflicting information experienced shortly thereafter. We put forward a model whereby event boundaries bifurcate related memory traces for incompatible experiences. This is in contrast to a mechanism that integrates related experiences for adaptive generalization1–3, and reveals a potentially distinct organization by which competing memories are adaptively segmented to select and protect nascent fear memories from immediate sources of interference. Short breaks in a stimulus stream are sufficient to create event boundaries during fear conditioning, which modulate the recognition rate for in-episode stimuli.