What makes a scent trigger a memory? A cognitive decomposition of odor-evoked retrieval.

A single scent can unlock vivid memories. This study investigates the factors that make some odors more evocative than others. We examined odor-evoked episodic memory in 106 participants who experienced odors embedded in distinct visuospatial contexts, and whose memory was tested 24-72 h later. The protocol empirically dissociates odor recognition ("I've already smelled this scent") and associative memory ("It evokes a memory") processes. Using machine learning with SHapley Additive exPlanations, we identified distinct predictors for each process. Recognition was driven by emotional strength, especially for unpleasant odors, and the richness of verbal descriptions. Associative memory followed a U-shaped relationship with familiarity and was strongly influenced by semantic distinctiveness-how uniquely each odor was described. Together, these findings reveal that odor memorability depends not only on its emotional salience but also on how specifically it is conceptualized and how familiar we are with it.