Emotion and list context modulate the impact of expectation on memory formation

Emotional events are often remembered more vividly than neutral ones, and unexpected events also tend to receive enriched encoding. However, little is known about how emotional valence and expectation violations jointly shape episodic memory. This study examined their combined influence by orthogonally manipulating emotional content and expectation during encoding. Participants first learned predictive contingencies in a rule-learning task. An encoding phase followed, in which some stimuli violated established expectations, while emotional content was manipulated orthogonally to expectation. Recognition memory was then tested for expected and unexpected stimuli. In mixed-valence lists (Experiment 1), unexpected stimuli enhanced recollection for negative and neutral items but not for positive ones. When arousal was matched across valence (Experiment 2), the benefit shifted to unexpected positive and neutral stimuli. In purely emotional lists (Experiment 3), the effect of expectation violations on recollection was diminished, and memory was shaped primarily by valence, with negative stimuli eliciting greater recollection than positive ones. These findings show that the mnemonic benefit of unexpected events is not uniform but varies with valence, arousal, and list composition. They support layered models of distinctiveness, suggesting that memory emerges from the interaction of item-level expectancy, emotional salience, and contextual variability.