Sensory competition during working memory strengthens long-term memory

Working memory (WM) continually interacts with the external environment, yet how such interactions shape short- and long-term memory remains unclear. A key factor modulating this influence is the perceptual similarity between external inputs and WM content. Sensory inputs that resemble what we hold in mind could facilitate or interfere with WM content, or simultaneously engage both processes. To adjudicate between these possibilities, we developed a WM task using naturalistic stimuli in which a task- irrelevant distractor appeared during WM maintenance. We systematically varied the similarity of this sensory input to both task-relevant and -irrelevant WM items. To assess how competition between WM and sensory inputs shapes long-term memory (LTM), we later tested memory for stimuli encountered in the WM task. Across two studies, we found that moderate similarity between sensory inputs and behaviorally relevant WM content yielded the best WM performance, whereas dissimilar or highly similar inputs impaired it. These results suggest that perceptually similar inputs can support WM representations up to a point, beyond which interference dominates. Strikingly, stronger interference during WM predicted better long-term memory, indicating that competition between internal and external representations promotes durable encoding. Together, these findings reveal how perceptual overlap between thought and perception shapes both momentary cognition and lasting memory.