Beyond Retrieval Competition: Asymmetric Effects of Retroactive and Proactive Interference in Associative Memory

Interference between similar associations poses a core challenge for episodic memory. While retrieval-based accounts have dominated past theories, it remains unclear whether retroactive interference (RI) and proactive interference (PI) can emerge independently of retrieval competition. To address this, we employed a two-alternative forced-choice (2AFC) associative recognition task that minimized retrieval competition by using same-list distractors. Participants studied overlapping (A–B, A–C) and non-overlapping (E–F, G–H) associations, followed by associative recognition and source memory judgments. Results revealed an asymmetric interference pattern: RI impaired recognition accuracy without affecting response times, suggesting degraded recollection due to representational suppression. In contrast, PI was reflected in longer response times without accuracy loss, consistent with increased retrieval demands stemming from encoding-related differentiation. Source judgments showed no integration-induced cost and even faster RTs for overlapping pairs, further supporting the operation of pattern separation during A–C encoding. These findings highlight the critical role of encoding—rather than retrieval alone—in shaping interference. RI and PI reflect distinct processes: suppression-driven weakening of prior traces versus complexity-induced retrieval delays, respectively. Our results challenge retrieval-centric models and underscore the need for encoding-focused frameworks in memory interference research. Future work should examine how encoding strength, contextual differentiation, and individual variability modulate interference effects across memory tasks.