This study investigated how encoding strength and consolidation shape proactive interference (PI) in associative memory. Using a Modified Modified Free Recall (MMFR) paradigm, participants studied overlapping (A-B, A-C) and non-overlapping (E-F, G-H) pairs. The encoding strength of List 1 was manipulated (one vs. three study repetitions), while List 2 was held constant. Cued recall was tested immediately and after a 24-h delay. Results showed that increasing List 1’s encoding strength enhanced overall recall for both overlapping and non-overlapping pairs, indicating more effective learning, but did not alter the magnitude of PI. Instead, PI was strongly modulated by retention interval. At immediate test, robust PI emerged across conditions, reflecting cue-based retrieval competition. After a 24-h delay, PI was reduced or absent when List 1 was weakly encoded but persisted in attenuated form when List 1 was strongly encoded, suggesting differential consolidation trajectories for overlapping and non-overlapping associations. Co-retrieval analyses further revealed reliable associative dependency between B and C across all conditions, consistent with representational linkages that promote cooperative retrieval. These findings highlight the dual influence of cue overlap: at the representational level, overlapping pairs form integrated structures that foster co-retrieval, whereas at the retrieval-processing level, cue overload induces competition and PI. Taken together, the results indicate that although initial encoding strength enhances overall recall of List 2, the persistence of proactive interference is influenced by consolidation processes.

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.

This study examined how the relative encoding strength of pre-existing associations influences proactive interference (PI), and whether memory consolidation modulates this effect over time. Using a Modified Modified Free Recall (MMFR) paradigm, participants studied overlapping (A–B, A–C) and non-overlapping paired associates(E-F, G-H). The encoding strength of List 1 was manipulated (one vs. three study repetitions), while List 2 was held constant. Recall was tested immediately and after a 24-hour delay.Results showed that PI was strongest when both lists were studied once, consistent with maximal cue-based competition. When List 1 was studied three times, PI was attenuated, suggesting reduced retrieval ambiguity. After a 24-hour delay, PI was eliminated in the equal-strength condition but persisted slightly in the strong List 1 condition. Co-retrieval analyses revealed consistent associative dependency between B and C across all conditions, indicating robust integration between overlapping traces.These findings demonstrate that retrieval competition in PI is modulated by both encoding strength and consolidation. While stronger encoding can reduce immediate competition, it may also prolong interference. The results underscore a dual-process framework in which cue overlap leads to both interference and cooperative retrieval, depending on the balance between differentiation and integration mechanisms.

Although associative interference has traditionally been attributed to retrieval competition, emerging evidence suggests that interference may also arise from encoding-based representational processes. The present study examined whether retroactive interference (RI) and proactive interference (PI) can occur in the absence of explicit retrieval competition and whether they reflect distinct underlying mechanisms. Participants studied two lists of word–picture pairs in an AB/AC associative learning paradigm, followed by a non-competitive two-alternative forced-choice (2AFC) associative recognition test and a source memory task. Across both frequentist and Bayesian analyses, recognition accuracy revealed a significant RI effect—lower accuracy for earlier A-B pairs relative to non-overlapping controls—whereas PI manifested as longer reaction times (RTs) for later A-C pairs, despite comparable accuracy. Source judgments showed faster correct responses for overlapping than for non-overlapping pairs, suggesting that cue overlap facilitated more fluent retrieval rather than confusion. These findings indicate that interference can emerge independently of retrieval competition and that RI and PI are supported by dissociable mechanisms: RI reflects encoding-related reorganization that weakens earlier associations, whereas PI reflects increased retrieval effort following differentiation of overlapping traces. Together, the results support a process-interaction framework in which encoding-based reactivation and reorganization shape later retrieval dynamics, demonstrating that associative interference arises from the interplay between encoding and retrieval processes rather than retrieval competition alone.