Research on collaborative memory has unveiled the counterintuitive yet robust phenomenon that collaboration impairs group recall. A candidate explanation for this collaborative inhibition effect is the disruption of people's idiosyncratic retrieval strategies during collaboration, and it is hypothesized that employing methods that improve one's organization protects against retrieval disruption. Here it is investigated how one's learning method during the study phase--defined as either repeatedly studying or repeatedly retrieving information--influences retrieval organization and what effects this has on collaborative recall and post-collaborative individual recall. Results show that repeated retrieval consistently eliminated collaborative inhibition. This enabled participants to gain the most from re-exposure to materials recalled by their partners that they themselves did not recall and led to improvements in their individual memory following collaboration. This repeated retrieval advantage stemmed from the preferential manner in which this learning method strengthened retrieval organization. Findings are also discussed that reveal a relationship between retrieval organization and the interaction observed between learning method and short versus long delay seen in the testing effect literature. Finally, results show that the elusive benefits of cross-cuing during collaboration may be best detected with a longer study-test delay. Together, these findings illuminate when and how collaboration can enhance memory.

Memory research has primarily focused on how individuals form and maintain memories across time. However, less is known about how groups of people working together can create and maintain shared memories of the past. Recent studies have focused on understanding the processes behind the formation of such shared memories, but none has investigated the structure of shared memory. This study investigated the circumstances under which collaboration would influence the likelihood that participants come to share both a similar content and a similar organization of the past by aligning their individual representations into a shared rendering. We tested how the frequency and the timing of collaboration affect participants' retrieval organization, and how this in turn influences the formation of shared memory and its persistence over time. Across numerous foundational and novel analyses, we observed that as the size of the collaborative inhibition effect-a counterintuitive finding that collaboration reduces group recall-increased, so did the amount of shared memory and the shared organization of memories. These findings reveal the interconnected relationship between collaborative inhibition, retrieval disruption, shared memory, and shared organization. Together, these relationships have intriguing implications for research across a wide variety of domains, including the formation of collective memory, beliefs and attitudes, parent-child narratives and the development of autobiographical memory, and the emergence of shared representations in educational settings.

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Recent research has demonstrated a relationship between retrieval organization and the efficacy of prior repeated retrieval on delayed tests. The present study asked why repeated study engenders higher recall at a short delay despite lower retrieval organization but produces a decline at a long delay, and why repeated retrieval engenders lower recall at a short delay despite higher retrieval organization but produces stable recall over time. This relationship was examined through the inclusion of two successive recall tests-one immediately after learning method and one a week later. Results replicated the interaction in recall between learning method and delay characterizing the testing effect and, critically, revealed the qualitative differences inherent in the retrieval organization of each method. Specifically, stable recall in repeated retrieval was accompanied by strong and sustained conceptual organization, whereas organization for repeated study was tenuous and weakened across tests. These differences quantitatively were assessed through the use of five targeted analyses: specifically, the examination of cumulative recall curves, the accumulation of organization across time (a curve akin to cumulative recall), item gains and losses across time, changes in the size of categories across time, and the fate of specific clusters of recalled items across time. These differences are discussed within the context of differential processes occurring during learning method.