For over a century, stability of environmental context across related episodes has been considered a source of memory interference. However, contemporary memory integration theory generates a diametrically opposite prediction. Here, we aimed to resolve this discrepancy by manipulating local context similarity across temporally disparate but related episodes, and testing the direction and underlying mechanisms of memory change. A series of experiments show that contextual stability produces memory integration and marked reciprocal strengthening, whereas variable context results in one memory to dominate at a related memory’s expense. Intriguingly, however, retrieval patterns reversed when the original encoding contexts were reintroduced during memory recall. These observations (i) identify environmental context during new learning and subsequent recall as opposing determinants in the volatility of memory, (ii) present a challenge to several classic and modern theories on episodic memory change, and (iii) reconcile paradoxical predictions of memory interference and integration.
Episodic memory enhancement versus impairment is determined by contextual similarity across events
