Schematic memories develop quickly, but are not expressed unless necessary.

Episodic memory retrieval is increasingly influenced by schematic information as memories mature, but it is unclear whether this is due to the slow formation of schemas over time, or the slow forgetting of the episodes. To address this, we separately probed memory for newly learned schemas as well as their influence on episodic memory decisions. In this experiment, participants encoded images from two categories, with the location of images in each category drawn from a different spatial distribution. They could thus learn schemas of category locations by encoding specific episodes. We found that images that were more consistent with these distributions were more precisely retrieved, and this schematic influence increased over time. However, memory for the schema distribution, measured using generalization to novel images, also became less precise over time. This incongruity suggests that schemas form rapidly, but their influence on episodic retrieval is dictated by the need to bolster fading memory representations.