Memory’s Penumbra: Episodic Memory Decisions Induce Lingering Mnemonic Biases

New for Old? When confronted with a visual stimulus, such as an object or a scene, the brain decides whether it is new, and thus deserves to be encoded as a new memory, or old, which triggers the retrieval of the previously encoded memory. When shown a series of stimuli, some of which are similar to, but not identical to, old memories, it becomes necessary to switch back and forth between encoding and retrieval processing. Using behavioral tasks performed by human test subjects, Duncan et al. (p. 485 ) took advantage of the fact that switching takes a second or two and found that a subsequent object, presented before switching has occurred, was more likely to be identified as new when the previous object was new, and identified as old when the previous object was old.