Another group of issues concerns episodic memory. Narratives are stored in memory one at a time as they are read in, with only a single presentation. We do not usually have to go back and reactivate previous narratives after we have read a new story. However, the new story is recognized as an instance of a familiar sequence of events, and Attention is paid only to the facts that are specific to this story. It seems that episodic memory is structured to support classification based on similarities and storing the differences, and that this structure has been extracted from experience (Kolodner 1984).
Episodic memory structure also supports associative retrieval. A question supplies only partial information about the story it refers to, yet the story is retrieved with only the question as a cue. The more unique the story is in the memory, the less needs to be specified in the question. If there is only one travel story, we can unambiguously ask Where did John travel to? Usually, if there are several alternative stories, the most recent one is recalled by default. Context of the previous question can also be used to select among the alternatives (Lehnert 1978). And of course, it is possible to recognize a situation where there is nothing appropriate in the memory.