"Schema Abstraction" in a Multiple-Trace Memory Model

A simulation model of episodic memory, MINERVA 2, is applied to the learning of concepts, as represented by the schema-abstraction task. The model assumes that each experience produces a separate memory trace and that knowledge of abstract concepts is derived from the pool of episodic traces at the time of retrieval. A retrieval cue contacts all traces simultaneously, activating each according to its similarity to the cue, and the information retrieved from memory reflects the summed content of all activated traces responding in parallel. The MINERVA 2 model is able to retrieve an abstracted prototype of the category when cued with the category name and to retrieve and disambiguate a category name when cued with a category exemplar. The model successfully predicts basic findings from the schema-abstraction literature (e.g., differential forgetting of prototypes and old instances, typicality, and category size effects), including some that have been cited as evidence against exemplar theories of concepts. The model is compared to other classification models, and its implications regarding the abstraction problem are discussed. How is abstract knowledge related to specific experience? In present-day terms, this question concerns the relationship between episodic and generic memories. This article explores the possibility that there is only one memory system, which stores episodic traces, and that abstract knowledge as such does not have to be stored but can be derived from the pool of traces of specific experiences at the time of retrieval. I demonstrate how this might work by applying a simulation model of a multipletrace memory theory to the sehema-abstraction experimental paradigm, which is widely believed to capture in the laboratory the processes by which generic or abstract ideas are formed. Multiple-trace theories assume that each event to which one attends gives rise to its own memory trace. Thus, repetition of an item such as a word in a list does not strengthen a prior representation (i.e., one predating the experiment or one laid down by the item's first experimental occurrence); rather, it produces a new trace that coexists in memory with traces of other occurrences of the same item. Experiments supporting the multiple-trace assumption have been primarily concerned with the ability of subjects to remember an item's presentation frequency, list membership, presentation modality, exposure duration, serial position, and so forth (e.g., Hintzman, 1976; Hintzman & Block, 1971; Hintzman, Block, & Summers, 1973;