In search of the M-Gram: The structure of organization in free recall

This paper reviews three major classes of structural models of episodic and semantic memory which have been proposed to describe the organization of permanent memory. Although semantic memory workers have developed methods for obtaining representations of these models from empirical data, students of episodic memory generally have not. A method is presented for extracting representations of memory structure using output order information from a free recall learning task. It is shown that this method can be embedded within each of the three general models of memory structure to produce graphic representations of those structures. These representations may be obtained for individuals or for group data, and in some cases the nature and extent of individual differences in organizational structure can be characterized. A final section of the paper demonstrates the validity of the method using both real and simulated data, shows that the method is sensitive even to small differences in organizational structure, and illustrates the utility of this approach with an analysis of part-whole transfer. Within theories of memory, two broad classes of components can be distinguished. Structural components relate to the format, arrangement, and interrelationships among item traces in the memory system. Functional components relate to the processes by which items become encoded, are stored, and subsequently are retrieved. In the language of information retrieval, structural components of memory models describe or represent the data base of the memory system, while functional components describe the routines which operate upon this data base. Over the last two decades, the notion that the memory data base constitutes a highly organized system has played an increasingly dominant role in theory and research in human memory, particularly in the context of The author is profoundly grateful to Peter A. Omstein for his advice, guidance, and interest from the inception of this work through the writing of this paper. The author thanks Martha Friendly for assistance in data collection and editing, Peter Dean and Doug Vipond for thoughtful comments on the manuscript, and Susan Goldberg for cheerfully typing numerous revisions.