Differentiating a chunk from a group : the role of verbal rehearsal in creating a hierarchical list structure

Title from PDF of title page (University of Missouri--Columbia, viewed on October 31, 2012).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Nelson CowanIncludes bibliographical references.Vita.Ph. D. University of Missouri--Columbia 2012."July 2012"[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Working memory, the small amount of information that can be temporarily held in mind, can be boosted through the use of mnemonic processes. The purpose of the proposed research is to distinguish between two such processes, chunking and grouping, on the basis of how they interact with a third process, covert verbal rehearsal. Chunking refers to the combination of items based on learned associations (for example, associations between the letters within each of the three acronyms FBI, CIA, IRS). Grouping refers here to the use of external cues to perceive some items as belonging with others (based for example on the pause between the first three and last four digits of a telephone number). In the literature, chunking and grouping have often been confused and interchanged; some researchers have gone so far as to give them a common definition. The present research suggests that there is an important distinction between them, which can be observed especially when the opportunity for covert verbal rehearsal is manipulated. Covert verbal rehearsal appears separate from chunking, with both of them independently helping recall. In contrast, rehearsal interacts with grouping cues to determine the way in which the list is processed. Recall and its timing are discussed in terms of the mental organization of the list, which is influenced by chunking (strongly) or grouping (weakly), and the retention of serial order, which can be provided by either chunking or rehearsal but not by grouping alone.Includes bibliographical references