Working memory’s limited capacity places significant constraints on people's ability to hold information while processing. However, skilled readers are able to effectively encode important information into long-term memory during comprehension. This chapter describes the long-term working memory theory (LT-WM), originally developed to explain how experts in various domains (including reading) enhance their working memory capacity by relying on rapid, skilled use of long-term memory. We first trace the development of the theory and the reasons it took the form it did in the mid-1990s. We explain that LT-WM was not viewed as a new form of memory, but rather as highly practiced use of long-term memory to rapidly and reliably link information together using meaningful associations, retrieval structures, and preexisting knowledge. Next, we describe how the theory accounted for many central phenomena in discourse comprehension. More recent work has proposed a form of LT-WM for syntactic processing as well, and we discuss current critiques of the original evidence advanced to support LT-WM. Finally, we describe recent studies on neural activity associated with LT-WM development in reasoning skills and language comprehension.

FIVE CENTRAL FEATURES OF THE THEORY

1. (1) We define working memory in terms of its function, namely maintaining efficient selective access to information that is needed to complete a given task. This function can be achieved in everyday skilled performance by a wide range of different mechanisms. In contrast, traditional short-term working memory employs only a small subset of those alternatives.

2. (2) The amount of information that can be maintained in accessible form in working memory for a specific task is not limited by a fixed capacity. As part of the extended skill acquisition necessary to attain very high levels of performance, experts acquire knowledge and skills to rapidly encode information in long-term memory such that the information can be efficiently accessed with retrieval cues (longterm working memory or LT-WM) whenever it is later needed to complete the task. Similar acquired mechanisms mediate the large working memory in skilled everyday performance.

3. (3) LT-WM is mediated by associative recall from long-term memory, and to function reliably it provides different types of mechanisms for overcoming the problems of interference resulting from repeated associations to related retrieval cues.

4. (4) LT-WM reflects a complex skill acquired to meet the particular demands of future accessibility for information with tasks within a particular domain of expertise. Domain-relevant skills, knowledge, and procedures for the task are so tightly integrated into the skills for encoding of information that the traditional assumption of a strict separation between memory, knowledge, and procedures is not valid for skilled performance.

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