What is working memory? Definitions, operationalization and domain.

Abstract

Definitions Working memory (WM) is viewed as an " interface " between cognition and action [1] and has been defined in various ways. It has been described as the maintenance of task relevant information for easy access during a task (storage capacity only); as storage capacity+processing of that information [2], and as storage capacity+retrieval of information from " long-term " memory, if information-maintenance fails [3]. The former definition, storage capacity only, is the same as that used for short-term memory (STM), which is described as a theoretical short-term storage system [4]. In this case, the distinction between WM and STM is ignored. The WM model proposed by Baddely [4] has received relatively consistent empirical support [5]. According to this model, WM is a multicomponent entity with two independent subsystems and a central executive (CE). The two storage systems consist of the phonological loop (PH) and the visual-spatial (VS) sketchpad. The phonological loop maintains relevant verbal information and the visual-spatial sketchpad holds relevant visual-spatial information active during a task. The central executive is the control system that coordinates the two subsystems, interacts with long-term memory, directs attention to relevant information, and inhibits task-irrelevant information. A class of WM models is collectively referred to as " State-based " models. These models describe WM as the ability to direct attention to " internal representations " [6]. Accordingly, WM is the ability to select a given representation and maintain it by actively attending to it. In these models, limited capacity of WM is the result of attentional prioritization. One such model is the Embedded Processes Theory. In this model, Cowan describes WM as a limited capacity attentional system that focuses attention on activated regions in the LTM. Another extensive theoretical account of WM is provided by Engle and colleagues [2]. Their model includes inhibitory control as an important component of WM. The inhibitory component works by suppressing interference from irrelevant information and distractors.