Working Memory, Task Switching, and Executive Control in the Task Span Procedure.

Abstract

Four experiments explored the task span procedure: Subjects received lists of 1-10 task names to remember and then lists of 1-10 stimuli on which to perform the tasks. Task span is the number of tasks performed in order perfectly. Experiment 1 compared the task span with the traditional memory span in 6 practiced subjects and found little difference. Experiment 2 compared the task span and the memory span in 64 unpracticed subjects and also found little difference. Experiment 3 compared practice with consistent and varied lists to address retrieval from long-term memory. Experiment 4 manipulated the number of task switches and found that it had little effect on task spans. The results suggest there is no trade-off between storage and task switching, which supports some theories of executive control and challenges others.Executive control is the instrument of volition. It is the process by which the mind programs itself and exercises control over the execution of its programs. Executive control is an important topic in many areas of psychology, including cognitive science, cognitive neuroscience, life span development, psychopathology, and individual differences. Executive control appears in various guises, so it is studied in various ways. Two of the most popular domains in which it is studied are working memory and task switching. This article concerns the relation between working memory and task switching and what it reveals about the nature of executive control. It introduces a new experimental paradigm called the task span procedure that was designed to reveal the interaction between working memory and task switching: Subjects are given a list of tasks to perform and then a series of stimuli to perform them on. The task span procedure requires working memory to store the list of task names and keep track of progress through the list. It requires task switching because successive tasks on the list are generally different. It also requires subordinate processes, controlled by the executive, to perform the tasks on the list. The task span procedure addresses several issues that distinguish theories of working memory, including the nature of capacity limitations, the nature of information loss, and the role of long-term memory in working-memory spans. The task span procedure also addresses issues in the task-switching literature, including what is involved in changing from one task to another. The Task Span ProcedureIn principle, the task span procedure can involve any number of tasks of any kind. In everyday life, it could involve a series of chores you hope to accomplish on a weekend or a series of meetings in your office at work. In this article, the task span procedure involves three tasks that can be performed on numbers that are presented as digits (e.g., 3) or words (e.g., nine). The three tasks are magnitude judgments (i.e., is the number greater than or less than 5?), parity judgments (i.e., is the number odd or even?), and form judgments (i.e., is the number a digit or a word?). The task names specify ...

Voluntary Task Switching: Chasing the Elusive Homunculus.

“…Second, there may be common causes for the switch costs, but the explicit task cuing procedure may involve some extra process, such that it exaggerates switch costs. A number of researchers have shown that switch costs in the explicit task cuing procedure result from a cue encoding benefit as well as or instead of endogenous processes that change task set (Arrington & Logan, 2004b;Logan & Bundesen, 2003, 2004Mayr & Kliegl, 2003). This cue encoding benefit can be demonstrated with a modified version of the explicit task cuing procedure in which two cues are used for each task.…”

“…There has been a considerable amount of theoretical work aimed at understanding the cognitive processes involved in the explicit task cuing procedure (Arrington & Logan, 2004b;Logan & Bundesen, 2003, 2004Mayr & Kliegl, 2003;Schneider & Logan, in press). The modal interpretation is that switch costs represent top-down control processes engaged in reconfiguring the cognitive system to perform a new task.…”

“…First, the procedure must not provide complete environmental support so that top-down processing is necessary. The explicit task cuing procedure fails to meet this criterion because it provides complete environmental support, and the reduction in switch costs with preparation interval can be explained as a cue encoding benefit (Arrington & Logan, 2004b;Logan & Bundesen, 2003, 2004. Second, the reduction in switch costs must not be confounded with the time since the last task was performed.…”

The Construct of Attention in Schizophrenia

“…In addition to representing stimuli, working memory can store task rules (25), and these rules can be used to control the operation of attention (whether input selection or rule selection). For example, an individual might be asked to find a red apple in a fruit bowl and put it in the largest of three boxes, and this might be stored as two rules in working memory (e.g., "select a red apple" and "put the selected object in the large box."…”

The task rule congruency effect in task switching reflects activated long-term memory.

“…Their interrelationships have been studied by means of a variety of approaches. These include examinations of WM load effects on task-switching performance (Baddeley, Chincotta, & Adlam, 2001;Emerson & Miyake, 2003), comparing WM span for tasks with WM span of items (Logan, 2004), individual differences studies (e.g., Miyake et al, 2000), and cognitive theorizing (e.g., Logan & Gordon, 2001;Mayr & Kliegl, 2000;Sohn & Anderson, 2001). The present study suggests an as-of-yet unrecognized link between these two functions by focusing on a highly replicable but poorly understood phenomenon from the task-switching literature, the task rule congruency effect (TRCE).…”