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 ...