ABSTRACT
Virtually all theories agreed that if verbal short-term memory was characterized by any single task, that task was digit span, with longer sequences of digits occupying more of the capacity of the underlying short-term storage system. Working memory is assumed to be directed by the central executive, an attentional controller rather than a memory system. Its main mode of operation is assumed to be that proposed by D. A. Norman and T. Shallice, who assumed two modes of control, one of which is automatic and based on existing habits whereas the other depends on an attentionally limited executive. A major function of the central executive is that of attentional focus, the capacity to direct attention to the task in hand. Another attentional capacity that is attributed to the central executive is that of dividing attention between two or more tasks.
