Two dissociable updating processes in working memory
He claimed that the information-processing capacity of young adults is around seven elements, which he called "chunks", regardless whether the elements are digits, letters, words, or other units.Later research revealed this number depends on the category of chunks used (e.g., span may be around seven for digits, six for letters, and five for words), and even on features of the chunks within a category.The central executive is responsible inter alia for directing attention to relevant information, suppressing irrelevant information and inappropriate actions, and coordinating cognitive processes when more than one task is simultaneously performed.A "central executive" is responsible for supervising the integration of information and for coordinating "slave systems" that are responsible for the short-term maintenance of information.
In general, memory span for verbal contents (digits, letters, words, etc.) depends on the phonological complexity of the content (i.e., the number of phonemes, the number of syllables), Several other factors affect a person's measured span, and therefore it is difficult to pin down the capacity of short-term or working memory to a number of chunks.
The other slave system, the visuospatial sketchpad, stores visual and spatial information.
It can be used, for example, for constructing and manipulating visual images and for representing mental maps.
Oberauer has extended Cowan's model by adding a third component, a more narrow focus of attention that holds only one chunk at a time.
The one-element focus is embedded in the four-element focus and serves to select a single chunk for processing.