Miller (1956) asked participants to listen to strings of numbers or consonants of varying length and recall them in order. The average recall was 7+- 2 items (miller’s magical seven). Our STM is, therefore capable of holding between 5 and 9 items or chunks.
Baddeley and Hitch (1974) elaborated on the idea of STM. They proposed that it was not just for brief storage of information. They thought it was also actively processed the information and decided what to do with it-hence the term ‘working memory’. The working memory consists of three parts as shown in the diagram below.
The central executive decides how to share out the limited resources of STM. It decides what is and is not to be attended to. It is also ‘modality free’ which means that it deals with both auditory and visual stimuli. The central executive has limited capacity and deals with tasks that are cognitively demanding.
An articulatory loop deals with verbal in formation and is essentially a rehearsal system. It is likely that the capacity of this system is limited to that which can be read aloud in approximately two seconds (Baddeley et al 1975).
A visuo-spatial sketchpad that can hold, and rehearse visual and spatial information. Baddeley and Lieberman !1980) suggested that the visuo-spatial sketchpad relies more on spatial coding than visual coding.
The important difference between the two-process model and the working memory model appears to be in the role of verbal rehearsal. In line with research findings that have cast doubt over the importance of verbal rehearsal, its role in memory is reduced to the articulatory loop only.
The working memory model can explain how, in brain-damaged patients, selective deficits may occur in short-term memory. An updated version of the model has been propsed by Baddeley (1986). This sees the articulatory loop as comprsing a passive phonological store (voncerned with speech perception) and an articulatory control process (concerned with speech production). The revised model was better able to explain some of the neurophysiological evidence that did not fit the original model. Craik and Lockhart (1972) disagreed with Atkinson and Shiffrin’s idea that memory consited