In the store model, STM and LTM are
distinct memory systems, whereas in the working memory view, “STM” is simply
the most active information in LTM.
Putative differences between coding, retrieval mechanisms, and
forgetting processes have lead proponents of the store model to treat STM and
LTM as separate systems; however, subsequent research has shown that such
differences may not in fact exist. For
example, it has been thought that information in LTM was semantically encoded
and information in STM was acoustically encoded. Yet, it was found that deaf subjects confuse visually similar
letter strings held in STM. This
finding suggests that information in STM is not exclusively acoustically
encoded.
It was also thought that displacement is a primary
source of forgetting in STM, while interference played a critical role in
LTM. However, it has been shown that
repeatedly asking subjects to store sets of categorically related items in STM
results in an apparent decrease in memory capacity: fewer words are recalled
accurately, and there are more intrusions from previous trials. This finding suggests that items from
previous trials are maintaining activation in LTM and inhibiting recall of
words on the current trial. In other
words, interference from active information in LTM can play a role in
forgetting in STM.
Findings such as these gave rise to the conclusion
that LTM and STM do not function as distinct systems. As an alternative to this view, the notion of working memory was
proposed. Working memory can be seen as
an aggregate of several components which function in concert, including a
central executive component, which allocates WM resources to slave systems such
as the phonological loop and the visuo-spatial sketchpad.
In sum, WM differs from STM in terms of its
hypothesized components, and also in terms of its relation to LTM. The components of WM are treated by some
researchers essentially as temporarily highly active forms of information in
LTM.