Working Memory Model: Overview of Theoretical Approaches

In 1960s, researchers were inspired by the invention of computer system and characterised STM as a computer with limited capacity which most verbal information is temporarily stored (Broadbent, 1958). Atkinson and Shiffrin (1968) then introduced a Dual-Store Model that maintained the short-term memory’s capacity is limited and rehearsal for the retention of information is essential. However, Baddeley and Hitch (1974) disagreed with the idea that short-term memory was a unitary system and introduced a multi-component system, which was the three-component working memory model which comprises of two subsidiary systems, inclusive of phonological loop and visuospatial sketchpad, and the central executive. Generally, working memory is defined as a restricted capacity system which allows momentary storage and operation of information for multifaceted cognitive tasks (Baddeley and Hitch 1974). It aids in the understanding of memory process in cognitive tasks and is a platform for thinking processes that involve temporary memory storage. The original model consists of three components, central executive which controls attention and manipulate other processes, phonological loop that retains speech-based memory, and visuospatial sketchpad that holds visual and spatial information (Baddeley and Hitch, 1974).

Phonological loop and visuospatial sketchpad are subsystems that hold information passively while central executive is the main drive of the memory process (Baddeley and Hitch, 1974). However, the model did not describe on the effects of stored knowledge on the memory. Thus, a new component, episodic buffer, was added as an account of the relationship between long-term memory and working memory, integration of information from other components, and the additional storage capacity (Baddeley, 2000). Although Baddeley’s (2000) working memory model is known as most influential working memory models in modern psychology history, it might not be the most suitable modal in explaining humans working memory for three reasons, the validity of phonological loop, ambiguity of the memory capacity, the vagueness of episodic buffer and the compatibility of visuospatial sketchpad.

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This essay will briefly describe basic concepts of each components in Baddeley’s (2000) working memory model and evaluate the components by examining whether the functions of each component is comprehensive. Firstly, phonological loop which is said to be the most well-developed component is not comprehensive in describing the implications of its functions. It should first be understood that there are two main constituents of the loop, phonological store and articulatory control process (Baddeley, 2000). Phonological store holds verbal and acoustic information temporarily until the information decay, which takes about 2 seconds, while articulatory control process functions to translate visual information to speech-like codes and to counteract the decay process of information by refreshing traces in the phonological store (Baddeley, 2000). Thus, it could be said that the decay of the information could be prevented by rehearsing the items; Rehearsal is essential to prevent information from fading. However, recent research found that rehearsal and decay have an ambiguous trade-off (Nairne, 2002). It is proposed that working memory would decay when the items are not rehearsed, and this is due to the time-based word-length effect which shows that words with shorter time for pronunciation are easier to be recalled (Baddeley, Thomson, and Buchman, 1975). Yet, Lovatt, Avons and Masterson (2000, 2002) found out that there was a reverse word-length effect from the outcome of the replicated experiment as the percentage of recalling lengthier words was higher. It is seemed that only particular sets of words could produce a positive outcome for the experiment, and the inconsistency of the experiment outcomes obtained by researchers may show that the theory is not significant. Apart from that, episodic buffer as a relatively innovative element in the working memory model is subjected to the uncertain validity due to the lack of sound experimental research.

Suggesting that working model has a role in consciousness and binding information from different storage, visuospatial sketchpad and phonological loop, Baddeley (2000) postulated the possibility of a component, which is episodic buffer, would act as a medium synergising information across different component. It could act as the medium for integrating and binding information from different components (Baddeley, 2000). Despite it is said to be the connection between working memory and long-term memory, there is no clear explanation regarding how the subsystems work and coordinate simultaneously. This has led to a problem which is the inability to explain some findings such as the long-term memory’s effects on the immediate serial recall. Nobre et al. (2013) have also conducted systematic review on the past research from year 2000 to 2013 to examine the validity of the episodic buffer and have found out that some tasks fail to meet the experimental optimum conditions while some standardised tests lack of empirical evidence nor theoretical arguments in explaining the involvement of episodic buffer in the tasks. This clearly shows that the validity of episodic buffer remains a question. Notwithstanding it is being introduced as an integrating medium to all information from different components, it hardly explains the interactions between multiple component. In addition, Baddeley (2012) himself has also admitted that episodic buffer remains a debatable topic. Thus, the researcher should provide more insights on how it could help in explaining the interaction between all components. Furthermore, although visuospatial component is the often the least controversial, Logie (1995) argued that there is a need to further developed visuospatial sketchpad into specified separated components, such as colour, shape, objects and locations.

The current visuospatial sketchpad is said to be too simplistic in describing the complexities of how visual and spatial information being registered to one’s memory. The point is that visual and spatial information are not equivalent and thus probable have a separated system. To examine the visuo-spatial separation hypothesis, Sanada, Ikeda, and Hasegawa (2015) replicated Wood’s (2011) experiment, which the outcome showed that shape and spatial working memory capacities have commonly-shared limitations, and the researchers have obtained a similar outcome confirming that the storage system between shape and spatial working memory system is shared, yet it was also found out that the overlapping area is minimal. Hence, the separation of visual and spatial working memory hypothesis could be reasonable to allow a further expand on this area in the future. Other than that, the new working model does not address the limited capacity of the system. Working memory is said to be limited, and thus Nairne (2001) assessed the long-term memory span by replicating past experiments and the outcome has shown that participants are able to averagely recall 5 two-syllable words even when the researchers have added 5-minutes delay before participants were asked to recall the list they memorised. The 5 minutes delay is supposedly beyond the capacity of working memory. Had this is true, the average memory slots for one’s long-term memory capacity is merely five. Other than that, the experiment outcome might be influenced by the requirement of memorising items in a particular order, which imposes a limit on the memory capacity. It might not be suitable to assess the actual memory capacity. In conclusion, although it is true that Baddeley (2000) working memory model is influential in modern psychology field, it is not comprehensive in explaining the components, such as episodic buffer, phonological loop, visuospatial sketchpad, and the memory capacity precisely. Future research could be based on the working model to study the unexplained aspects of the working model to understand the model in-depth. Lastly, despite the controversies of the working memory model, the contribution of the working memory model in the field of study still needed to be acknowledged.