Working Memory and Attention

The working memory model was introduced by Baddeley and hitch in 1974. This model has been built on the findings of the dual study stating that there are four different components to our short term memory. This model is an alternative to the multi-store model of memory as it had proposed that short term memory is made up of more than one store. The components of the working memory model are the central executive which is controlled by environmental stimuli, the phonological loop which is an articulatory control system which stores information in verbal form, the visuospatial sketchpad which handles spatial or visual information. The last component which was added in 2000 is the episodic buffer which is a passive store of information. There has been extensive research supporting the working memory model despite this there has also been criticism regarding its function. I will thoroughly discuss the strengths and limitations of this model.

One of the major pieces of evidence supporting the working memory was understood by the dual task paradigm. The use of this dual -task technique studied processing by attention and executive functions. The dual-task paradigm requires the participants to simultaneously perform two tasks, the primary and secondary task. This technique exploits the theory that the cognitive system has a pool of cognitive resources. When the two tasks are performed simultaneously, the primary and secondary tasks share these cognitive resources that they require. Both the primary and secondary tasks performance is affected and decreased. This supports the idea that sound and vision are processed separately by memory.

Probes are a type of secondary task in which signals appear periodically during the experiment (Kerr,1973). participants are required to react as quickly as possible when the detect the probe. The dual-task performance is then compared to the performance in a single-task condition. The latency of the participant's reaction calculates the amount of cognitive resources that is used by the primary task. Although the findings of the dual-task experiment contributed to an increased understanding of cognition in humans there were many criticisms raised about the technique. Howe and Rabinowitz 1989 argued that the new interactions used for processing the primary and secondary tasks disabled any interpretation of performance in a dual-task situation.

During dual testing, the participants get confused by lists of items that sound similar but not by items with a similar meaning. This suggests that the phonological loop codes information acoustically and gets overloaded. Baddeley (2003) found that similar sounding letters (V, B, G, T) are not recalled as well as letters which do not sound similar. Another study which supports the working memory model is Nelson Cowan (2005), they suggest that working memory is more efficient if the information is chucked together. The experiments he conducted concluded that working memory handles 4 chunks of information best at a single time. The working memory model is also supported by brain scans indicating the functions of working memory which has been located in parts of the brain. The phonological loop is located in the temporal lobe while the central executive has been linked to the frontal lobes and the episodic buffer is in both hemispheres.

Another system in the working memory model is the visuospatial sketchpad, which is essential for the online retention of an object and spatial information. It has a limited capacity but is independent of the phonological loop. This can be proved as we are able to rehearse a set of digits while simultaneously making decisions about the spatial layout of the set of letters. Just like the other slave system, the phonological loop articulatory suppression interferes with maintaining verbal information. In the visual-spatial sketchpad , tracking a spot of light on a screen or random eye movements would decrease memory performance. Baddeley (1986) proposed that eye movements can act as a way of revisiting locations in memory just like an articulatory rehearsal. In addition, spatial interference tasks disrupt the rehearsal component and impair the performance of tests in spatial working memory but have no effect on nonspatial visual memory tasks(Cocchini et al,2002). Klauer and Zhao 2004 support Baddeley's understanding of the visuospatial sketchpad as they found that retention of visual shape or color information is interfered with by the visual perceptual input but not by a simultaneous demand in the spatial domain.

The central executive is the most important component of the working memory model. It is involved in decision making and problem-solving. It plays an important role in planning and merging information from the subsidiary systems for the short term and long term memory both. It's flexible as it can process information from any subsystem but it has a limited storage capacity so it can process a certain amount of information at a time.

Robbins (1996) had conducted an experiment on chess players and the role of the central executive in remembering the chess positions by investigating the effect of generating random letter strings. 20 chess players were given 10 seconds to remember the position of 16 pieces from a chess game. The participants either used the central executive by making random number sequences or used the articulatory suppression task. They found that the letter generation performed poorly and the articulatory suppression task had good recall. It concluded that the central executive plays a role in remembering the chess positions. This experiment was criticized and was claimed that the experiment design allows the researcher to claim cause and effect.

In neuropsychology, there has been a lot of evidence that disorders of executive control are associated with damage to the frontal lobes (Shallice,1982,1988). One feature of the central executive is its capacity to coordinate information from the two slave systems of working memory. A preliminary study indicated a deficit in episodic long term memory but also suggested an impairment across aspects in working memory both verbal and visuospatial (Baddeley, Bandera, Della, Sala,1988). They indicated that this impairment would reflect on the central executive so they set up tests on Alzheimer patients. They were tested on individual tasks reflecting the operation of the slave systems (visual, verbal) and were required to combine tasks. The results of this experiment support Baddeley's findings and are consistent with the hypothesis that the capacity to combine performance on two tasks is a necessary function of the central executive but it is impaired in patients with AD.

The episodic buffer was created 26 years after the original working memory model. Baddeley had added this third slave system in order to link together every piece of information from the other slave systems (visuospatial sketchpad, phonological loop) with information which relates to the order and time. The episodic buffer enables memories to be prepared for episodic long term memory storage. Baddeley 2000 called the episodic buffer the locus of binding functions. Repovs and Baddeley (2006) claimed that the features held by the episodic buffer are stored in single units as chunks. While Jarrold et al (2011) argued that the episodic buffer has more than one unit allowing binding together chunks of featured from different sources.

In conclusion, psychologists have tried to understand working memory and attention though models like Baddeley's working memory model through experimental research and neuropsychological case studies. The working memory model has been applied to real life tasks when performing dual task/interference experiments. There has been extensive research on this and the findings support Baddeley's working memory model and sub slave systems. If two tasks use the same component the tasks are performed less effectively but when the tasks use different components like the visual vers the auditory the task is performed better. Baddeley's findings on memory and attention is supported by neuropsychological research of case studies like KF. KF suffered brain damage and had difficulty accessing verbal information but the visual information was unaffected. This stipulates Baddeley's finding that there are different components for each of these functions. (Visual,hearing, etc). There had been an improvement of this model as the episodic buffer was added in 2000, this shows that this model is open to further research. On the contrary, very little is known about the central executive. Eysenck 1986 argues that the central executive may have more that one unitary system. The allocation and capacity has also been criticized by psychologist Richardson, 1984. This working memory model has its limitations as it only focuses on the short term memory so it can't be used as a comprehensive model of memory.

References

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