The working memory model

• The Working memory model was proposed by Baddeley and Hitch in 1974.
• The Working model of memory only focuses on the STM.
• The Working model of memory is only concerned with the part of the brain that is active when we are temporarily storing and manipulating information.
• The Working Model of memory consists of 4 component: the central executive, phonological loop, visuo-spatial sketchpad and the episodic buffer.
• Central executive is the supervisory component that has overall control of working memory. It has a limited capacity and processes sensory information. It doesn't store information itself and controls switching between tasks (e.g. visual or verbal).
• The central executive decides what to pay attention to, allocates tasks to slave systems and monitors incoming data.
• Phonological loop is the slave system that focuses on auditory information and preserves the order in which info arrives. 
• The phonological loop is subdivided into the ‘inner ear’ deals with auditory info (what is heard) and the ‘articulatory loop' which keeps words that are heard in the working memory via maintenance rehearsal using the 'inner voice’ to repeat words in our head.
• The visuo-spatial sketchpad is the slave system that stores visual and/or spatial information.
• The visuo-spatial sketch pad is subdivided into the visual cache which stores visual data and the inner scribe which records the arrangement of objects in visual field (spatial information and movement).
• The visuo-spatial sketch pad has a limited capacity of 3-4 items according to Baddeley (2003).
• The episodic buffer is a temporary store of memory that integrates information from the CE, PL, VSS, and LTM into a single memory, while maintaining a sense of time sequencing. It links the STM and LTM together.
• Baddeley at al. (1975) investigated what is known as the word length effect, where participants recalled more short words in serial order than longer words. This is because there is a limited space for rehearsal in the articulatory process (around 2 seconds). Baddeley concluded that the capacity of the PL is set by the duration of words and not the number of words.
• Shallice and Warrington (1970) studied a patient known as KF, who provides evidence for the WMM. KF suffered damage to his phonological loop as he had difficulty with sounds due to a motorcycle accident, but his visuo-spatial sketchpad was left intact as he could recall verbal information presented visually. As other parts of his STM were intact, he was able to transfer information to his LTM. This supports the existence of separate stores within STM and challenges the unitary STM concept of the MSM.
• A weakness of the WMM is that the central executive (CE) is not well understood. Some psychologists believe that the the definition of the CE is too vague as it is simply described as ‘organises resources’ and ‘focuses attention’, but no detail is given about how it actually operates. Critics also feel that the idea of one central executive is wrong and that it is likely there are sub-components to the slave driver. This means that the WMM is lacking a comprehensive explanation of the central executive's role, reducing its explanatory power.
• A strength of the WMM is that there is supporting studies such as Dual-task performance by Baddeley and Hitch. Baddeley and Hitch provided strong experimental support that there was different components of STM as stated in the WMM. Participants struggled to perform the task of tracking a light while visualising the letter F, as both tasks required the attention of the visuo-spatial sketchpad. When participants were presented with both a visual and verbal task, they struggled less as the tasks required different slave systems. This supports the idea in the WMM that there are separate slave systems that process different sensory info.
• A limitation of the WMM is that evidence from case studies of patients with brain damage cannot be generalised to the public. This is because they have serious damage to their brain which is rare. This means that their memory functions differently to the general public. Also, brain injuries are traumatic, and this trauma may be what causes the memory to change or perform worse on tasks, not the actual brain injury. This limits the WMM explanation of STM for the wider population.