Baddeley and Hitch 1974 believed the STM did

Baddeley and Hitch (1974) believed the STM did not consist of one store (as suggested by the MSM), there were a number of reasons behind this belief. -If you attempt to perform two tasks at the same time which require the same resources (e. g. two visual tasks) you will perform both tasks less effectively than if you were to do them on their own (dual task) -If you attempt to perform two tasks at the same time that require different resources (e. g. one visual and one acoustic) you will be able to perform them both as well as if you had done them on their own. These two findings led them to suggest that there are separate stores for visual and acoustic information.

The central executive (CE) directs attention to specific tasks, it decides how the brains resources are allocated to tasks. The resources refer to the phonological loop, visuospatial sketchpad and the episodic buffer (also known as the slave systems. Information arrives from sensory input of LTM. The CE has a very limited capacity, it cannot attend to too many things at once and is not able to store information. The phonological loop (PL) deals with auditory information and preserves the order of informaiton. Baddeley (1986) divided this further into -The phonological store which holds the words you hear, like an inner ear. -An articulatory process which is used for words you hear, like an inner ear. Words are repeatred silently, like an inner voice. The PL has a limited capacity. The visuo-spatial sketchpad (VSS) is used for tasks which require spatial planning (e. g. if you were to plan to walk from your bedroom to the kitchen or count the number of doors on your car). Visual and/or spatial information is stored here temorarily. Logie (1955) divided the VSS into two components -A visual cache which stores informaiton about visual items -An inner scribe which deals with spatial relations which stores the arrangement of objects in the visual field. The VSS has a limited capacity. The episodic buffer was developed by Baddeley (2000) as the original WMM did not have a general store. The PL and VSS deal with specific types of information. There was nowhere to hold information which relates to both visual and acoustic. The episodic buffer integrates information from the CE, PL and VSS. It maintains a sense of time sequencing, storing information like an episode. Information is sent to the LTM via the episodic buffer. The episodic buffer has a limited capacity of about four chunks (Baddeley, 2012).

What is the. CE Dual task Hitch and Baddeley (1976) tested dual task using the following method. They gave participants two tasks. Task 1 ocupied the CE (e. g. participants were given a statement ‘B is followed by A’ and shown two letters ‘AB’ and had to sat whether it was true or false). Task 2 either involved the articulatory loop (e. g. participants repeated the word ‘the’) or involved the CE and the articulatory loop (saying random digits). Task 1 was impaired when Task 2 involved both the CE and the articulatory loop. This demonstrates the dual task performance effect and shows that the CE does actually exist. Brain scans Braver et al. (1997) measured brain activity during tasks which required the use of the CE. They found greater activity in an area known as the left prefrontal cortex when participants were using the CE. As the task became more difficult activation in this area also increased. Thus supporting the existnce of the CE. KF Shallice and Warrington (1970) studied a man known as KF, his short term forgetting was greater for auditory information than visual stimuli. His auditory problems were limited to verbal material such as letters and numbers but not meaningful sounds (such as the phone ringing). His brain damage appeared to have only affected his phonlogical loop. Supporting the existence of the PL and the subomponents. SC SC had good learning abilities but was not able to learn word pairs which were presented out aloud, this suggests damage to his phonological store, thus supporting the existance of those components. (Trojano and Grossi, 1995). LH LH was involved in a road accident, LH performed better on spatial tasks than those involving visual imagery. This provides support for a separate visual and spatial system (Farah et al. , 1988). There is a lack of clarity over what the CE actually is and what it does. Baddeley (2003) claimed the CE is the most important but least understood component of the WMM. It has also been suggested we may have more than one CE. Eslinger and Damasio (1985) studied EVR who has a tumor removed. He performed well on reasoning test, thus suggesting his CE was functioning and intact. However, he had poor decision making skills, he would spend hours deciding what to eat, suggesting he had defects to his CE. There have been brain scan studies which also suggest we may have more than one CE (add study). External validity There is an issue of external validity with generalising findings from brain damaged patients.