The Central Executive

This is the interface between the two subsystems and long term memory. It is more similar to an attentional system than a memory store, as is allocates resources to the visuospatial sketchpad and the phonological loop. Baddeley (1996) suggested that the model of attentional control proposed by Norman and Shallice (1980; 1986) could provide a good model of the central executive. The functions of the central executive, as suggested by Baddeley are listed below

• Retrieval strategies,
• timesharing in dual-task performance
• selecting attention
• temporary activation of the long term memory
• suppression of habitual, automatic responses and actions

Impairments to the central executive occur in a syndrome called 'Dysexecutive syndrome' or 'frontal lobe syndrome'. These result in effects which seem as if there is no system to allocate processing resources. Individuals with the syndrome have disturbed attention and are easily distractable, making it difficult for them to learn new tasks.

Evidence for the central executive can be seen through a test involving the random generation of digits or letters:

• The participant is required to hold 1-8 digits in their memory while generating a random sequence of digits of letters.
• Close attention is needed to prevent the repetition of digits or the production of stereotyped responses (non random)
• The results show that as the digit memory load increases, the randomness decreases and the responses become more stereotyped.
• There is an implication that during the production of novel schema (made up random digits) the dominant schema (non-random sequences) must be constantly inhibited by the SAS .

Automatic Processing and Working Memory

Jansma, Ramsey, Slagter and Kahn (2001)

• Looked at fMRI and development of automatic processing in constistent mapping.
• Practice was associated with reduces usage of capacity-limited working memory. (central executive)
• Automatic processing was evidenced by decreased activation of the left dorsolateral prefrontal cortex and the right superior frontal cortex
• Automatic and controlled processing have similar functional anatomical representation but differ in efficiency of working memory processing.

Schneider and Shriffin (1977)

• They Proposed clear theoretical distinctions between controlled and automatic processing
• Controlled: limited capacity, requires attention, flexible (can be modified)
• Automatic: Unlimited capacity, no attention required, inflexible (cannot be modified)

Norman and Shallice (1986)

• Fully and partially automatic processes
• controlled by supervisory attentional system (similar to the central executive see working memory lectures)

Cognitive Bottleneck

• Pashler et al. (2001)
• Experiment requires rapid response to 2 stimuli
• the second is presented close in time to the first which results in a slowed response to the second.
• Physiological Refractory period: processing bottleneck: cannot select response to 2 stimuli at the same time, can only respond serially
• This suggests that fully automatic processing rarely occurs.