The working memory model by Baddeley and Hitch in 1974 is an alternative to the multi- store model, which was limited in its description of the STM.
It consists of three main components, the first one being the central executive, which has overall control. The central executive is directs attention to two slave systems, the phonological loop and the visual-spatial sketchpad.
The central executive has limited capacity but is able to process information from all the sensory systems, e.g. vision, hearing, etc. It controls attention and is used in problem solving/decision- making.
Visuo-spatial sketch pad stores and manipulates visual information. Visual information is what things look like and spatial information is the relationship between the two. Its input is from eyes or the LTM.
The phonological loop consists of two sub- systems; the phonological store, “the inner ear”, which allows acoustically coded information to be stored for a brief period of time (about two seconds), and the articulatory control system, “the inner voice”, which helps maintain information by sub-vocal information. The phonological loop also has a limited capacity.
In 2000, Baddeley introduced a new component to the WMM: the episodic buffer. Its purpose is to organize the information received from the other components with information about time and order.
[+]Cohen et al- higher brain activity in part of the brain known as the prefrontal cortex during a task where the central executive was working. This supports WMM as it proves the existence of central executive through biological evidence.
[+]Farah et al- patient LH and found that he was capable of visual tasks but was not capable of spatial tasks. This supports the WMM as it suggests that the VSSP consists of two stores, something that is also argued by the WMM.
[-] Baddeley (2001) added the episodic buffer making the model more complex.