There is an argument that the phonological deficit theory does not satisfactorily explain all of the problems presented by dyslexia, such as poor organisation, concentration, distractibility (McLoughlin & Leather 2013:22), learning and automatisation difficulties (Nicolson & Fawcett 2010:137), physical co-ordination, eye movement control in reading and speech muscle control in speaking (Eide & Eide 2011:25).
The cerebellar theory (sometimes called the automaticity deficit) originates from Nicolson and Fawcett (2010) wherein they contend that an impairment of the cerebellum gives rise to difficulties in automatisation of skills, phonological and motor skills, articulation of speech and information processing speeds. It has been suggested by some that cerebellar deficits might be associative rather than causal (McLoughlin & Leather 2013:19).
Figure 2.2. Proposed causal chain for the cerebellum and reading, from Nicolson and Fawcett, (1999), adapted from Thomson (2009:127)
2.7.3 The role of working memory and the phonological and articulatory loop
Thomson states that the phonological loop is interesting to those studying dyslexia because of its relationship with language, reading, and speech (2009:172). Baddeley’s model of working memory (Baddeley 2007) is relevant to this study because of the demands of reading the words, making meaning, holding the information in the memory, processing it, responding, as in the acting of Shakespeare. In this review, I have thought it is necessary to include an account of the components’ mechanisms, so as to elucidate aspects of the model which emerge throughout my action research and the participants’ work during this study.
There is a widely-held opinion amongst researchers that many of those with dyslexia have poor working and short term memory, (especially verbal rather than visual), which might be a contributory factor in their inability to read
fluently (Gathercole & Packiam Alloway 2008:29, Mortimore 2008: 102, McLoughlin & Leather 2013:19). Working memory is said to be responsible for the temporary acquisition, storage and manipulation of information, and also acts as a ‘...translator between sensory input and long-term memory’, (Fletcher-Janzen, cited in Dehn 2008: xiii, Baddeley 2008:1).
Baddeley’s model has four components. These are: the central executive, the phonological loop, the visuospatial sketchpad and the episodic buffer.
Figure 2.3 Working memory and the phonological loop, (Baddeley, A. 2007:147)
i. The central executive
This is the focal point of working memory. It can focus on important information whilst blocking out disruptions, dual task by processing information and acting as a store, and has access to and from long term memory (Dehn 2008:22).
McLoughlin & Leather assert that, in their experience, those with dyslexia show problems with the function of the executive in aspects of planning,
Central Executive Visuospatial sketchpad Episodic Buffer Phonological Loop Visual Semantics Episodic Long Term Memory Language
sequences, attention and finding it hard to change a habitual manner of doing things, such as a ‘set’ reading style (2013:21).
The central executive supervises two ‘slave systems’: the phonological loop and the visuospatial sketchpad, which are interconnected by the episodic buffer.
ii. The phonological loop
The phonological loop is supported by the left part of the brain and ‘...plays a crucial role in language processing, literacy and learning’ (Baddeley 2008:17,
McLoughlin & Leather 2013:20). It has two departments. One is a short term
store for words, numbers or sentences. However, its capacity is limited. It can hold the information there for only a few seconds before it decays. This is known as short term memory. To ‘catch’ the information before it disappears; it has to be transferred into working memory, before it can be placed into long term memory. This ‘catching’ happens when the information seen is sub- vocalised, or vocalised: ‘either works equally well’ (Gathercole & Packiam Alloway 2008:87) in an articulatory rehearsal and transferred into a phonological code of phonemes or words. The phonological loop rehearsal can only hold a small amount of information at once, before it is forgotten. Monosyllabic words can be remembered more easily than polysyllabic words which take more time and effort in rehearsal articulation (Baddeley 2007:9). Ideas, reasoning and sense are then put together in the central executive area, which can then store them in long term memory.
It is common that those with dyslexia have problems with working memory overload and phonological processing which leads to inaccurate and slower language based learning (Eide & Eide 2011:24-25).
iii. The episodic buffer
As there is no direct pathway between the phonological loop and the visuospatial sketchpad, the episodic buffer acts a boundary between the two. It can act as a temporary storage space for the multi modal information from the two systems and long term memory and combine them into
representations to be stored in long term memory (Mortimore 2008: 107, Dehn 2008:25).
iv. The visuospatial sketchpad
The visuospatial sketchpad stores short-term visual images of things, places, and manipulation of space and plays a key role in creating images (Dehn 2008:19-22, Baddeley 2008:63-101). The visuospatial sketchpad is activated in the right side of the brain (McLoughlin & Leather 2013:22) and as yet there has been limited research into its full role and capacity. It is thought that visual information can be stored independently in long term memory, but that visual information is usually recoded into verbal information to put into the phonological store. As we have gained language, we inevitably link words to our images, which then activate the phonological loop (Dehn 2008: 21).
When we are babies we think in images as we have no language to name things, so the visuospatial sketchpad will be the main memory system (Mortimore 2008:107, 2001). Gradually, lexical and semantic knowledge is built through listening to others, speaking and eventually learning to read. The words are then mapped onto the image. The process of learning to read begins in picture form. The earliest record of written language is in picture form, but as communication became more precise it was impossible to decipher an exact meaning from one picture, so gradually symbolic logograms were developed which evolved into the alphabet (Adams 1998:15 – 20).
McLoughlin and Leather include artistic ability and visuospatial skills as a positive characteristic of dyslexia, but underline that this is speculation and anecdote, rather than being evidenced (2013:14). Psychologist and dyslexia researcher John Everatt, (1997) cites that Aaron and Guillemord (1993), Edwards (1994) and Vail (1990) have argued that dyslexics do have superior visual skills. Everatt, in a controlled study, did not find proof of this, but did find that dyslexics had higher creativity scores compared with his controls (1997: 20). Fellow psychologist and dyslexia researcher Beverly Steffert and Everatt found that there was: ‘...evidence of greater creativity in tasks requiring novelty or insight and more innovative styles of thinking’ (1999: 28). In their final
discussion they pose the question that those with dyslexia have had to develop innovative creative skills to overcome their disabilities.