Current scientific knowledge about dyslexia

Although we are far from a complete scientific understanding of dyslexia, and the field has its fair share of controversies and competing theories, nevertheless we know enough to be able to formulate with confidence a computerised test that will screen effectively for dyslexia in adults.

Current research evidence points very strongly to dyslexia being a constitutional disorder that is usually inherited genetically and which arises largely because of weaknesses or differences in cognitive systems that subserve processes used in the perception and production of speech, including phonological processing, lexical access and working memory (for reviews see Miles and Miles, 1999; Snowling, 2000). Phonological processing refers to the processing of information concerning the sounds of language, at the levels of phonemes, spoken words and syllables, and the integration of these with other cognitive representations, such as graphemes (letters) and written words. Lexical access is the process by which we locate stored representations of words in a mental lexicon held in long-term memory. Working memory is the process by which we can hold phonological information in a short-term memory store while we carry out some mental operation on it, such as recognising a word we have heard or read. All these processes are critical to reading, writing and spelling.

Tasks that involve decoding or encoding of individual words at a phonological or lexical level are those most notably affected in dyslexia, but any task involving speed of processing (see Wolf and O’Brien, 2001), rapid recall of rote information, or which places heavy demands on working memory is likely to be impaired. Intelligence, reasoning and problem solving skills are not directly affected, but may be indirectly affected in speeded tasks or those involving rote recall.

Although the phonological deficit is undoubtedly the predominant theory of dyslexia at the present time, there are alternative theories, which implicate deficits in visual processing (see Stein et al, 2001), and automatisation of skills due to deficits in cerebellar processing (see Fawcett and Nicolson, 2001). It remain to be seen whether the dysfunctions referred to in these theories are best understood as subtypes of dyslexia or, alternatively, as different conditions altogether.

Dyslexia affects about 4% of the population fairly severely, while up to about another 6% may experience dyslexic difficulties of a less severe nature. In childhood, early difficulties with phonology are common in individuals with dyslexia, and at primary school problems with acquiring phonic decoding skills almost universal. The dyslexic child is normally late in learning to read and rate of reading generally remains slow in comparison with peers. Written construction and spelling are among the most difficult activities for dyslexics, and typically these remain life-long weaknesses, although the word processor has enabled many people with dyslexia to write with greater confidence. In addition to slow reading speed and difficulties with writing, limitations in speeded processing tasks and recall of information learned by rote all combine to create major problems for dyslexic people in examinations. To make assessment of learned skills fairer for people with dyslexia than they otherwise would, it has become the norm to allow additional time in written examinations, such as GCSE, ‘A’ level and degree exams. This issue is discussed more fully in Chapter 4.

As people with dyslexia grow up they usually develop a variety of compensatory strategies, some of which are positive tactics to help them to meet the educational or occupational demands placed upon them, while others are simply means of concealing their difficulties (see McLoughin, Fitzgibbon and Young, 1994). But although dyslexia is a life-long condition, it is not an inevitable barrier to educational or occupational achievement. The number and proportion of students with dyslexia entering higher education is steadily increasing, and although they may have to work much harder than other students, there is evidence that their degree results are just as good (see Singleton, 1999). In almost all occupations there are now highly successful individuals with dyslexia, and in recent years dyslexia has become less socially stigmatised. Support for dyslexic adults in the workplace is more forthcoming (see Bartlett and Moody, 2000; Reid and Kirk, 2001; McLoughlin, Leather and Stringer, 2002) Nevertheless, one should not underestimate the personal difficulties of adults with dyslexia, struggling to cope in a literate world (see Miles and Varma, 1995; Riddick, Farmer and Sterling, 1997). Dyslexia is never entirely overcome, but people can and do come to terms with it and live happy and successful lives.

However, recent independent research studies have indicated that dyslexia is three to four times more common amongst prisoners and offenders than in the general population (BDA, 2005; Dyslexia Institute, 2005). Dyslexia increases the risks of people failing educationally, of leaving school without qualifications and consequently struggling to find employment – factors that are all associated with offending. When dyslexia remains undetected and unaddressed the person does not simply lack the ability to read and write. There can also be huge emotional burdens because the person does not understand their learning difficulties. Hatred of school and teachers easily develops into resentment of society and indifference to others. Current policy initiatives such as the The Offender’s Learning Journey (DfES, 2004) acknowledge that identifying dyslexia amongst offenders and providing appropriate educational and psychological support is important in strategies to reduce reoffending.