A brief history

The majority of children learn to read and spell easily while others experience great difficulty. The nature and causes of these difficulties have been the focus of attention since the 19^th Century British doctor W. Pringle Morgan wrote about Percy, a 14-year old student who was bright and achieving typically in other subjects, but who had a severe reading disability. Pringle Morgan could find no physical evidence for this specific weakness and therefore proposed a difficulty in storing visual representations of words as the cause. The Scottish ophthalmologist James Hinshelwood held a similar view of specific reading disability, for which he coined the term “congenital word blindness”.

The idea that problems with reading were somehow visual in nature influenced the neurologist Samuel T. Orton who, in 1925, published a monograph that still influences public (but not academic) thinking about reading difficulties to this day. Orton introduced the term “strephosymbolia” (twisted symbols) to describe what he believed to be a perceptual disorder in which the individual tended to perceive visual symbols as reversed images (e.g., the classic b as d or was as saw). The resulting errors were believed to be of visual perception along with letter orientation and letter sequencing errors in reading and writing.  

These early ideas of reading difficulties being due to primary vision (word blindness) or visual perceptual (strephosymbolia) impairments remain influential in the public mind, yet they are almost certainly false and have been known to be so for 30 years. In a series of studies in the 1970s Frank Vellutino and his colleagues compared the performance of dyslexic and normal readers on various tasks measuring visual memory, spatial orientation, and visual sequencing (e.g., b, d, p, q, was, saw, loin, lion). They found that there was no difference between the groups when the tasks required a written as opposed to a verbal response, which suggested that the dyslexics’ problems were related to verbal rather than visual functions.

Perhaps the most convincing evidence from these studies was that the dyslexic groups made no more ‘visual’ errors than the good readers when the letters and words were taken from the Hebrew language which was foreign to both groups. Thus, the problem faced by individuals with dyslexia is likely to be verbal in nature, not visual, and the ‘visual’ errors they make are due to lack of familiarity with the written language rather than to “word blindness” or visual perceptual problems.

Terminology

Many different terms have been used to describe dyslexia, including:

• (specific) reading disability,
• reading difficulty,
• poor reader,
• atypical reader,
• struggling reader,
• retarded reader,
• low progress reader,
• reading impaired,
• reading disorder,
• and the general term ‘learning difficulty’.

Each of these terms has its own special problems and we prefer to use the term dyslexia. Implicit in most formal definitions of dyslexia is the notion that the reading difficulties are somehow constitutional or biological in origin and that they are not caused by more general learning difficulties, such as low IQ or language impairment. While the idea that dyslexia is biological is in some ways supported by the genetics research (see below), the practical application of genetic tests in clinical practice is some way off. There are also very valid concerns about the use of IQ scores in defining dyslexia given that the association between IQ and reading is modest and that there is no practical method of separating between ‘high-functioning’ poor readers and those poor readers with lower IQs. That poor reader suppresses IQ scores over time adds another layer of concern.  At Understanding Minds we take a more pragmatic approach.

The word dyslexia comes from the Greek roots dys meaning poor and lexia meaning words and it literally means “poor with words”. If we accept this literal interpretation then anyone who has difficulty with words is dyslexic. However, when deciding if the label will be useful for the child or family we consider the following model (see Figure 1).

Figure 1 shows graphically the Simple Model of Reading. The Simple Model holds that reading comprehension (the end goal of reading) is a function of one’s ability to read the words on the page (word-reading) and the ability to apply linguistic and reasoning skills to the decoded text (broader language skills in the model).

This model produces four broad groups of readers:

1. skilled readers,
2. those with poor comprehension (i.e., they are adequate word-readers and probably sound quite good when teachers take a running record or when parents listen to them read a familiar book; however, they have poor linguistic comprehension and verbal reasoning skills which result in poor comprehension),
3. those who have more global language impairment (i.e., they struggle with word-reading and, even if they could read the printed words, they would have difficulty deciphering the meaning of the text), and
4. those with dyslexia who have difficulty with word-level reading, yet who would have good comprehension if they could read the words on the page.        

 
Figure 1 - A simple model of reading

Dyslexia then is a specific problem with word-level skills (see the Reading section of the FAACT Model for a full description of how word-level reading skills develop). When taken literally, those individuals who fall in to the bottom-left box (Specific Language Impairment) of the Simple Model could also be argued to be dyslexic; after all they are poor with words. However, their problems can be better described under the label of global language impairment. It serves no useful purpose to describe them as dyslexic.

Other Characteristics

Although dyslexia is at the core a problem with word-level reading, it is worth noting that research has shown that groups of people with dyslexia tend to do more poorly on a variety of non-reading measures. These include tasks of visual-spatial perception, working memory, motor skills, sensitivity to high frequency patterns, and sensory processing tasks. These group differences have led to some theories or beliefs about dyslexia that are manifestly untrue and which have caused harm to some children with dyslexia and to their parents’ hip-pockets. Examples of these theories include:

• that dyslexia is synonymous with Irlen-Meares Syndrome (visual discomfort) and that it can be cured with coloured glasses,
• that visual processing deficits are the cause of dyslexia and that behavioural optometry represents a cure (see the Research & Articles page for a review of vision and dyslexia),
• many children with dyslexia have co-morbid coordination problems that are often manifested in early school life as problems with writing. Time is often spent unnecessarily on occupational therapy to treat the motor problem in the mistaken belief that improvements in reading and writing will follow,
• that dyslexia is somehow ‘auditory’ and that it will respond to various listening programs or programs purporting to emphasise ‘central’ auditory processing.   

The simple facts of the matter are that beyond a core word-level weakness all individuals with dyslexia are different. If we took 100 people with dyslexia and 100 good readers and put them in a room together, the dyslexics would be as different from each other as they would be from the good readers. Some would be creative, others not. Some would be good at sport, while others would be uncoordinated or show no interest. Some would have high IQ and some only modestly endowed, some would have exceptional vocabulary and some modest word knowledge. Some would have used their compensatory skills to become adequate readers over time, while others would remain poor readers.   

It is these individual differences that mean it makes no logical sense to begin a sentence with dyslexia is…People with dyslexia must be treated as individuals and their strengths and weaknesses beyond the core word-level weakness mapped and managed or promoted.