Identifying dyslexia (specific learning difficulties)

What is dyslexia?

It is not possible here to give a detailed account of the nature of dyslexia. Readers are recommended to consult any one of a number of reputable texts, including Miles (1993), Miles and Miles (1999); Reid (2003), Snowling (2000) and Thomson (1993). The genetic and neurological bases of dyslexia are now well established and reflected in most current definitions of the condition. For example, the International Dyslexia Association (formerly the Orton Dyslexia Society) published the following definition of dyslexia:

"Dyslexia is a neurologically-based, often familial disorder which interferes with the acquisition of language. Varying the degrees of severity, it is manifested by difficulties in receptive and expressive language, including phonological processing, in reading, writing, spelling, handwriting and sometimes arithmetic. Dyslexia is not the result of lack of motivation, sensory impairment, inadequate instructional or environmental opportunities, but may occur together with these conditions. Although dyslexia is life-long, individuals with dyslexia frequently respond successfully to timely and appropriate intervention"

(Orton Dyslexia Society, 1994). 

However, not all authorities agree that we have sufficient evidence to produce a convincing definition of dyslexia that incorporates aetiology (as in the one given above). In 1999 a Working Party of the British Psychological Society’s Division of Educational and Child Psychology produced a report designed to help psychologists deal with the problems of how to assess children with dyslexia (British Psychological Society, 1999b). This group reviewed — albeit inconclusively — research findings and theories in the field, and decided to produce a ‘working definition’ that was free of aetiological and theoretical assumptions:

“Dyslexia is evident when accurate and fluent word reading and/or spelling develops very incompletely or with great difficulty. This focuses on literacy learning at the ‘word level’ and implies that the problem is severe and persistent despite appropriate learning opportunities. It provides the basis for a staged process of assessment through teaching.”

(British Psychological Society, 1999b, p. 8).

The intentions of the British Psychological Society’s Working Party appear to have been to produce recommendations that had a close fit with SEN Code of Practice — which, on the face of it, seems commendable — but the outcome seems to have been to muddy the waters as far as identification of dyslexia is concerned. The British Psychological Society’s Working Party definition assumes that the problem will have been picked up in the primary stage (because the difficulties will be ‘severe and persistent despite appropriate learning opportunities’) when in fact many teachers know that this does not always happen. Furthermore, dyslexia is a condition that varies in severity and its effects are likely to be more apparent when the work faced by a student gets increasingly difficult. Hence some dyslexic students, despite having difficulties in literacy, are not formally identified in the primary school because they managed to cope (perhaps because they are very bright or work unusually hard) or simply because they have never had the opportunity to be assessed by an educational psychologist or by a teacher using appropriate tests such as Lucid CoPS Cognitive Profiling System or LASS 8-11. When confronted with much harder work in secondary school, they find they cannot cope, and it may not be until this point that dyslexia is formally identified.

Characteristics of dyslexia

Dyslexia is a variable condition and not all people with dyslexia will display the same range of difficulties or characteristics. Nevertheless, the following characteristics have been widely noted in connection with dyslexia.

  • A marked inefficiency in the working or short-term memory system, which is regarded by many experts in the field as the fundamental underlying difficulty experienced by people with dyslexia (e.g. Beech, 1997; McLoughlin, Fitzgibbon and Young 1993; Rack, 1997; Thomson, 2001). Memory difficulties may result in problems of retaining the meaning of text (especially when reading at speed), failure to marshall learned facts effectively in examinations, disjointed written work or an omission of words and phrases in written examinations, because pupils have lost track of what they are trying to express.
  • Inadequate phonological processing abilities, which affects the acquisition of phonic skills in reading and spelling so that unfamiliar words are frequently misread, which may in turn affect comprehension. Not only has it been clearly established that phonological processing difficulties are seen in the majority of children with dyslexia (e.g. Snowling, 2000), but research has also indicated that this occurs in many adults with dyslexia (see Beaton, McDougall and Singleton, 1997a).
  • Difficulties with motor skills or coordination. Nicolson and Fawcett (1990, 1994) have noted that people with dyslexia can show a particular difficulty in automatising skills. Examples of failure to automatise skills in the pupil situation might be the inability to listen with understanding while taking adequate notes, or the inability to concentrate on both the spelling and the content of written work. Dyspraxia is the generic term used to cover a heterogeneous range of disorders affecting the initiation, organisation and performance of action (Ayres, 1985; Fisher et al, 1991; Ripley et al, 1997). In childhood it is sometimes referred to as developmental coordination disorder. Pupils with dyspraxic difficulties are likely to have problems with handwriting, especially for when writing for lengthy periods or under conditions of time pressure. It should be noted that by no means all pupils with dyslexia will necessarily have dyspraxic difficulties.
  • A range of problems connected with visual processing, which can affect reading generally, but especially when dealing with large amounts of text. Such problems can include binocular instability and susceptibility to visual stress (see Evans, 1997, 2001; Evans, Drasdo and Richards, 1996; Stein, Talcott and Witton, 2001; Wilkins, 1991, 1995, 2003). Visual discomfort is a generic term for the effects of hypersensitivity to the irritating effect of strong visual contrast or rapid flicker (e.g. where parallel lines of text create the appearance of a black-and-white grating or consciously or subconsciously perceived flicker of fluorescent lighting or some computer monitors). Movement and colour illusions can be perceived, or the text may appear unstable or obscured. Reading for any length of time may cause headaches and eyestrain, and so can be done only in short bursts, which can disrupt the comprehension process. In some medical conditions (e.g. epilepsy and migraine) susceptibility to visual discomfort is generally more extreme than is usually seen in cases of dyslexia (Wilkins, 1995). It should be noted, however, that although there appears to be a statistical association between dyslexia and visual discomfort, not all persons with dyslexia are highly susceptible to visual discomfort and not all persons who suffer from visual discomfort will necessarily exhibit the typical characteristics of dyslexia outlined above. There is evidence that use of coloured overlays or filters (e.g. by use of acetate sheets or tinted lenses) can be beneficial in alleviating the symptoms of visual discomfort in a fair proportion of cases (Irlen, 1991; Wilkins, 2003; Wilkins et al, 1994, 2001; Whiteley and Smith, 2001). 

Theories of dyslexia

The term ‘specific learning difficulty’ (which for a generation or more has been preferred by many educational psychologists to the term ‘dyslexia’) means little more than a discrepancy between ability and attainment. The principal difference between ‘dyslexia’ and ‘specific learning difficulty’ is that dyslexia presupposes the existence of certain cognitive deficits which are believed to underpin the condition. Such cognitive deficits (e.g. in phonological processing, memory, visual processing, or motor co-ordination) are believed to be either inherited or due to neurological anomalies which have arisen before (or during) birth or in early childhood.

There are several theories of dyslexia, which space precludes a detailed discussion of here. There is little disagreement that the condition is a neurological one, and that it has genetic causes in most cases (see Fisher and Smith, 2001). However, the exact neurological and cognitive mechanisms are still the subject of widespread research and theoretical debate (see Frith, 1997). The predominant theory is that dyslexia is due to a fundamental deficiency in the processing of phonological information — this is usually referred to as the Phonological Deficit Theory (Rack, 1994; Rack, Snowling and Olson, 1992; Snowling, 1995). This theory is supported by a wealth of research evidence (for review see Snowling, 2000) but is complicated by it does not explain all the phenomena associated with the condition (see previous section). The ‘Double Deficit’ Theory (see Wolf and O’Brien, 2001) proposes that in addition to phonological deficits, dyslexic individuals have inherent problems in processing information at speed, which interferes with many cognitive activities, including reading and writing. Prominent alternative theories include the Magnocellular Deficit Theory (see Stein, Talcott and Witton, 2001), the Cerebellar Deficit Theory (see Fawcett and Nicolson, 2001), both of which have less evidence in support, but which address particular aspects of the condition that demand further research. Of course, it may turn out that there are distinct subtypes of dyslexia, for which different causal theories may be applicable (see Stanovich, Siegel and Gottardo, 1997).

LASS 11-15 profiles and dyslexia

The chapters that follow show how LASS profiles can be used very effectively to identify dyslexia in most cases. It can be seen the composition of the LASS tests corresponds to the phonological deficit model more closely than it fits the alternative models of dyslexia. Hence it should be expected that LASS will be at its most effective in identifying students with the ‘classic’ form of dyslexia — which includes by far the majority of the group — characterised by cognitive difficulties that most notably affect the mapping graphemes onto phonemes. But LASS is actually rather broader in its scope that first might meet the eye. Since it includes a measure of visual memory measures, LASS is also adept at picking up ‘atypical’ cases of dyslexia where, instead of phonological deficits predominating, instead, the chief problem concerns visual memory. (Note, however, that LASS it will not necessarily pick up children with other types of visual processing difficulties —such as susceptibility to visual stress — for which children may need to be referred to an eye clinic for further investigation; see Evans, 2001; Wilkins, 2003). Thus in various ways LASS encompasses a wide range of psychological correlates of dyslexia which have theoretical support from different camps and consequently as an all-round screening and assessment tool it is hard to beat.

The pros and cons of the discrepancy approach

The conventional approach to identifying dyslexia is based on the principle of cognitive discrepancy (see Singleton, 1987), which maintains that a significant discrepancy between intelligence and literacy skills is prima facie evidence for specific learning difficulty; and where such discrepancy has been found, if there is also evidence of cognitive deficits in memory and/or phonological processing, this is prima facie evidence for dyslexia. Other evidence, such as a family history of similar difficulties, developmental history of speech or language problems, or particular difficulties — e.g. in acquiring phonics — would support such a conclusion.

This model – which is similar to that advocated by Pumfrey and Reason (1991), Rack (1997), Thomson (1993) and Turner (1997) – embodies the view that diagnosis of dyslexia is based on the notion of discrepancy between what the student is achieving in literacy and what they can reasonably be expected to achieve on the basis of age and intellectual ability. It is assumed that the student has experienced normal education and that the problems are not primarily due to any emotional or medical cause. This discrepancy accounts for the fact that dyslexia is typically characterised by serious and unremitting literacy problems in students who otherwise would be expected to make reasonable progress in the acquisition of literacy.

It should also be noted that the discrepancy criterion has also come under attack in recent years (e.g. Ashton, 1996; Frederickson and Reason, 1995; Nicolson, 1996; Siegel, 1989a, 1989b, 1992; Solity, 1996; Stanovich, 1991a, 1991b; see also Turner, 1997). One problem is that it is difficult to establish that a significant discrepancy exists if the student is of below average intelligence. Yet, in principle, being a constitutional condition, dyslexia can affect students of all abilities (Singleton, 1987). Furthermore, such an approach relies on waiting for the student to fail, often over many years, before action is taken. Another complication is that few, if any, real differences exist in the literacy difficulties manifested by students who do and do not display significant IQ–achievement discrepancies (Stanovich, 1991a, 1991b; Stanovich, Siegel and Gottardo, 1997).

It is well accepted that the discrepancy criterion is problematic when it comes to early identification of dyslexia (Fawcett, Singleton and Peer, 1998; Singleton, 1988), which has led to the development of alternative systems such as CoPS Cognitive Profiling System (Singleton, Thomas and Leedale, 1996, 1997), DEST (Nicolson and Fawcett, 1996), and PhAB (Frederickson, Frith and Reason, 1997). However, in the assessment of older students or adults, the abandonment of the discrepancy criterion is more controversial. A report of a working party on identification of dyslexic students, set up by the Division of Educational and Child Psychology of the British Psychological Society, noted that the discrepancy model is vulnerable to criticism on theoretical grounds and advocated a more global approach to assessment (British Psychological Society, 1999b). Nevertheless, in the classroom, it is often the case that discrepancy between a student’s expected levels of attainment (based on judgements of their overall ability) and their actual attainments (especially in reading, writing and spelling) are what first draw a teacher’s attention to the possibility that the student may have dyslexia. It therefore seems premature to abandon altogether the notion of discrepancy. Rather, discrepancy can usefully be regarded as part of the overall evidence on which a teacher makes a judgement. For these reasons, LASS 11-15 has been developed in such a way that teachers who wish to use a discrepancy approach can do so, but this does not mean that it has to be used in a manner dictated by that model. Indeed, a balanced approach to identifying dyslexia is often recommended – i.e. one that takes account of discrepancies as well as key cognitive indicators, such as phonological processing and memory. This approach is advocated by many experts in the field, including, most notably, Snowling (2000), who one of the most well-known international authorities on dyslexia. LASS has been designed to facilitate this type of balanced approach.