Presentation on theme: "PS2011 & PS2016 Cognitive Psychology – Dr John Beech Developmental Dyslexia."— Presentation transcript:
PS2011 & PS2016 Cognitive Psychology – Dr John Beech Developmental Dyslexia
2 Definitions of dyslexia Definitions Hinshelwood (1900): “word blindness”. Orton (1937) “strephosymbolia” (“turning of symbols”). “Dyslexia” - late 19th C: German dys “difficult” and Greek lexis “speech”. Made popular by Samuel Orton, a neuropathologist. “Dyslexia” means that a child is: 1.Below normal in reading “age”. 2.In average range of IQ. 3.No visual nor auditory problems. 4.Emotionally stable. 5.Normal educational opportunity.
3 Definitions of dyslexia The term “dyslexia” can also be applied to adults in the context of their reading level being below what would be expected for their level of IQ. Dyslexia in children is referred to here as “developmental dyslexia” to differentiate from “acquired dyslexia”, which we’ll examine briefly after the current topic.
4 Definitions of dyslexia Vellutino (1979) suggested for experiments: 1.2 years behind in reading 2.WISC-R: >90 (Mean 100) 3.Acuity in sight and hearing 4.Not maladjusted 5.Only from middle class areas These are exclusionary criteria
5 Definitions of dyslexia Nowadays for assessment purposes in UK: 1. Statistically significant discrepancy on WORD reading tests on expected v. observed scores, based on the WISC-IV. Known as the “discrepancy measure” to obtain dyslexia. 2. No problems in sight, hearing or maladjustment Thus there is a little bit of confusion with the use of the term “dyslexia”. The educational establishment in the UK can tend to lump in children who are behind in reading, who are also weak in IQ.
6 Characteristics of dyslexia Some reported characteristics 1.4:1 boys:girls 2.Problems with time, naming sequences (e.g. months) 3.Left/right reversals (e.g. was/saw, b/d, p/q) 4.Problems with differentiating the left from the right 5.Difficulty in repeating things 6.Problems in understanding spoken directions 7.Problems in remembering what has just been said 8.Poor handwriting 9.Minor neurological impairments
7 Characteristics of dyslexia Is dyslexia anything special? It sounds like a medical label, but doesn’t explain the condition. All it does is exclude possibilities. Dyslexia has not been conclusively linked to brain damage so far, except that there is more brain symmetry in poor readers. But 35% of everyone has this. The rationale behind dyslexia is that if a child is poor at reading AND has normal or above average IQ, then that child has dyslexia. But outside the frame of dyslexia is the child who is poor at reading AND has low IQ. We would expect reading to be poor if IQ is also low – as shown in the Isle of Wight study…
8 Characteristics of dyslexia Isle of Wight study (Michael Rutter et al., 1970; Rutter & Yule 1975) Examined all 9-11 yrs children on Isle of Wight Correlation between mental age and reading: r = 0.6. They found that 6.6% with reading difficulties when they used the criterion of being 2yr 4mth behind chronological age in reading age. They produced 2 distinct groups among this 6.6%. One group they defined as “backward readers” with low IQ and another group were called “specific reading retarded (SRR)” who were also poor readers, but by contrast had reasonable IQ.
9 Characteristics of dyslexia Isle of Wight study (Michael Rutter et al., 1970; Rutter & Yule 1975) By taking out the low IQ backward readers from this 6.6% Rutter et al. were left with 3.7% who were SSRs. These were children who were at least 2 yr 4mth behind in their reading age, but within the average range of IQ or above average in IQ.
10 Characteristics of dyslexia Isle of Wight study (Michael Rutter et al., 1970; Rutter & Yule 1975) The frequencies of SSRs were plotted against their reading scores. They found a “hump” at the bottom of the curve. There were more than would be expected with very poor reading scores. Both backward readers and SRRs had a family history of problems in reading and speech delay and current speech problems. These problems were 3 times greater than the rest.
11 Characteristics of dyslexia Rutter and Yule did not think they’d identified “dyslexia”. They did not see it as single disorder with a genetic component. They noted great regional variations in the incidence of SRR, suggesting an environmental incidence. Despite this, educators cite this study as evidence for dyslexia. Some people would argue that there is not a biological connection with dyslexia. However, there is a connection between genetics and phonological processing weakness. There is a continuum of phonological weakness and not all individuals who are weak have problems in reading. They may well have had a good education to overcome their potential reading difficulties.
12 Dyslexia: prognosis Can children with dyslexia eventually recover? Rayner et al. (1989) studied a professor (SJ) in the USA who’d been classified as a developmental dyslexic. So here’s one case showing that it’s possible to become a fluent reader, and in this case to became a professor. Felton, Naylor and Wood (1990) studied 115 adults who had their reading well-documented in childhood. These made 3 groups: 37 were reading disabled in childhood, 38 had been borderline 40 had had no reading difficulties (37 + 38 + 40 = 115).
13 Dyslexia: prognosis The table shows, for example, that 18 children who were reading disabled (RD) remained so when adults; but 10 children who were RD became borderline readers when adult, and 9 who were RD actually grew up to become average readers. As children Reading disabled Border As adults Still RD18- Border109 Average929
14 Dyslexia: prognosis As shown in the previous table, Felton et al. demonstrated that of 37 who were RD in childhood, 19 (51%) left that category in adulthood. The situation is even better for those children who were borderline as 29 out of 38 (76%) were fluent readers in adulthood. Felton et al. also found that nonword reading (e.g. blant, gront) and manipulation of phonemes much worse for adults who were still RD, even controlling for IQ and SES. This suggests that these had problems with phonology.
15 Dyslexia v. “garden variety”: worth the distinction? Both types have the same phonological deficits when equalised on word recognition (Stanovich & Segal, 1994). Matching both types on chronological age rather than reading, shows even greater similarity (Fletcher, et al., 1994). There may be special cases, but there is substantial evidence against dyslexia being a unique syndrome. Another problem is the use of IQ as a basis for calculating “potential”. Many think of IQ as multidimensional rather than unitary. The conventional IQ test may be too narrow. Both types require the same kind of reading instruction. And importantly, most or all children can learn to read well with good instruction.
16 Reading comprehension There have been attempts to look at a listening comprehension - reading achievement discrepancy. These types of readers have small differences from conventional readers (Fletcher et al, 1994). Another aspect of using an IQ basis is the child of high IQ, who has a significant discrepancy between reading performance and potential. However, in absolute terms reading may be below average. In terms of teaching this child potentially has extra reading instruction and resources over another child at the same reading level, but with average or slightly below average IQ. But the absolute level of performance is an important problem. If there are weaknesses in reading, spelling or writing, so that a child is operating below a criterion level, then that child needs to be taught these skills to the appropriate level.
17 Summary so far There is controversy whether dyslexia is a special condition in relation to other types of poor reader. A problem from the educational aspect is that it does not define a group who need a distinctive educational approach. The diagnosis may also be detrimental if it gives the impression that this is a condition that cannot be cured. It has to be said that it can also confer a sense of relief in some that a concrete diagnosis has supposedly been achieved.
18 Biological theories of dyslexia Hormonal theory Beech & Beauvois (2006) have proposed that prenatal hormonal experience in the womb can affect phonology (processing of sounds), which in turn affects reading. Those who experience more testosterone (male hormone) were found to perform worse in phonology and in audition. Genetic factors There has been much work in this area examining the inheritance of component reading skills. Also work on finding gene markers on certain chromosomes. Language areas Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) has been very useful at developing our understanding of both processes and structure in relation to dyslexia.
19 Biological theories of dyslexia The cerebellum This theory (Nicolson & Fawcett, 1990) suggests that the cerebellum, which has control over automaticity and dexterity could explain dyslexia. The cerebellum influences the processing of speech and motor control. For example, the estimation of time and balance are connected with the cerebellum. Connected with this, is the next theory:
20 Biological theories of dyslexia Magnocellular/transient systems Magnocellular theory was advocated by Stein & Walsh (1997) The magnocells—which are large neurones in the brain—control the timing of sensory and motor events. The connection with the cerebellum is that the cerebellum processes the magnocellular brain regions. Weakness in the visual magnocellular system can confuse letter order and lead to weak visual memory. Similarly there could be an analogous weakness in phonology. Many concur that this system and its implications for timing is important for accounting for dyslexia.
21 Cognitive theories of dyslexia Phonological processing We’ll deal with this in more detail later. There has been a lot of research on this with some suggesting that phonological difficulties (processing the sounds in words) are the main cause of dyslexia. But it is probably not this simple. There is a dominant view (esp. University of York) that phonology is very important.
22 Cognitive theories of dyslexia Temporal (timing) problems This can be closely connected to phonology problems as if there are problems in timing, then processing sounds is going to be difficult. Similarly, information entering the retina has to be processed rapidly and problems in timing can also be detrimental to visual processing. Visual problems There have been different kinds of theories, including problems with binocular vision and problems with forming stable fixations. There could also be confusions in letter order (e.g. girl read as ‘grill’).
23 Cognitive theories of dyslexia Working memory This retains information for a brief time while it is being processed and perhaps transferred into long term memory. Weak working memory may help to explain dyslexia. Automaticity We’ve already seen this in relation to the operation of the cerebellum, which controls automaticity. Normally when we learn a skill we become so good that we become automatic. For example, when driving. Because those with dyslexia don’t achieve automaticity, it means that they are slowed down in their processing. They may, however, achieve automaticity eventually—it just takes much longer.
24 Summary on developmental dyslexia Developmental dyslexia is considered to be a condition in which reading (and spelling) is not progressing at the same pace as other intellectual areas. Testing involves identifying cut-off points to identify the condition. But, getting a clearer cut-off means waiting longer, which also means remediation may be just slightly more difficult. There is controversy concerning the status of dyslexia, particularly as identifying the condition does not necessarily lead to a way forward for remediation. The biological factors related to dyslexia are: hormonal, genetic, the language areas, the cerebellum, magnocellular systems. The cognitive factors are not unrelated to the biological ones: phonology, timing, automaticity, visual and working memory.