Reversing letters and reading transformed text in dyslexia: A reassessment

The visual deficit hypothesis of development dyslexia has largely been abandoned because many of the phenomena that initially motivated it could not be replicated under controlled experimental conditions, while phonological processing deficits were found to provide a better explanation for the replicable phenomena. Nevertheless, many teachers and special educators continue to subscribe to the hypothesis that deficits of visual perception are a major cause of reading failure in dyslexia. As part of a larger family study, we reexamined the questions (1) whether probands and affected relatives in dyslexia families reverse easily confused letters more frequently under experimental conditions than normal readers from the same families, and (2) whether they show unusual facility in reading geometrically transformed text. The findings indicated that young dyslexia students reverse easily confused letters more often than normal readers. Reading group differences of letter reversal were significant in children from 7–10 years but not thereafter; and virtually no subject reversed letters when spelling whole words. Furthermore, dyslexic persons in every age group from 7–60 years actually took longer than normal readers to decode geometrically transformed text; and the time to decode transformed texts increased progressively with age after adolescence in both dyslexic persons and normal readers. Thus, reading group differences in decoding easily confused letters and reading geometrically transformed text do not support the visual deficit hypothesis and probably do not help to clarify the etiology of developmental dyslexia.     

Do dyslexic and other poor readers differ in reading-related cognitive skills?

The rationale for the study was that if dyslexic and garden-variety poor readers differ in reading-related cognitive skills, there is justification for believing dyslexia to be a distinct entity. Subjects were 110 children aged 6 to 10 years, divided into groups of dyslexic poor readers varying in verbal IQ, garden-variety poor readers, and good readers. Findings suggest that there are valid grounds for believing that dyslexia is a separate entity from garden-variety poor reading, and that it is found among children at all verbal IQ levels. Poor phonological awareness and nonword reading, in relation to normal readers, were shared by dyslexic and garden-variety poor readers. Deficits unique to dyslexic poor readers were problems in both automatic visual recognition and phonological recoding of graphic stimuli. The study supports the phonological-core variable-difference model of Stanovich (1988) in that both dyslexic and garden-variety poor readers showed phonological processing deficits, but they were more extensive in dyslexics.     

Visual and Auditory Information Processing in Dyslexia: The Possibility of Subtypes

THIS DOUBLE‐BLIND experiment investigated various aspects of visual and auditory problems related to dyslexia. Seventeen children with dyslexia aged 7.25 to 10.25 years were compared with 17 normal readers matched for CA and intellectual ability. A speech perception task which measured the subjects’ auditory threshold level significantly separated the two groups. No difference was found when this task was performed at 35 dB above individual threshold levels. A significant difference between groups was found for the Form Constancy Subtest of the Frostig Developmental Test of Visual Perception (DTVP) (1966). A significant negative correlation found between these measures for the dyslexics, but not for the normal readers, supports previous evidence for auditory and visual subtypes in dyslexia. Various optometric measures were also examined. Four dyslexics, but no normal readers, suffered fixation disparity. This difference was significant. Six representative subjects of each group were compared for eye tracking in reading. The word span of the dyslexics was significantly smaller than that of the normal readers. A multiple discriminant analysis incorporating the auditory threshold task, form constancy, fusional reserves (distance, negative), accommodation right eye and heterophoria significantly discriminated the two reading groups. The perceptual variables were more heavily weighted than the optometric measures. It was concluded that while eye tracking and binocular fusion problems should always be considered in the assessment of dyslexics, factors involved in information processing in auditory and visual perception appear to be those which are more highly implicated.     

Is there a thing called dyslexia?

A controversy whether developmental dyslexia is qualitatively different from other forms of reading disability has existed among reading specialists for many years because poor readers, regardless of the labels attached to them, resemble each other symptomatically (i.e., in reading achievement). For this reason, it is difficult to establish a priori criteria based on symptoms to identify dyslexia and compare it with other forms of reading disability. One possible solution to this impasse is to see if poor readers differ in the etiology of their reading disability and, if they do, then to see whether one group of poor readers fits the traditional definition of dyslexia. This strategy was adopted in the present study. In this paper, it was hypothesized that the etiology of dyslexia is different from that of other forms of reading disability because there is a difference in the components that malfunction in dyslexia and other forms of reading disability. Studies have shown that the two components that account for a large proportion of variance in reading are decoding and comprehension. Previous studies also indicate that dyslexic children are deficient in decoding skills but not necessarily in comprehension. In this study, reading-disabled children were divided into two groups on the basis of their listening comprehension. Children whose listening comprehension was at or above grade level were placed in one group; poor readers with below-grade-level listening comprehension were placed in the second group. Both groups, however, were matched for reading comprehension. The two groups and a control group of normal readers were administered a number of tasks that were designed to assess the efficiency of the components of reading. It was found that poor readers with normal listening comprehension were deficient in tasks that involved grapheme-phoneme conversion (Component I, decoding). When tested on tasks that minimized decoding requirements, their reading comprehension was comparable to that of normal readers. In contrast, the group with sub-average listening comprehension was poor in measures of reading comprehension, even when decoding requirements were minimal. With the exception of very few children, this group also had adequate decoding skills. Because poor readers with normal listening comprehension had average or above average IQ, they conform to the traditional definition of dyslexia. Poor readers with below average listening comprehension had below average IQ and could be considered as “general reading backward.” It was, therefore, concluded that the etiology of developmental dyslexia is different from that of general reading backwardness. In this paper, the termetiology refers to proximal causal factors such as decoding and comprehension and not to distal causal factors such as genetic and neurological characteristics.     

Antecedents to reading disability: Preschool language development and literacy experiences of children from dyslexic families

In a longitudinal study of the relation between preschool development and later reading abilities, children with dyslexic parents and/or older siblings were compared to children with no family incidence of dyslexia. Many children from dyslexic families developed reading problems by the end of the second grade, and these poor readers were characterized chiefly by weaker early syntactic and phonological skills and by less frequent exposure to books during their preschool years than the preschoolers who became normal readers. Some implications of the results for etiological theories of dyslexia are discussed.     

Developmental dyslexia: Is it different from other forms of reading disability?

A controversy whether developmental dyslexia is qualitatively different from other forms of reading disability has existed among reading specialists for many years. In the present study, the hypothesis that the etiology of dyslexia is different from that of other forms of reading disability because of differences in the components that malfunction was tested. A number of studies have shown that the two components that contribute to a large proportion of variance in reading are decoding and comprehension. It is, therefore, possible that a breakdown of different components could lead to different forms of disabilities. College students who were poor readers were assigned to two groups on the basis of their IQ. Conforming to the traditional criterion of dyslexia, those who had an IQ of 95 and above were considered as dyslexic. Those who had an IQ of 85 or below were placed in the Nonspecific Reading-Disabled group. These two groups of poor readers and a group of normal readers were administered a large number of reading-related tests. It was found that the two reading-disabled groups differed from each other in six of the seven areas assessed. There was very little overlap of scores between the two groups in these areas. The results were interpreted to suggest that poor decoding skill is the etiology of developmental dyslexia and that it differs from other forms of reading disability which are caused by generalized cognitive deficits.     

Dyslexia and sequential order errors in reading

This paper reports a study of the antecedent-consequent model of reading dysfunction and possible relationships between verbal spatial order memory and sequence errors in word reading. It provides data on the nature and frequency of such errors. Performance by normal and dyslexic readers on a number of tasks was compared. The study supports the hypothesis that sequence errors of dyslexic readers are related to a developmental lag. This research was carried out in partial fulfillment of the requirements for the Ed.D. at the University of Rochester. The author would like to express appreciation to Drs. Keith Rayner, Harry Reis, Ellsworth Woestehoff, Frank Greene and Achilles de Berardinis for their advice and assistance in the study.     

The Contribution of Visual Sensitivity,Phonological Processing,and Nonverbal IQ to Children's Reading

It has been suggested that the differences observed for dyslexic readers compared to normal readers on tasks measuring visual sensitivity may simply be the result of differences between the two groups in general cognitive ability and/or attentional engagement. One common way to accommodate this proposal is to match normal and dyslexic readers on IQ. However, an explicit test of this suggestion is to take normal and dyslexic readers who differ on IQ—where IQ would be expected to explain reading ability—and determine if visual sensitivity can still account for reading skill, even when IQ is taken into account. In this study we explored the relative contributions of nonverbal IQ, visual sensitivity as measured by sensitivity to the frequency doubling illusion, and phonological and irregular word reading to reading ability. Visual sensitivity explained a significant amount of variance in reading ability, over and above nonverbal IQ, accounting for 6% of the unique variance in reading ability. Moreover, visual sensitivity was related primarily to irregular word reading rather than to nonsense word decoding. This study demonstrates that low-level visual sensitivity plays an intrinsic role in reading aptitude, even when IQ differences between normal and dyslexic readers are contrived to maximize the contribution of IQ to reading skill. These results challenge the suggestion that impaired visual sensitivity may be epiphenomenal to poor reading skills.     

Syntactic and discourse skills in Chinese adolescent readers with dyslexia: a profiling study

This study aims to investigate the relation of syntactic and discourse skills to morphological skills, rapid naming, and working memory in Chinese adolescent readers with dyslexia and to examine their cognitive–linguistic profiles. Fifty-two dyslexic readers (mean age, 13;42) from grade 7 to 9 in Hong Kong high schools were compared with 52 typically developing readers of the same chronological age (mean age, 13;30) in the measures of word reading, 1-min word reading, reading comprehension, morpheme discrimination, morpheme production, morphosyntactic knowledge, sentence order knowledge, digit rapid naming, letter rapid naming, backward digit span, and non-word repetition. Results showed that dyslexic readers performed significantly worse than their peers on all the cognitive-linguistic tasks. Analyses of individual performance also revealed that over half of the dyslexic readers exhibited deficits in syntactic and discourse skills. Moreover, syntactic skills, morphological skills, and rapid naming best distinguished dyslexic from non-dyslexic readers. Findings underscore the significance of syntactic and discourse skills for understanding reading impairment in Chinese adolescent readers.     

Gender ratio and cognitive profiles in dyslexia: a cross-national study

The purpose of this study was to analyze possible gender-related differences in the prevalence of dyslexia. A cross-national comparison of Spain and Guatemala was conducted. Both countries speak the same language but have a different standard of living and educational level. A second purpose of this study was to analyze the cognitive profile of Guatemalan and Spanish males and females children with dyslexia. The log-linear analysis indicated that the number of dyslexics detected was different across the countries but there were no differences as a function of gender. Similarly, there were no significant or meaningful differences between dyslexic males and females in the cognitive processes involved in reading. Therefore, gender differences do not appear to be characteristic of developmental dyslexia.     

Is dyslexia a form of specific language impairment? a comparison of dyslexic and language impaired children as adolescents

Two groups of adolescents with a childhood history of language impairment were compared with a group of developmentally dyslexic young people of the same age and nonverbal ability. The study also included two comparison groups of typically developing children, one of the same age as those in the clinical groups, and a younger comparison group of similar reading level to the dyslexic students. Tests of spoken and written language skills revealed that the adolescents with dyslexia were indistinguishable from those with resolved language impairments on spoken language tasks, and both groups performed at age-expected levels. However, both dyslexic readers and those with resolved specific language impairments showed deficits in phonological awareness. On written language tasks, a different pattern of performance was apparent. In reading and spelling, adolescents with dyslexia performed only as well as those with persistent oral language impairments and younger controls. However, their reading comprehension was better. The theoretical and educational implications of these findings are discussed.     

Dyslexia: Symbol processing difficulty in the Kannada language

The purpose of this study was to investigate whether among children who speak Kannada, a Dravidian language from South India, there are those who show the same pattern of specific dyslexia as has been found to occur in children who speak European languages. The performances of 14 dyslexic children, aged between 8 and 10 years, whose native language was Kannada, were compared on a variety of tasks with fourteen normal readers and fourteen non-dyslexic poor readers. There were no significant differences between the three groups on tests of visual discrimination, visual recognition, visual recall, memory for shapes in sequence, or auditory discrimination. There were differences, however, between the dyslexics and the normal readers on tests of recall of auditorily presented digits, word analysis, word synthesis, and on two tests of visual-verbal association. The non-dyslexic poor readers were more similar to the dyslexics on recall of auditorily presented digits and word synthesis but more similar to the normal readers on word analysis and on the two tests of visual-verbal association. It is argued that these results are evidence of a consistent pattern in specific dyslexia which does not depend on any one writing system or geographical location.     

Ocular dominance,reading and spelling: a reassessment of a measure associated with specific reading difficulties

The association of reading disability with perceptuomotor problems has had a chequered history. This study examines the relationship between a new test of ocular dominance and reading and spelling ability in a group of 323 schoolchildren. Similar rates for unfixed ocular dominance were found for poor readers as in comparable studies. The rates of unstable ocular dominance did not differ between those with reading and spelling difficulties and controls. These findings in a ‘blind’ study question the role of this test of eye dominance as a diagnosis of ‘dyslexia’.     

Word length and word frequency affect eye movements in dyslexic children reading in a regular (German) orthography

We combined independently the word length and word frequency to examine if the difficulty of reading material affects eye movements in readers of German, which has high orthographic regularity, comparing the outcome with previous findings available in other languages. Sixteen carefully selected German-speaking dyslexic children (mean age, 9.5 years) and 16 age-matched controls read aloud four lists, each comprising ten unrelated words. The lists varied orthogonally in word length and word frequency: high-frequency, short; high-frequency, long; low-frequency, short; low-frequency, long. Eye movements were measured using a scanning laser ophthalmoscope (SLO). In dyslexic children, fixation durations and the number of saccades increased both with word length and word frequency. The percentage of regressions was only increased for low-frequency words. Most of these effects were qualitatively similar in the two groups, but stronger in dyslexic children, pointing to a deficient higher-level word processing, especially phonological deficit. The results indicate that reading eye movements in German children are modulated by the degree of difficulty, and orthographic regularity of the language can determine the nature of modulation. The findings suggest that, similar to Italian but unlike English readers, German children prefer indirect sub-lexical strategy of grapheme-phoneme conversion.     

An interaction-dominant perspective on reading fluency and dyslexia

The background noise of response times is often overlooked in scientific inquiries of cognitive performances. However, it is becoming widely acknowledged in psychology, medicine, physiology, physics, and beyond that temporal patterns of variability constitute a rich source of information. Here, we introduce two complexity measures (1/f scaling and recurrence quantification analysis) that employ background noise as metrics of reading fluency. These measures gauge the extent of interdependence across, rather than within, cognitive components. In this study, we investigated dyslexic and non-dyslexic word-naming performance in beginning readers and observed that these complexity metrics differentiate reliably between dyslexic and average response times and correlate strongly with the severity of the reading impairment. The direction of change in the introduced metrics suggests that developmental dyslexia resides from dynamical instabilities in the coordination among the many components necessary to read, which could explain why dyslexic readers score below average on so many distinct tasks and modalities.     

The Use of Sublexical Clusters in Normal and Dyslexic Readers

The current study examined the use of sublexical clusters in normal and dyslexic readers. We focused primarily on onset consonantal clusters, but the use of rimes and digraphs was also considered. A segmentation paradigm, the separation of two adjacent letters in a word by a nonletter symbol, was used. We hypothesized that the effect of this distortion on reading would be larger if two adjacent letters functioned as a cluster. In the first study, naming and lexical decision tasks were administered to 24 normal reading and 24 dyslexic fourth-grade children. In a second study, the same tasks were administered to 24 skilled adult readers. The results did not support the use of consonantal onsets and rimes during reading. However, we did find that digraphs were used, because their distortion had a relatively large effect on reading speed. This effect was similar in normal and dyslexic readers.     

Spatial selective attention and asynchrony of cognitive systems in adult dyslexic readers: an ERPs and behavioral study

The aim of this study was to gain additional knowledge about the asynchrony phenomenon in developmental dyslexia, especially when spatial selective attention is manipulated. Adults with developmental dyslexia and non-impaired readers underwent two experimental tasks, one including alphabetic stimuli (pre-lexical consonant–vowel syllables) and the other containing non-alphabetic stimuli (pictures and sounds of animals). Participants were instructed to attend to the right or left hemifields and to respond to all stimuli on that hemifield. Behavioral parameters and event-related potentials were recorded. The main finding was that the dyslexic readers demonstrated asynchrony between the auditory and visual modalities when alphabetic stimuli were presented on the right hemifield. These results suggest that intact reading is linked to a synchronized auditory and visual speed of processing even when spatial selective attention is manipulated. The findings of the current study are discussed in terms of asynchrony between modalities as a neurocognitive marker in developmental dyslexia.     

How does reading performance modulate the impact of orthographic knowledge on speech processing? A comparison of normal readers and dyslexic adults

Studies on proficient readers showed that speech processing is affected by knowledge of the orthographic code. Yet, the automaticity of the orthographic influence depends on task demand. Here, we addressed this automaticity issue in normal and dyslexic adult readers by comparing the orthographic effects obtained in two speech processing tasks that are or not sensitive to strategies developed by participants. Our finding showed that while participants’ performance in a metaphonological task, which is known to be strategy prone, was affected by their orthographic knowledge regardless of the childhood diagnosis of dyslexia or of their actual reading-related skills, this latter factor significantly modulated the orthographic influence found in a more natural speech recognition task. The finding supports the claim that while any individuals who know a reading code are able to resort to their orthographic knowledge when they process speech, a more profound modification of the speech processing system by the orthographic code takes place only in readers who have reached a certain level of reading expertise.     

Adult developmental dyslexia in a shallow orthography: Are there subgroups?

The existence and stability of subgroups among adult dyslexic readers of a shallow orthography was explored by comparing three different cluster analyses based on previously suggested combinations of two variables. These were oral reading speed versus accuracy, word versus pseudoword reading speed, and phonological awareness versus rapid naming. The three analyses were conducted with the same group of dyslexic adults. Each analysis produced three subgroups, corresponding to ones previously suggested in the literature. However, the subgroups had only little overlap from one analysis to another. Each clustering produced somewhat different subgroup profiles in phonological processing, reading, intelligence, temporal acuity, and sensory short-term memory. However, the shared difficulties of the solutions in several language-related and sensory tasks suggest the conclusion that developmental dyslexia does not causally consist of subgroups, at least in shallow orthographies. Further, the shared sensory difficulties suggest that impaired temporal acuity and sensory short-term memory may reflect the severity of a primary disorder that dyslexic readers cannot compensate by strategies.     

Qualitative and quantitative differences among dyslexic,normal, and nondyslexic poor readers

This study tested the hypothesis that when a stringent criterion of normal IQ is applied in the selection of dyslexic readers, and when dyslexics, nondyslexic poor readers, and normal readers are matched on reading comprehension — rather than word reading — significant differences among these groups can be demonstrated. Two groups of poor readers from primary grades, one with normal IQ (dyslexics) and the other with below-average IQ (nonspecific reading disabled, NSRD) were matched for reading comprehension with a group of younger normal readers. The dyslexic group was found to be inferior to the other two groups in tests of decoding and spelling. The dyslexic readers were more context-dependent for word recognition than the other two groups. The NSRD group did not differ from the normal readers in these aspects but had the worst performance on a test of inferential comprehension. It was concluded that dyslexics differ from normal readers and low-IQ poor readers in word and nonword reading skills and context-dependency for reading. A group of six adult dyslexics were also found to be deficient in decoding skills. A lack of unanimity in the use of certain terminology, a substantial age difference between low-IQ poor readers and normals, and the difference in the criteria used for matching the different groups could be factors that can explain the disagreements seen between the findings of the present study and those reported by some other studies. Potential problems associated with reading-age matched experimental design are discussed.