Phonological processing skills and deficits in adult dyslexics

This article presents 4 experiments aimed at defining the primary underlying phonological processing deficit(s) in adult dyslexia. 5 phonological processes, all involving spoken language, were studied: phoneme perception, phoneme awareness, lexical retrieval of phonology, articulatory speed, and phonetic coding in verbal short-term memory. 2 differently ascertained adult dyslexic groups, familial dyslexics (n = 15) and clinic dyslexics (n = 15), were the subjects in each experiment. These dyslexic groups were chosen because deficits that persist until adulthood and that are found in differently ascertained dyslexic groups are more likely to be primary. Each dyslexic group was compared to 2 control groups, chronological age (CA) controls who were similar in age and sex, and younger reading age (RA) controls who were similar in reading age and sex. The main finding was a clear deficit in phoneme awareness in both dyslexic groups, with each dyslexic group performing significantly worse than both CA and RA controls. Moreover, performance on the 2 phoneme awareness tasks together uniquely accounted for substantial variance in nonword reading. The clinic but not the familial dyslexics appeared to have an additional deficit in verbal short-term memory. No clear deficits were found in either dyslexic group in phoneme perception, lexical retrieval, or articulatory speed.     

Cognitive-linguistic profiles of Chinese typical-functioning adolescent dyslexics and high-functioning dyslexics

Dyslexia is a developmental disability affecting the acquisition of reading and writing skills, and its developmental nature makes longitudinal research of great importance. This study therefore investigated the cognitive-linguistic profiles of the typical-functioning dyslexics and high-functioning dyslexics with longitudinal cohorts of Chinese-speaking adolescents diagnosed with childhood dyslexia. These two dyslexic groups of fifty students (with 25 typical-functioning dyslexics) were assessed in Grade 2 (Time 1) and in Grade 8 (Time 2), whereas 25 typically developing controls were assessed at Time 2. Students were administered measures of phonological awareness, morphological skills, visual-orthographic knowledge, rapid naming, verbal working memory, and literacy skills. Results showed that, at Time 2, both dyslexic groups performed less well than the control group on most of the measures. Deficits in rapid naming were particularly salient in both dyslexic groups. Comparing the two dyslexic groups, the typical-functioning dyslexics had more multiple deficits than the high-functioning dyslexics. Findings highlight the importance of rapid naming deficits as potential universal causes of dyslexia and the utility of targeting visual-orthographic knowledge and morphological skills in supporting the development of dyslexic adolescents.     

Developmental dyslexics show deficits in the processing of temporal auditory information in German vowel length discrimination

The present study investigated auditory temporal processing in developmental dyslexia by using a vowel length discrimination task. Both temporal and phonological processing were studied in a single experiment. Seven German vowel pairs differing in vowel height were used. The vowels of each pair differed only with respect to vowel length (e.g., /a/ vs. /a:/). In German, vowel length is characterized by temporal and spectral information. Three types of differences between long versus short vowels were varied: In the phonological condition, pairs of natural vowels were used, differing in their temporal as well as in their spectral content. In two temporal conditions, in contrast, a natural vowel was always combined with a manipulated one to keep spectral content of long and short vowels identical. Thus, the only distinguishing feature between the two vowels was temporal in nature. Vowels were embedded into monosyllabic pseudo-words and presented successively in a speeded same–different task. Twenty dyslexics and twenty age-matched controls participated in the experiment. In both groups, discrimination accuracy decreased with increasing vowel height in the two temporal conditions. This result is consistent with former findings on the relevance of temporal information for vowel length identification in German and extends this topic to cover discrimination demands. In the phonological condition, groups did not differ in discrimination accuracy. In both temporal conditions, however, dyslexics performed worse than controls. These results suggest that developmental dyslexia is associated with impairments in processing basic acoustic parameters of the speech signal, in particular, with a deficit in temporal processing.     

Phonological difficulties in high-functioning dyslexics

Well compensated, high-functioning dyslexics, aged 18 years, whose reading ability had improved so that it was now within one standard deviation of the normal population mean were assessed on a range of phonological tasks. The dyslexics were compared with controls matched for age and academic attainment. A sizeable subgroup performed as well as controls on a word recognition test. However, they performed worse, in terms of accuracy, on nonword reading and spelling, and worse, in terms of speed, on spoonerisms, digit naming and speech rate. These results indicate that, even when word recognition ability has reached normal levels, a specific problem in subsyllabic phonology persists, and is demonstrable both in written and spoken language processing. Despite this specific difficulty, all the dyslexic participants were studying for university entrance exams and were expected to enter tertiary education.     

Reading strategies in Spanish developmental dyslexics

Cross-linguistic studies suggest that the orthographic system determines the reading performance of dyslexic children. In opaque orthographies, the fundamental feature of developmental dyslexia is difficulty in reading accuracy, whereas slower reading speed is more common in transparent orthographies. The aim of the current study was to examine the extent to which different variables of words affect reaction times and articulation times in developmental dyslexics. A group of 19 developmental dyslexics of different ages and an age-matched group of 19 children without reading disabilities completed a word naming task. The children were asked to read 100 nouns that differed in length, frequency, age of acquisition, imageability, and orthographic neighborhood. The stimuli were presented on a laptop computer, and the responses were recorded using DMDX software. We conducted analyses of mixed-effects models to determine which variables influenced reading times in dyslexic children. We found that word naming skills in dyslexic children are affected predominantly by length, while in non-dyslexics children the principal variable is the age of acquisition, a lexical variable. These findings suggest that Spanish-speaking developmental dyslexics use a sublexical procedure for reading words, which is reflected in slower speed when reading long words. In contrast, normal children use a lexical strategy, which is frequently observed in readers of opaque languages.     

Word processing: its impact on children's writing

This paper describes the effects of using a word processor on the creative writing of a small group of children with learning disabilities. Each week the children wrote one word-processed and one handwritten story. The effects of using a word processor seemed to be influenced by the particular problems the children were experiencing with written work. For the children with severe spelling problems, using a word processor seemed to result in fewer spelling errors, while for the children who were still predominantly concerned with the mechanics of the writing task, using a word processor seemed to result in longer stories.     

Processing of derived forms in high-functioning dyslexics

We report on an experiment designed to evaluate processing of derived forms in high-functioning dyslexics, defined as university students with a history of reading difficulties who have age-appropriate reading comprehension skills. We compared high-functioning dyslexics with a group of normal adult readers in their performance on a lexical decision task with derived items (such as cloudy and ably) and pseudo-derived items (such as belly and gravy). Some items contained an orthographic change (such as able-ably and gravy) and others did not (such as cloud - cloudy). The results indicated that although control participants’ response times varied systematically as a function of morphological complexity, those of high-functioning dyslexics did not. Further, there was some evidence of a relationship between derivational processing and reading. It seems that high-functioning dyslexics have persistent difficulties in processing one particular aspect of morphology; that of derived forms.     

The role of gene DCDC2 in German dyslexics

Dyslexia is a complex reading and writing disorder with a strong genetic component. In a German case-control cohort, we studied the influence of the suspected dyslexia-associated gene DCDC2. For the first time in a German cohort, we describe association of a 2445 basepair deletion, first identified in an American study. Evidence of association for three DCDC2 single nucleotide polymorphisms (rs807724, rs793862, rs807701), previously identified in German or American cohorts, was replicated. A haplotype of these polymorphisms showed evidence for association as well. Thus, our data further corroborate association of DCDC2 with dyslexia. Analysis of functional subgroups suggests association of investigated DCDC2 variants mainly with nondysphonetic, nonsevere, but probably dyseidetic (surface) dyslexia. Based on the presumed function of DCDC2, our findings point to a role of impaired neuronal migration in the etiology of the disease. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Spelling errors and reading fluency in compensated adult dyslexics

Generally, a person who is diagnosed as dyslexic remains diagnosably dyslexic all his/her life. However, occasionally, an individual compensates for his/her difficulties in some way, and by adulthood is no longer diagnosably dyslexic. In what ways are these compensated dyslexics different from both dyslexics and nondyslexics? We compared IQ, achievement test, and spelling error scores in adult dyslexics, adult nondyslexics, and adult compensated dyslexics (N=25) in the two studies reported here. The second study differed from the first in that the subjects were matched for age, education, IQ, and SES. In both studies, compensateds were significantly different from nondyslexics on the WRAT Spelling subtest and Reading Quotient scores. In the second study the compensateds differed from the nondyslexics in total raw score and average reading speed on Gray Oral Reading Test. On the other hand, they were different from dyslexics on all reading and spelling variables in both studies, except for PIAT Reading Comprehension in Study 2. Finally, in Study 2, the compensateds were different from both dyslexics and nondyslexics in average reading speed. In conclusion, it appears that compensation does not result from differences in IQ, education, or SES, though it may be influenced to some extent by sex. Compensateds appear very similar to nondyslexics in their reading and spelling skills; however, there appears to be a difference in the automaticity with which they apply these skills.     

Word reading fluency: A transfer appropriate processing account of fluency transfer

Word reading fluency, as indexed by the fast and accurate identification of single words, predicts both general reading ability and reading comprehension. This study compared the effects of context training and isolated word training on subsequent measures of word reading fluency. Good and poor readers were given 12 repetitions of two sets of words; 48 new words were learned in each condition. Words were presented in a story during context training and on a computer screen during isolated word training. Target words were read in isolation at test, randomly displayed within a series containing 72 untrained words. Results show that words trained in isolation are remembered longer and read faster when presented in isolation at test compared to words trained in context. Theoretical implications are discussed in relation to transfer appropriate processing.     

A comprehensive evaluation of lexical reading in Italian developmental dyslexics

Italian developmental dyslexic readers show a striking length effect and have been hypothesised to rely mostly on nonlexical reading. Our experiments tested this hypothesis by assessing whether or not the deficit underlying dyslexia is specific to lexical reading. The effects of lexicality, word frequency and length were investigated in the same group of children in four separate experiments. Although dyslexics were slower and less accurate than skilled readers and had large length effects, they showed lexicality and word frequency effects in both reading aloud and lexical decision. In a cross‐experiment comparison, we show that a single global factor explains a large proportion of the difference in reading performance between dyslexic and skilled readers. This factor may indicate a deficit at a prelexical level of analysis. Lexical activation seemed spared in the dyslexic children based on the effects of lexicality and frequency. These findings contrast the hypothesis that Italian dyslexics primarily engage in nonlexical reading.     

Syllable division: Prerequisite to dyslexics’ literacy

Skill in reading long words is prerequisite to dyslexics’ literacy. Instant recognition of printed symbols is easy for those readers with photographic memories, but dyslexics often fail to recognize visually many long words which are actually familiar to them auditorially. Scientific, automatic, multisensory procedures for dividing longer words into easily read syllables can enable students to translate visual symbols rapidly and thereby to read, write, or spell accurately words of any length. Over one thousand dyslexics, aged seven to fifteen, guided the interdisciplinary team at Texas Scottish Rite Hospital in Dallas to develop, observe results, and test specific structured, sequential steps in working out longer words. The ten-year study (1965–1975) in the Language Laboratory of the Hospital established the Alphabetic Phonics curriculum which is now used successfully, not only in remedial groups but in regular classes of any size or age, in public and private schools in 45 states and six foreign countries. The newly-established Aylett Royall Cox Institute in Dallas prepares teachers and Master Instructors to train both students and other teachers. Comparable Alphabetic Phonics Teacher Training Centers are already established in Houston and Lubbock, Texas, in Oklahoma City, and at Columbia University Teachers College in New York.     

Automaticity training for dyslexics: An experimental study

Less-skilled readers may experience a processing bottleneck in reading comprehension produced by a failure to automate word recognition. The automaticity hypothesis predicts that training which increases rapid and automatic word recognition will improve comprehension. To date few studies have tested this hypothesis. Our goal was to test the automaticity hypothesis by training dyslexic readers (n=35) to access the meaning of words more rapidly. Training consisted of speeded word games implemented on a microcomputer that provided feedback concerning subjects’ speed and accuracy using sound and graphics. Three experimental tasks were administered both before and after training in which trials with trained and untrained stimuli were randomly intermixed. The measures were latency and accuracy of word vocalization, sentence comprehension, and a dual-task procedure designed to measure automaticity. Although pre/post improvement was larger for trained than untrained stimuli, reaction time on the word vocalization and sentence comprehension tasks improved significantly for both trained and untrained stimuli. In contrast, automaticity and sentence comprehension accuracy improved significantly for trained but not untrained stimuli. The training effect in comprehension remained when controlling for increases in word knowledge. The results support the automaticity hypothesis and further suggest that severely disabled readers may benefit from training in automatic word recognition. A portion of this research was supported by a Faculty Development Grant awarded to the first author from Southeastern Louisiana University. Directed by the second author, the Los Angeles study was based on a doctoral dissertation submitted by the first author to the University of Southern California in partial fulfillment of the requirements for the Ph.D. degree. Portions of this work were presented at the meetings of the Society for Research in Child Development, Baltimore, April 1989, and The Orton Dyslexia Society, Portland, November 1991.     

An examination of familial resemblance among subgroups of dyslexics

The goal of the present study was to ascertain whether developmental dyslexics and their affected parents evinced similar patterns of deficits in word recognition skills. Forty dyslexic children and both their biological parents were administered a battery of experimental measures of phonological and orthographic processing. Deficits in component skills were defined in terms of deviations from the performance of normal readers matched on reading achievement level. Four distinct patterns of deficits were found among both the dyslexics and their parents: a subgroup with a specific deficit in processing phonological codes; a subgroup with a specific deficit in processing orthographic codes; a subgroup with deficits in processing both phonological and orthographic codes; and a subgroup of individuals who did not significantly differ from normal readers at the same reading level in either processing domain. Although limited evidence for familial subgroup concordance was obtained in both the phonological and combined phonological subgroups, no concordance was observed among families classified into the orthographic or reading-achievement equivalent subgroups. It was concluded that all affected family members shared a propensity for a phonological deficit, and that some family members share a fundamental problem in processing orthographic information as well. This research was supported by a Biomedical Research Support Grant from the University of Southern California. The research reported in this paper was based on a Ph.D. thesis conducted by the first author at the University of Southern California.     

Coloured filters improve exclusion of perceptual noise in visually symptomatic dyslexics

Previous studies of visually symptomatic dyslexics have found that their contrast thresholds for pattern discrimination are the same as non‐dyslexics. However, when noise is added to the stimuli, contrast thresholds rise markedly in dyslexics compared with non‐dyslexics. This result could be due to impaired noise exclusion in dyslexics. Some dyslexics report a reduction in discomfort experienced while reading and show increased reading speed when using coloured lenses. We hypothesised that coloured lenses work by aiding noise exclusion. Thus the coloured lenses should help performance best under conditions of high visual noise. We measured contrast thresholds for discriminating symbols in the absence and presence of visual noise. The results showed that visually symptomatic dyslexics, who otherwise had elevated contrast thresholds for discriminating symbols in visual noise, had thresholds similar to non‐dyslexics when wearing coloured filters. These findings provide evidence that in visually symptomatic dyslexics coloured filters can improve noise exclusion to normal levels.