Margaret J. Snowling

Developmental Dyslexia and Specific Language Impairment: Same or Different?

Developmental dyslexia and specific language impairment (SLI) were for many years treated as distinct disorders but are now often regarded as different manifestations of the same underlying problem, differing only in severity or developmental stage. The merging of these categories has been motivated by the reconceptualization of dyslexia as a language disorder in which phonological processing is deficient. The authors argue that this focus underestimates the independent influence of semantic and syntactic deficits, which are widespread in SLI and which affect reading comprehension and impair attainment of fluent reading in adolescence. The authors suggest that 2 dimensions of impairment are needed to conceptualize the relationship between these disorders and to capture phenotypic features that are important for identifying neurobiologically and etiologically coherent subgroups.

Phonemes, rimes, vocabulary, and grammatical skills as foundations of early reading development: evidence from a longitudinal study.

The authors present the results of a 2-year longitudinal study of 90 British children beginning at school entry when they were 4 years 9 months old (range = 4 years 2 months to 5 years 2 months). The relationships among early phonological skills, letter knowledge, grammatical skills, and vocabulary knowledge were investigated as predictors of word recognition and reading comprehension. Word recognition skills were consistently predicted by earlier measures of letter knowledge and phoneme sensitivity (but not by vocabulary knowledge, rhyme skills, or grammatical skills). In contrast, reading comprehension was predicted by prior word recognition skills, vocabulary knowledge, and grammatical skills. The results are related to current theories about the role of phonological, grammatical, and vocabulary skills in the development of early reading skills.

Is preschool language impairment a risk factor for dyslexia in adolescence

The literacy skills of 56 school leavers from the Bishop and Edmundson (1987) cohort of preschoolers with specific language impairment (SLI) were assessed at 15 years. The SLI group performed worse on tests of reading, spelling, and reading comprehension than age-matched controls and the literacy outcomes were particularly poor for those with Performance IQ less than 100. The rate of specific reading retardation in the SLI group had increased between the ages of 8 1/2 and 15 years and there had been a substantial drop in reading accuracy, relative to age. However, over 35% had reading skills within the normal range and those who had had isolated impairments of expressive phonology had a particularly good outcome. Our findings highlight the limitations of discrepancy definitions of dyslexia that do not take account of the changing demands of reading over time. We argue that childrens phonological difficulties place them at risk of literacy failure at the outset of reading and that later, impairments of other language skills compromise development to adult levels of fluency.

Phonemic deficits in developmental dyslexia.

SummaryThe present study explored a possible relationship between reading difficulties and speech difficulties. Dyslexic and normal readers, matched for Reading Age, were compared first on a reading task and secondly on a speaking task.In the first experiment, the two groups were asked to read nonsense words aloud. Both groups were able to read one-syllable nonwords equally well but the dyslexics had more difficulty than the normal readers when asked to read two-syllable nonwords. Moreover, they found two-syllable nonwords containing consonant clusters particularly difficult. The probability of their making an error increased with the number of consonant clusters.In the second experiment, the subjects were required to repeat real words and nonsense words of two, three, or four syllables. Both groups found nonsense words more difficult to repeat than real words. However, the relative difficulty of nonsense words over real words was greater for the dyslexic group. Their difficulty was especially marked when they had to repeat four-syllable nonsense words.Thus, in both experiments the dyslexic readers were more affected by the phonological complexity of the stimuli than the normal readers were. Hence, it was suggested that the dyslexic readers tested were subject to a general phonemic deficit which affected their ability to process both written and spoken words.

Family risk of dyslexia is continuous: individual differences in the precursors of reading skill.

The development of 56 children at family risk of dyslexia was followed from the age of 3 years, 9 months to 8 years. In the high-risk group, 66% had reading disabilities at age 8 years compared with 13% in a control group from similar, middle-class backgrounds. However, the family risk of dyslexia was continuous, and high-risk children who did not fulfil criteria for reading impairment at 8 years performed as poorly at age 6 as did high-risk impaired children on tests of grapheme-phoneme knowledge. The findings are interpreted within an interactive model of reading development in which problems in establishing a phonological pathway in dyslexic families may be compensated early by children who have strong language skills.

The Development of Grapheme-Phoneme Correspondence in Normal and Dyslexic Readers.

Abstract The present experiment was concerned with the development of grapheme-phoneme conversion ability in normal and reading-age matched dyslexic readers. The use of grapheme-phoneme correspondences was observed in a recognition memory task for pronounceable nonwords. The nonwords were presented in either the visual or auditory modality and had to be recognized immediately from the converse modality, thus necessitating decoding of stimuli across modalities. The use of grapheme-phoneme correspondences increased with reading age in the normal readers but not in the dyslexics. It was postulated that dyslexics have a specific difficulty in grapheme-phoneme conversion. For them an increase in reading age is attributable mainly to an increase in size of sight vocabulary.

The development of phonological awareness in preschool children

A short-term longitudinal study was carried out on a group of 67 preschool children. At three points in time over a 12-month period, the children were given tests measuring their syllable, rime, and phoneme awareness, speech and language skills, and letter knowledge. In general, childrens rime skills developed earlier than their phoneme skills. Structural equation models showed that articulatory skills and syllable and rime awareness predicted later phoneme awareness.

Developmental differences in sensitivity to semantic relations among good and poor comprehenders: evidence from semantic priming.

Semantic priming for category coordinates (e.g. CAT-DOG; AEROPLANE-TRAIN) and for pairs of words related through function (e.g. BROOM-FLOOR; SHAMPOO-HAIR) was assessed in children with good and poor reading comprehension, matched for decoding skill. Lexical association strength was also manipulated by comparing pairs of words that were highly associated with pairs that shared low association strength. Both groups of children showed priming for function-related words, but for the category co-ordinates, poor comprehenders only showed priming if the category pairs also shared high association strength. Good comprehenders showed priming for category-related targets, irrespective of the degree of prime-target association. These findings are related to models of language development in which category knowledge is gradually abstracted and refined from childrens event-based knowledge and it is concluded that in the absence of explicit co-occurrence, poor comprehenders are less sensitive to abstract semantic relations than normal readers.

Cognitive assessment of dyslexic students in higher education

BACKGROUND Previous studies have shown that the phonological deficits that characterise dyslexia persist into adulthood. There is a growing number of dyslexic students in higher education for whom sensitive diagnostic tests of their reading and reading related difficulties are required. AIMS The main aim of this study was to compare the cognitive skills of dyslexic students with those of their non-dyslexic peers, and to ascertain the impact of cognitive difficulties on their study skills. A second aim was to produce guidelines for the assessment of dyslexia in higher education. SAMPLE The performance of 23 dyslexic students was compared with that of a comparison group of 50 students from the same university who did not report a history of reading difficulty. METHOD Participants completed standardised tests of IQ, reading, spelling and arithmetic and tests tapping phonological processing, verbal fluency and speed of processing. Their performance on a set of study-related tasks including proof reading and précis writing was also assessed and they completed the Brown ADD scales. RESULTS Although dyslexic students did not differ in general cognitive ability from controls, they had deficits in reading and reading related phonological processes. Discriminant function analyses indicated that dyslexia in adulthood can be confirmed with 95% accuracy using only four tests: spelling, nonword reading, digit span and writing speed. CONCLUSIONS The study highlighted the difficulties of dyslexic adults. The persisting difficulties of dyslexic students that affect their study skills need to be recognised by HE institutions so that appropriate support programmes can be put in place.

Ameliorating Children’s Reading-Comprehension Difficulties A Randomized Controlled Trial

Children with specific reading-comprehension difficulties can read accurately, but they have poor comprehension. In a randomized controlled trial, we examined the efficacy of three interventions designed to improve such children’s reading comprehension: text-comprehension (TC) training, oral-language (OL) training, and TC and OL training combined (COM). Children were assessed preintervention, midintervention, postintervention, and at an 11-month follow-up. All intervention groups made significant improvements in reading comprehension relative to an untreated control group. Although these gains were maintained at follow-up in the TC and COM groups, the OL group made greater gains than the other groups did between the end of the intervention and follow-up. The OL and COM groups also demonstrated significant improvements in expressive vocabulary compared with the control group, and this was a mediator of the improved reading comprehension of the OL and COM groups. We conclude that specific reading-comprehension difficulties reflect (at least partly) underlying oral-language weaknesses that can be effectively ameliorated by suitable teaching.