Lack of replication for the myosin-18B association with mathematical ability in independent cohorts.

Twin studies indicate that dyscalculia (or mathematical disability) is caused partly by a genetic component, which is yet to be understood at the molecular level. Recently, a coding variant (rs133885) in the myosin-18B gene was shown to be associated with mathematical abilities with a specific effect among children with dyslexia. This association represents one of the most significant genetic associations reported to date for mathematical abilities and the only one reaching genome-wide statistical significance. We conducted a replication study in different cohorts to assess the effect of rs133885 maths-related measures. The study was conducted primarily using the Avon Longitudinal Study of Parents and Children (ALSPAC), (N = 3819). We tested additional cohorts including the York Cohort, the Specific Language Impairment Consortium (SLIC) cohort and the Raine Cohort, and stratified them for a definition of dyslexia whenever possible. We did not observe any associations between rs133885 in myosin-18B and mathematical abilities among individuals with dyslexia or in the general population. Our results suggest that the myosin-18B variant is unlikely to be a main factor contributing to mathematical abilities.

Accessing and selecting word meaning in autism spectrum disorder.

BACKGROUND: Comprehension difficulties are commonly reported in autism spectrum disorder (ASD) but the causes of these difficulties are poorly understood. This study investigates how children with ASD access and select meanings of ambiguous words to test four hypotheses regarding the nature of their comprehension difficulties: semantic deficit, weak central coherence, reduced top-down control and inhibition deficit. METHODS: The cross-modal semantic priming paradigm was used. Children heard homonym primes in isolation or as final words in sentences biased towards the subordinate meaning and then named picture targets depicting dominant or subordinate associates of homonyms. RESULTS: When homonyms were presented in isolation, children with ASD and controls showed priming for dominant and subordinate pictures at 250ms ISI. At 1,000ms ISI, the controls showed dominant (but not subordinate) priming whilst the ASD group did not show any priming. When homonyms were presented in subordinate sentence contexts, both groups only showed priming for context-appropriate (subordinate) meanings at 250ms ISI, suggesting that context has an early influence on meaning selection. At 1,000ms ISI the controls showed context-appropriate (but not inappropriate) priming whereas the ASD group showed both appropriate and inappropriate priming. CONCLUSIONS: Children with ASD showed intact access to semantic information early in the time course of processing; however, they showed impairments in the selection of semantic representations later in processing. These findings suggest that a difficulty with initiating top-down strategies to modulate online semantic processing may compromise language comprehension in ASD. Implications for intervention are discussed.

The relationship between paired associate learning and phonological skills in normally developing readers.

Seventy-five 6- to 11-year-old children were administered tests of phonological awareness, verbal short term memory (STM), and visual-verbal paired associate learning (PA learning) to investigate their relationship with word recognition and decoding skills. Phonological awareness was a stronger concurrent predictor of word recognition than verbal STM, and phonological awareness but not verbal STM was a predictor of learning in the PA learning task. Importantly, measures of phonological awareness and PA learning both accounted for independent variance in word reading, even when decoding skill was controlled. The results suggest that PA learning and phonological awareness tasks tap two separate mechanisms involved in learning to read. The results are discussed in relation to current theories of reading development.

Rapid auditory processing and phonological ability in normal readers and readers with dyslexia.

According to a prominent theory, the phonological difficulties in dyslexia are caused by an underlying general impairment in the ability to process sequences of rapidly presented, brief sounds. Two studies examined this theory by exploring the relationships between rapid auditory processing and phonological processing in a sample of 82 normally reading children (Study 1) and by comparing 17 children with dyslexia to chronological-age and reading-age control participants on these tasks (Study 2). In the normal readers, moderate correlations were found between the measure of rapid auditory processing (Auditory Repetition Task, or ART) and phonological ability. On the ART, the dyslexia group performed at a level similar to that of the reading-age control group but obtained scores that were significantly below those of the chronological-age control group. This difference was due to a subgroup of 4 children in the dyslexia group who had particular difficulty with the ART. The phonological skills of these individuals were not worse than those of the children in the dyslexia group who were unimpaired on the ART. The discussion argues that there is no evidence that phonoogical difficulties are secondary to impairments of rapid auditory processing, as measured by the ART, and highlights the need to examine the strategic and cognitive demands involved in tasks of rapid auditory processing.

Educational attainments of school leavers with a preschool history of speech-language impairments.

This paper reports a follow-up study of a cohort of 16- and 17-year-olds with a preschool history of speech-language impairment and whom Bishop and Edmundson (1987) originally studied. Information collected by questionnaire showed that the GCSE grades of those whose language impairments had resolved by 5;06 were below those of age-matched controls. However, the number of GCSE examinations entered and passed was significantly more than those of the 'persistent S-LI' and 'general delay' groups. Overall, IQ was the strongest predictor of educational attainment. However, even when IQ was controlled, literacy skills accounted for independent variance in achievement, especially among those with a history of language difficulty. The survey also noted that the majority of students across all groups remained in full-time education; however, the adolescents with a background of S-LI were more likely to follow vocational and employment training courses rather than A-levels.

From language to reading and dyslexia.

This paper reviews evidence in support of the phonological deficit hypothesis of dyslexia. Findings from two experimental studies suggest that the phonological deficits of dyslexic children and adults cannot be explained in terms of impairments in low-level auditory mechanisms, but reflect higher-level language weaknesses. A study of individual differences in the pattern of reading skills in dyslexic children rejects the notion of 'sub-types'. Instead, the findings suggest that the variation seen in reading processes can be accounted for by differences in the severity of individual children's phonological deficits, modified by compensatory factors including visual memory, perceptual speed and print exposure. Children at genetic risk who go on to be dyslexic come to the task of reading with poorly specified phonological representations in the context of a more general delay in oral language development. Their prognosis (and that of their unaffected siblings) depends upon the balance of strengths and difficulties they show, with better language skills being a protective factor. Taken together, these findings suggest that current challenges to the phonological deficit theory can be met.

Precursors of literacy delay among children at genetic risk of dyslexia.

This paper reports the literacy skills of 63 children selected as being at genetic risk of dyslexia compared with 34 children from families reporting no history of reading impairment. Fifty-seven per cent of the at-risk group were delayed in literacy development at 6 years compared with only 12% of controls. The "unimpaired" at-risk group were not statistically different from controls on most cognitive and language measures at 45 months, whereas the literacy-delayed group showed significantly slower speech and language development, although they did not differ from controls in nonverbal ability. Letter knowledge at 45 months was the strongest predictor of literacy level at 6 years. In addition, early speech and language skills predicted individual differences in literacy outcome and genetic risk accounted for unique variance over and above these other factors. The results are discussed in terms of an interactive developmental model in which semantic and phonological skills support early reading acquisition.

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.

Working memory deficits in poor comprehenders reflect underlying language impairments.

Three experiments assessed memory skills in good and poor comprehenders, matched for decoding skill. Experiments 1 and 2 investigated phonological and semantic contributions to short-term memory by comparing serial recall for words varying in length, lexicality, and concreteness. Poor comprehenders showed normal sensitivity to phonological manipulations (length and lexicality) but, consistent with their semantic weaknesses, their recall of abstract words was poor. Experiment 3 investigated verbal and spatial working memory. While poor comprehenders achieved normal spatial spans, their verbal spans were impaired. These results are discussed within a theoretical framework in which the memory difficulties associated with poor reading comprehension are specific to the verbal domain and are a concomitant of language impairment, rather than a cause of reading comprehension failure.

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 children's 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.

Problems of behaviour, reading and arithmetic: assessments of comorbidity using the Strengths and Difficulties Questionnaire.

BACKGROUND: Estimates of academic underachievement among school children vary widely, depending on the geographical location and on the criteria used to define attainment. AIM: To examine the relationship between behaviour problems and academic attainment in a large UK primary school. METHOD: A school population (364 children from Years 3 to 6 inclusive) were assessed on a range of cognitive ability tasks. These included standardised tests of reading, arithmetic and verbal and non-verbal intelligence. Under-achievement was assessed using different criteria. To assess behaviour, teachers completed the Strengths and Difficulties Questionnaire (Goodman, 1997) for each participating child. Finally, academic progress of a subset of children was assessed after one year. RESULTS: Indicated a significant relationship between behaviour and academic attainment; prosocial behaviour was positively correlated with reading and arithmetic, hyperactivity and conduct problems were negatively correlated. This association was especially strong in the children rated by the questionnaire as hyperactive, where around 1 in 5 had a specific reading deficit. However, there was no evidence to indicate that children with behaviour problems made less academic progress over a one-year period relative to their peers. CONCLUSION: The study highlights the importance of assessing both cognitive skills and behaviour, particularly when planning the educational management of children with reading difficulties.

Individual differences in contextual facilitation: evidence from dyslexia and poor reading comprehension.

Ninety-two 7- to 10-year-old children read words presented in isolation or following a spoken sentence context. In absolute terms, poor readers showed more contextual facilitation than good readers. However, when the relative benefit of context was assessed, this was greater for children with better reading skills, and comprehension was a better predictor of contextual facilitation than decoding. Study 2 compared the performance of dyslexics with that of reading-age matched poor comprehenders and normal readers. The dyslexics showed greater contextual facilitation than the normal readers who, in turn, showed more priming than poor comprehenders. The results show that dyslexic children use context to compensate for poor decoding skills, whereas children with poor reading comprehension skills fail to benefit from context as much as normal readers.

Language-impaired preschoolers: a follow-up into adolescence.

This paper reports a longitudinal follow-up of 71 adolescents with a preschool history of speech-language impairment, originally studied by Bishop and Edmundson (1987). These children had been subdivided at 4 years into those with nonverbal IQ 2 SD below the mean (General Delay group), and those with normal nonverbal intelligence (SLI group). At age 5;6 the SLI group was subdivided into those whose language problems had resolved, and those with persistent SLI. The General Delay group was also followed up. At age 15-16 years, these children were compared with age-matched normal-language controls on a battery of tests of spoken language and literacy skills. Children whose language problems had resolved did not differ from controls on tests of vocabulary and language comprehension skills. However, they performed significantly less well on tests of phonological processing and literacy skill. Children who still had significant language difficulties at 5;6 had significant impairments in all aspects of spoken and written language functioning, as did children classified as having a general delay. These children fell further and further behind their peer group in vocabulary growth over time.

The effects of phonetic similarity and list length on children's sound categorization performance.

Three experiments investigating children's performance on tests of sound categorization are reported. In two experiments, the children had to decide which was the "odd one out" in a sequence of three, four, and five words. In each case the "oddity" judgement required selecting the word which differed in its final consonant, producing a different rime segment. The odd word differed either by one phonetic feature (voice or place) or by both voice and place, from the others in the sequence. Oddity judgements were easier when the odd word was phonetically dissimilar to the background items but, contrary to expectation, performance did not decline as list length increased. Experiment 3 extended these findings by showing that place-only changes were more difficult than voice-only changes. Sound categorization performance correlated with memory span for words, but memory span did not make an independent contribution to sound categorization once age and reading skills had been controlled. The experiments show that the sound categorization task taps individual differences in speech perception mechanisms but that memory load is less crucial to this task than has often been supposed.