Early Productive Vocabulary Composition as Precursor of Dyslexia.

PURPOSE: The aim of this study was to gain more insight into the linguistic characterization of dyslexia by investigating vocabulary acquisition. In a previous study, vocabulary at 17 months of age appeared to be related to familial risk (FR) of dyslexia. The aim of this study was to investigate how the differences in lexical composition further develop up to 3 years (35 months) of age and, more importantly, to what extent these differences can be considered specific precursors of dyslexia later on. METHOD: In a total number of 262 children from the Dutch Dyslexia Program, 169 with and 93 without FR for dyslexia, productive vocabulary was assessed with the Dutch version of the MacArthur Communicative Development Inventories at ages 17, 23, 29, and 35 months. Reading tests were administered in Grades 2 and 3, resulting in dyslexia diagnosis in 60 FR children (FR-dys), leaving 109 FR children who developed normal reading skills (FR-nondys) and 93 control children. Children's expressive vocabulary was scored according to the total number of words produced and according to the different major linguistic word categories: nouns, predicates, and closed-class words. The analyses comprised a comparison of total productive vocabulary and the number of words per grammatical category at four different ages for the three groups (FR-dys, FR-nondys, and control). Also, correlations were calculated between vocabulary scores and reading scores. RESULTS: Up to 29 months of age, the total numbers of nouns, predicates, and closed-class words are significantly lower for the FR-dys group as compared with the FR-nondys and control groups; for closed-class words at 23 and 35 months of age, the FR-nondys group's mean values are in between the mean of the FR-dys and control groups. Weak correlations were found between total vocabulary size, number of verbs, number and proportion of predicates at 23 months of age, and word and pseudoword reading fluency in Grades 2 and 3. CONCLUSIONS: These results indicate that development of vocabulary is a significant though weak predictor of reading fluency and dyslexia; vocabulary size and proportion of verbs at 23 months of age, as well as proportion of closed-class words up to 35 months of age, seem to be the most sensitive indicators of delayed vocabulary development and later reading difficulties. There is no indication that FR for dyslexia by itself is related to vocabulary development.

Delayed Early Vocabulary Development in Children at Family Risk of Dyslexia.

Purpose: This study aimed to gain more insight into the relation between vocabulary and reading acquisition by examining early growth trajectories in the vocabulary of children at family risk (FR) of dyslexia longitudinally. Method: The sample included 212 children from the Dutch Dyslexia Program with and without an FR. Parents reported on their children's receptive and expressive vocabulary size at ages 17, 23, 29, and 35 months using the Dutch MacArthur Communicative Development Inventories. Dyslexia status at the end of Grade 2 (8 years) rendered 3 groups: FR-dyslexic (n = 51), FR-nondyslexic (n = 92), and typically developing-nondyslexic (TD) children (n = 69). Results: Repeated measures analyses showed that FR-dyslexic children had lower receptive vocabulary scores from 23 months onward and lower expressive scores from 17 months onward than FR-nondyslexic children. Latent growth curve modeling showed lower initial growth rates in FR-dyslexic children, followed by partial recovery, indicating a delayed increase in receptive and expressive vocabulary. FR-nondyslexic and TD children did not differ. Conclusions: Early deficits in receptive and expressive vocabulary are associated with later reading. Early vocabulary growth of FR-dyslexic children is characterized by a delay but not deviance of growth. Vocabulary can be considered an additional risk factor for dyslexia.

IQ of four-year-olds who go on to develop dyslexia.

Do children who go on to develop dyslexia show normal verbal and nonverbal development before reading onset? According to the aptitude-achievement discrepancy model, dyslexia is defined as a discrepancy between intelligence and reading achievement. One of the underlying assumptions is that the general cognitive development of children who fail to learn to read has been normal. The current study tests this assumption. In addition, we investigated whether possible IQ deficits are uniquely related to later reading or are also related to arithmetic. Four-year-olds (N = 212) with and without familial risk for dyslexia were assessed on 10 IQ subtests. Reading and arithmetic skills were measured 4 years later, at the end of Grade 2. Relative to the controls, the at-risk group without dyslexia had subtle impairments only in the verbal domain, whereas the at-risk group with dyslexia lagged behind across IQ tasks. Nonverbal IQ was associated with both reading and arithmetic, whereas verbal IQ was uniquely related to later reading. The children who went on to develop dyslexia performed relatively poorly in both verbal and nonverbal abilities at age 4, which challenges the discrepancy model. Furthermore, we discuss possible causal and epiphenomenal models explaining the links between early IQ and later reading.

Temporal auditory processing at 17 months of age is associated with preliterate language comprehension and later word reading fluency: an ERP study.

Dyslexia is heritable and associated with auditory processing deficits. We investigate whether temporal auditory processing is compromised in young children at-risk for dyslexia and whether it is associated with later language and reading skills. We recorded EEG from 17 months-old children with or without familial risk for dyslexia to investigate whether their auditory system was able to detect a temporal change in a tone pattern. The children were followed longitudinally and performed an intelligence- and language development test at ages 4 and 4.5 years. Literacy related skills were measured at the beginning of second grade, and word- and pseudo-word reading fluency were measured at the end of second grade. The EEG responses showed that control children could detect the temporal change as indicated by a mismatch response (MMR). The MMR was not observed in at-risk children. Furthermore, the fronto-central MMR amplitude correlated with preliterate language comprehension and with later word reading fluency, but not with phonological awareness. We conclude that temporal auditory processing differentiates young children at risk for dyslexia from controls and is a precursor of preliterate language comprehension and reading fluency.

Differences at 17 months: productive language patterns in infants at familial risk for dyslexia and typically developing infants.

Productive vocabulary composition is investigated in 17-month-old children who are participating in an ongoing longitudinal dyslexia research project in the Netherlands. The project is searching for early precursors for dyslexia and follows a group of children who are genetically at risk for dyslexia and a control group during the first 10 years of their lives. Among other measures, the Dutch version of the MacArthur Communicative Development Inventory: Words and Sentences (N-CDI) is used to investigate early vocabulary development. In this article, the first N-CDI results from the 2 groups of 17-month-old children are compared with each other, with other cross-sectional, cross-linguistic studies, and with a similar Finnish longitudinal dyslexia project. The Dutch children show the same general acquisition pattern as documented for other languages, but there are significant differences between the two groups of 17-month-old children in total number of words produced and in the linguistic composition of their productive vocabulary.