Lyytinen, H. (2010). Language development, literacy skills and predictive connections to reading in Finnish children with and without familial risk for dyslexia. Journal of Learning Disabilities, 43 (4), 308-321. http://dx

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Children at risk for familial dyslexia (n = 107) and their controls (n = 93) have been followed from birth to school entry in the Jyvaskyla Longitudinal study of Dyslexia (JLD) on developmental factors linked to reading and dyslexia. At the point of school entry, the majority of the at-risk children displayed decoding ability that fell at least 1 SD below the mean of the control group. Measures of speech processing were the earliest indices to show both group differences in infancy and also significant predictive associations with reading acquisition. A number of measures of language, including phonological and morphological skill collected repeatedly from age three, revealed group differences and predictive correlations. Both the group differences and the predictive associations to later language and reading ability strengthened as a function of increasing age. The predictions, however, tend to be stronger and the spectrum of significant correlations wider in the at-risk group. These results are crucial to early identification and intervention of dyslexia in at-risk children.

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The relationship between late-talkers' language development and reading and spelling outcomes was examined in children with and without familial risk for dyslexia. The late-talking subgroups were defined using parent- and test-based assessments of receptive and expressive vocabulary and grammar at 2 and 2.5 years as intake criteria. The language skills of late talkers and the remainders of these two groups were assessed at 3.5, 5, and 5.5 years. Reading/spelling outcomes were compared at the end of the second grade. Late-talking toddlers of the at-risk group who had both poor receptive and expressive skills performed less well than all other groups on language measurements at 5.5 years. In contrast, the control group's late talkers with an expressive delay reached the language level of their age-mates already by 3.5 years, and maintained their age-appropriate position two years later. The most significant differences in the reading skills were found between the at-risk children with receptive and expressive delay and the remainder of the controls. Age-appropriate early language skills did not, however, ensure norm-level fluent reading in the at-risk group. The remainder of the at-risk group performed at a significantly lower level than did the remainder of the controls, both on the oral reading and spelling tasks.

Comparisons of the developmental pathways of the first 5 years of life for children with (N = 107) and without (N = 93) familial risk for dyslexia observed in the Jyväskylä Longitudinal study of Dyslexia are reviewed. The earliest differences between groups were found at the ages of a few days and at 6 months in brain event-related potential responses to speech sounds and in head-turn responses (at 6 months), conditioned to reflect categorical perception of speech stimuli. The development of vocalization and motor behavior, based on parental report of the time of reaching significant milestones, or the growth of vocabulary (using the MacArthur Communicative Development Inventories) failed to reveal differences before age 2. Similarly, no group differences were found in cognitive and language development assessed by the Bayley Scales of Infant Development and the Reynell Developmental Language Scales before age 2.5. The earliest language measure that showed lower scores among the at-risk group was maximum sentence length at age 2. Early gross motor development had higher correlation to later language skills among the at-risk group rather than the control children. The most consistent predictor of differential development between groups was the onset of talking. Children who were identified as late talkers at age 2 were still delayed at the age 3.5 in most features of language-related skills-but only if they belonged to the group at familial risk for dyslexia. Several phonological and naming measures known to correlate with reading from preschool age differentiated the groups consistently from age 3.5. Our findings imply that a marked proportion of children at familial risk for dyslexia follow atypical neurodevelopmental paths. The signs listed previously comprise a pool of candidates for early predictors and precursors of dyslexia, which await validation.

The purposes of this study were to investigate (a) whether children in families with a positive history of dyslexia were more likely to show delays in language development than children without family risk and (b) whether a delayed onset of expressive language (late talking) predicted later language development. We analyzed the language development of 200 children longitudinally at 14, 24, 30, and 42 months and assessed their symbolic play at 14 months. Half of the children (N = 106) were from families with a history of dyslexia (the Dyslexia Risk [DR] group), and other children served as age-matched controls. Parental reports and structured tests were used to assess children's receptive and expressive language and symbolic play. No differences emerged between the two groups in receptive language, symbolic play, or on the Bayley MDI. The groups, however, diverged in expressive language measures. The maximum sentence length at 2 years and object naming and inflectional morphology skills at 3.5 years were higher for the control group than for the DR group. Reynell receptive score at 2.5 years provided the greatest unique contribution to the prediction of the children's receptive and expressive language. Children's risk status did not contribute to receptive language, but provided a significant contribution to their expressive language at 3.5 years, even after the variance associated with parental education and children's previous language skills was controlled. Late talkers in the DR group differed from the other members of the DR group in both receptive and expressive language at 3.5 years, although in the control group children with a late-talking history performed at age-level expectations. The findings suggest that children with a familial risk for dyslexia and with a history of late talking are at higher risk for delays in language acquisition than children without the familial risk for dyslexia.

We review the main findings of the Jyväskylä Longitudinal study of Dyslexia (JLD) which follows the development of children at familial risk for dyslexia (N = 107) and their controls (N = 93). We will illustrate the development of these two groups of children at ages from birth to school entry in the skill domains that have been connected to reading and reading disability in the prior literature. At school entry, the highest score on the decoding task among the poorer half (median) of the at risk children--i.e. of those presumably being most likely genetically affected--is 1 SD below the mean of the control group. Thus, the familial risk for dyslexia shows expected consequences. Among the earliest measures in which group differences as well as significant predictive associations with the first steps in reading have emerged, are indices of speech processing in infancy. Likewise, various measures of early language including pronunciation accuracy, phonological, and morphological skills (but not performance IQ) show both group differences and predictive correlations, the majority of which become stronger as the reliability of the measures increases by age. Predictive relationships tend to be strong in general but higher in the at risk group because of its larger variance in both the predictor variables and in the dependent measures, such as early acquisition of reading. The results are thus promising in increasing our understanding needed for early identification and prevention of dyslexia.