Genetic influences on early word recognition abilities and disabilities: a study of 7-year-old twins
ABSTRACT A fundamental issue for child psychology concerns the origins of individual differences in early reading development.
A measure of word recognition, the Test of Word Reading Efficiency (TOWRE), was administered by telephone to a representative population sample of 3,909 same-sex and opposite-sex pairs of 7-year-old twins. Analyses allowing for sex differences in aetiology were used to estimate the extent to which genetic and environmental influences contribute to normal variation in word recognition and word recognition difficulties, defined by scores below the 5th and 10th percentiles of the unselected sample.
Both normal variation in word recognition and impaired word recognition abilities were substantially heritable (h2 = .65-.67; h(g)2 = .37-.72). Environmental influences were primarily shared between twins, rather than specific to each individual, and small to moderate in magnitude. There was evidence for qualitative sex differences. Quantitative sex differences were also suggested at the extremes, with genetic influences being more important as a cause of reading difficulties in boys than in girls.
These findings indicate that early individual differences and impairments in word recognition are principally influenced by genetic factors and may involve partly distinct genetic or environmental effects in boys and girls. Crucially, they also provide evidence that reading impairments are linked genetically to the normal distribution. Genetic risk for early impairments in word recognition is continuous rather than discrete.
SourceAvailable from: Lorna Gwyneth Hamilton12/2013, Degree: PhD, Supervisor: Prof Maggie Snowling; Dr Emma Hayiou-Thomas
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ABSTRACT: The term "special education" is used, in most cases, for the education of children with learning disabilities, emotional problems, behavioral difficulties, severe physical limitations, or difficulties related to low cognitive abilities. "Gifted education", on the other hand, is used for educating the more able, children with high learning ability or special talents, creative children or children who had achieved highly in school-related or any other area, such as chess, music, painting, etc. However, many gifted children belong to both categories. Some suffer from problems or irregularities unrelated to their giftedness, for example – learning disabilities (e.g. dyslexia, dyscalculia, dysgraphia, ADHD), or physical limitations, such as hearing loss, blindness, or paralysis. Some have to deal with issues directly or indirectly connected to their giftedness. For example: social acceptance has to do with conforming to the classroom norms, speaking about subjects considered age-appropriate, or being careful not to use "high level" vocabulary. A gifted child might find it difficult to participate in activities he or she has no interest in, not expressing feelings or ideas because they might seem odd to the peers, or thinking before using any rare or unconventional word or expression. A gifted child who is bored in the classroom might adopt behaviors such as abstention from activities, daydreaming or becoming the "classroom clown" and disturbing the teachers with voice-making, making jokes at others' expense or even at the teacher's. Such behaviors – not necessary a result of the child's giftedness but related to it – lead, in many cases, to labeling the child as "badly adjusted", "socially misfit", "isolated", or the like. In this article I intend to describe the social and the educational difficulties the gifted child has to deal with in the regular as well as in the gifted classroom and present techniques which might help overcoming them. I will present in detail four, all gifted with either learning disabilities or emotional problems, and the successful interventions they had gone through until reaching reasonable results.
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ABSTRACT: Developmental dyslexia runs in families, and twin studies have confirmed that there is a substantial genetic contribution to poor reading. The way in which discoveries in molecular genetics are reported can be misleading, encouraging us to think that there are specific genes that might be used to screen for disorder. However, dyslexia is not a classic Mendelian disorder that is caused by a mutation in a single gene. Rather, like many other common disorders, it appears to involve combined effects of many genes and environmental factors, each of which has a small influence, possibly supplemented by rare variants that have larger effects but apply to only a minority of cases. Furthermore, to see clearer relationships between genotype and phenotype, we may need to move beyond the clinical category of dyslexia to look at underlying cognitive deficits that may be implicated in other neurodevelopmental disorders. © 2015 The Author(s) Published by the Royal Society. All rights reserved.Proceedings of the Royal Society B: Biological Sciences 05/2015; 282(1806). DOI:10.1098/rspb.2014.3139 · 5.29 Impact Factor