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: Elsje van Bergen
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- "Some twin studies report evidence for shared-environmental influences (reading disability e.g. Friend, Defries, & Olson, 2008; Harlaar et al., 2005; reading ability e.g. Petrill et al., 2007; Taylor & Schatschneider, 2010). "
ABSTRACT: Reading is the processing of written language. Family resemblance for reading (dis)ability might be due to transmission of a genetic liability or due to family environment, including cultural transmission from parents to offspring. Familial-risk studies exploring neurobehavioral precursors for dyslexia and twin studies can only speak to some of these issues, but a combined twin-family study can resolve the nature of the transmitted risk. Word-reading fluency scores of 1100 participants from 431 families (with twins, siblings and their parents) were analyzed to estimate genetic and environmental sources of variance, and to test the presence of assortative mating and cultural transmission. Results show that variation in reading ability is mainly caused by additive and non-additive genetic factors (64%). The substantial assortative mating (rfather-mother=0.38) has scientific and clinical implications. We conclude that parents and offspring tend to resemble each other for genetic reasons, and not due to cultural transmission. Copyright © 2015 Elsevier Inc. All rights reserved.Brain and Language 08/2015; DOI:10.1016/j.bandl.2015.07.008 · 3.22 Impact Factor
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- "I first met his parents who wanted to know more about dyslexia – the diagnosis he received after he was referred to a full psychodiagnosis evaluation. This evaluation revealed an unconceivable gap between the expected achievements from such a quick, easy to handle, diligent and good-natured boy, as he was 1 The subject will be referred to as " he " because in all dyslexia studies the male/female rate found had been from 2:1 to 15:1 (Finucci et al., 1981; Harlaar et al., 2005; Hawke et al., 2007, 2009; Miles et al., 1998; Shaywitz et al., 1990; Stevenson, 1990 Vogel, 1990) "
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.04/2015; 3(3):28-45. DOI:10.18052/www.scipress.com/ILSHS.51.19
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- "Twin studies provide evidence for the importance of genetic influences for the genesis of reading problems, as well as for normal variations in reading skills in the population . It has been suggested that as much as 70% of the variation in 7-year-olds’ decoding skills is attributable to genetic differences . Similarly, normal variations in oral language skills are heritable, and there is evidence for the importance of genetic influences in the aetiology of specific language impairment [51,52]. "
ABSTRACT: We review current knowledge about reading development and the origins of difficulties in learning to read. We distinguish between the processes involved in learning to decode print, and the processes involved in reading for meaning (reading comprehension). At a cognitive level, difficulties in learning to read appear to be predominantly caused by deficits in underlying oral language skills. The development of decoding skills appears to depend critically upon phonological language skills, and variations in phoneme awareness, letter-sound knowledge and rapid automatized naming each appear to be causally related to problems in learning to read. Reading comprehension difficulties in contrast appear to be critically dependent on a range of oral language comprehension skills (including vocabulary knowledge and grammatical, morphological and pragmatic skills).Philosophical Transactions of The Royal Society B Biological Sciences 01/2014; 369(1634):20120395. DOI:10.1098/rstb.2012.0395 · 7.06 Impact Factor