8c%20Three%20Developmental%20Disorders

8c%20Three%20Developmental%20Disorders - Three...

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Unformatted text preview: Three Developmental Three Developmental Disorders Putting it together Primary Reading Primary Reading • Bishop, D. V. M. (2008). Specific language impairment, dyslexia, and autism: Using genetics to unravel their relationship. In C. F. Norbury & J. B. Tomblin & D. V. M. Bishop (Eds.), Understanding developmental language disorders: from theory to practice (pp 67­78). Hove: Psychology Press. Causation (1) Causation (1) • Exogenous Factors – Environmental factors that predict variation in development: • Parental input in tense informativeness, predicts rates of tense and agreement learning in typical children – Hadley, Rispoli, Fitzgerald & Bahnsen (2009) • Socio­economic status and quality of instruction predict improvement in reading – Shaywitz, Mody & Shaywitz (2006). Causation (2) Causation (2) • Endogenous Factors – Genes that lead to differences in neural development • Sex Differences – Boys and girls brains develop at different rates, and we see sex linkage in the prevalence of Autism Behavioral Genetics Behavioral Genetics • The chief way to study genetic effects is by twin study – Monozygotic (MT) twins • 1 zygote splits into two zygotes • Identical twins share all genetic material – Dizygotic (DZ) twins • 2 different zygotes (two simultaneous conceptions) • “Fraternal” twins Heritability Heritability • Heritability or h2 is a statistic: – – It ranges from 0 to 1 It expresses the difference in coincidence of a behavior (in some relevant test score or variable value) between MZ and DZ twins Heritability Heritability • Twins studies of autism, dyslexia and Specific Language Impairment all show significant h2 statistics • But studies also show the influence of shared environment, and unshared environment as well. Multifactorial risk Multifactorial risk • Genes give an individual a propensity, but not necessarily a full blown disorder • The more abilities affected, the more likely a child is to exhibit a disorder – For example if both phonological working memory and grammatical learning are affected, the child is very likely to have Specific Language Impairment Relationships Relationships • Both children with SLI and children with Dyslexia show heritable non­word repetition difficulties – However, children with dyslexia do not exhibit severe grammatical deficits in development • There is very little evidence from twin studies to suggest that Specific Language Impairment and Autism are related disorders Relationships Relationships • There is very little evidence from twin studies to suggest that Specific Language Impairment and Autism are related disorders • Children with Autism have communications deficits, as do children with Specific Language Impairments, but these deficits are probably caused by different mechanisms, as shown by lack of coincidence in twin studies Recap Recap • Twin Studies have been valuable in sorting out endogenous and exogenous influences on language and communications developments • Some forms of Specific Language Impairment may share with Dyslexia a genetic­neurological weakness in phonological processing • Autism involves communications deficits, but they arise from a different mechanism than is found in either Dyslexia or Specific Language Impairment ...
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This note was uploaded on 09/22/2011 for the course SHS 120 taught by Professor Kim,h during the Fall '08 term at University of Illinois, Urbana Champaign.

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