In a forthcoming report in Behavioral Genetics, Professor M. van Leeuwen of VU University (Amsterdam, NL) and colleagues reported that the vast majority of variation in children’s reading performance is heritable, with most of the variance in reading attributable to IQ and memory. The researchers studied twins and siblings (only some of whom had reading disabilities), and they measured children’s reading rate, how many times they could correctly tap blocks in a sequence that had just been displayed, the number times the children could correctly recall the location of a part of a visual display (a catepillar in different holes in an apple), repetition of sequences of digits, and IQ.

Before folks begin using this study to argue that there is a simple causal relationship between IQ and reading, please remember three things: (a) this research also implicates memory as an explanatory factor; (b) there are likely other factors that affect IQ, memory, and reading; and (c) even if lots of variance is explained by such factors as IQ and memory, the remaining variance is sufficient to allow fairly substantial instructional effects.
This study investigates the genetic relationship among reading performance, IQ, verbal and visuospatial working memory (WM) and short-term memory (STM) in a sample of 112, 9-year-old twin pairs and their older siblings. The relationship between reading performance and the other traits was explained by a common genetic factor for reading performance, IQ, WM and STM and a genetic factor that only influenced reading performance and verbal memory. Genetic variation explained 83% of the variation in reading performance; most of this genetic variance was explained by variation in IQ and memory performance. We hypothesize, based on these results, that children with reading problems possibly can be divided into three groups: (1) children low in IQ and with reading problems; (2) children with average IQ but a STM deficit and with reading problems; (3) children with low IQ and STM deficits; this group may experience more reading problems than the other two.
van Leeuwen, M. van den Berg, S. M., Peper, J. S., Hulshoff Pol, H. E., & Boomsma, D. I. (2009). Genetic covariance structure of reading, intelligence and memory in children. Behavioral Genetics, [forthcoming].
Link to the PubMed abstract I’ve reproduced here.
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Famous folks redux
Over on Atlanta Cures Dyslexia Bill Allen has a page headed “Rich and Famous Dyslexics: Dyslexic Talents Unleashed!” that I suspect he hopes will inspire people to work hard and achieve great things.
This is followed by a two overlapping lists of at least 70 names. Most of them are celebrities of one sort or another (entertainment, sports) or historically important figures. People who are familiar with other sites that identify individuals who putatively have Learning Disabilities will recognize many of these names.
There were some new ones for me, though. I do not remember previously reading assertions that Loretta Young, Michael Faraday, Gustave Flaubert, Andrew Jackson, Thomas Jefferson, Steve Jobs, John F. Kennedy, or Robert Kennedy had dyslexia. Does anyone know where I learn about these individuals’ Learning Disabilities?
Sigh. Probably not.
I understand that people hope lists such as this one will prove inspiring to children and even adults who struggle with learning. But, do the lists serve that function? And, are they accurate? Who completed the diagnosis of, for example, Michael Faraday? In addition, what about all the people who definitely have dyslexia and have accomplished a lot, but who are not famous? And what about all the individuals who have dyslexia and are managing to make it without fame and fortune?
Link to Mr. Allen’s page. There’s also a reading program available there; that’s a post for another day.
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