Research Byte: Co-Occurrence and Causality Among #ADHD, #Dyslexia, and #Dyscalculia - #SLD #schoolpsychology #sped #genetics #EDPSY

Co-Occurrence and Causality Among ADHD, Dyslexia, and Dyscalculia

Published in Psychological Science.  Click here to access PDF copy of article

Abstract

ADHD, dyslexia, and dyscalculia often co-occur, and the underlying continuous traits are correlated (ADHD symptoms, reading, spelling, and math skills). This may be explained by trait-to-trait causal effects, shared genetic and environmental factors, or both. We studied a sample of ≤ 19,125 twin children and 2,150 siblings from the Netherlands Twin Register, assessed at ages 7 and 10. Children with a condition, compared to those without that condition, were 2.1 to 3.1 times more likely to have a second condition. Still, most children (77.3%) with ADHD, dyslexia, or dyscalculia had just one condition. Cross-lagged modeling suggested that reading causally influences spelling (β = 0.44). For all other trait combinations, cross-lagged modeling suggested that the trait correlations are attributable to genetic influences common to all traits, rather than causal influences. Thus, ADHD, dyslexia, and dyscalculia seem to co-occur because of correlated genetic risks, rather than causality.

 

Brain timing shares significant genetic component with intelligence

Interesting behavioral genetics study that demonstrates that millisecond temporal processing in the brain has a significant genetic component that is also shared with general intelligence. This (and other) research continues to indicate the importance of investigating "brain timing" as an important component of cognitive functioning. Also, this research indicates that this association is not all genetic--which suggests that interventions that might produce changes in basic neural timing mechanisms may increase cognitive efficiency/functioning.

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SES and IQ: Longitudinal twin study

Yet another study demonstrating the significant relation between SES and intelligence, this time a large longitudinal study of twins. Click on images to enlarge. Prior SES posts can be found here.







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Learning to read related to intellectual development - a longitudinal twins study

Wow...how about the complexity of that large path model?

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Trends In Cognitive Sciences special issue on genetics and cognition

Bilder, R. M., Howe, A., Novak, N., Sabb, F. W., & Parker, D. S. (2011). The genetics of cognitive impairment in schizophrenia: a phenomic perspective. Trends in Cognitive Sciences, 15(9), 428-435.

Geschwind, D. H. (2011). Genetics of autism spectrum disorders. Trends in Cognitive Sciences, 15(9), 409-416.

Harris, S. E., & Deary, I. J. (2011). The genetics of cognitive ability and cognitive ageing in healthy older people. Trends in Cognitive Sciences, 15(9), 388-394.

Hyde, L. W., Bogdan, R., & Hariri, A. R. (2011). Understanding risk for psychopathology through imaging gene-environment interactions. Trends in Cognitive Sciences, 15(9), 417-427.

Loth, E., Carvalho, F., & Schumann, G. (2011). The contribution of imaging genetics to the development of predictive markers for addictions. Trends in Cognitive Sciences, 15(9), 436-446.

Morse, S. J. (2011). Genetics and criminal responsibility. Trends in Cognitive Sciences, 15(9), 378-380.

Munafo, M. R., & Flint, J. (2011). Dissecting the genetic architecture of human personality. Trends in Cognitive Sciences, 15(9), 395-400.

Papassotiropoulos, A., & deQuervain, D. J. F. (2011). Genetics of human episodic memory: dealing with complexity. Trends in Cognitive Sciences, 15(9), 381-387.

Robbins, T. W., & Kousta, S. (2011). Uncovering the genetic underpinnings of cognition. Trends in Cognitive Sciences, 15(9), 375-377.


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Research byte: Intelligence highly heritable and polygenic

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Research byte: Genetics, ADHD, reading difficulties and IQ

The Genetic Association Between ADHD Symptoms and Reading Difficulties: The Role of Inattentiveness and IQ.

Yannis Paloyelis, Fruhling Rijsdijk, Alexis C. Wood, Philip Asherson and , Kuntsi. Journal of Abnormal Child Psychology (2010). 10.1007/s10802-010-9429-7, Published online: 17 June 2010

Abstract

Previous studies have documented the primarily genetic aetiology for the stronger phenotypic covariance between reading disability and ADHD inattention symptoms, compared to hyperactivity-impulsivity symptoms. In this study, we examined to what extent this covariation could be attributed to “generalist genes” shared with general cognitive ability or to “specialist” genes which may specifically underlie processes linking inattention symptoms and reading difficulties. We used multivariate structural equation modeling on IQ, parent and teacher ADHD ratings and parent ratings on reading difficulties from a general population sample of 1312 twins aged 7.9–10.9 years. The covariance between reading difficulties and ADHD inattention symptoms was largely driven by genetic (45%) and child-specific environment (21%) factors not shared with IQ and hyperactivity-impulsivity; only 11% of the covariance was due to genetic effects common with IQ. Aetiological influences shared among all phenotypes explained 47% of the variance in reading difficulties. The current study, using a general population sample, extends previous findings by showing, first, that the shared genetic variability between reading difficulties and ADHD inattention symptoms is largely independent from genes contributing to general cognitive ability and, second, that child-specific environment factors, independent from IQ, also contribute to the covariation between reading difficulties and inattention symptoms.



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Research bytes 7-26-1-: Lots of good intelligence, cognitive, neuro, Big 5, genetic, working memory research stuff

Usual offer -- would you like to read the actual article...in exchange for a brief guest blog post at IQ's Corner?  Contact blogmaster (iap@earthlink.net) if interested.

Ferrer, E., &  McArdle, J. J. (2010). Longitudinal Modeling of Developmental Changes in Psychological Research. Current Directions in Psychological Science, 19(3), 149-154.

In this article we provide a review of recent advances in longitudinal models for multivariate change. We first claim the need for dynamic modeling approaches as a way to evaluate psychological theories. We then describe one such approach, latent change score (LCS) models, and illustrate their utility with a summary of research findings in various areas of psychological science. We then highlight the most prominent features of LCS models. We conclude the article with suggestions for future research on multivariate models of change that can enhance our understanding of psychological science.

Johnson, W. (2010). Understanding the Genetics of Intelligence: Can Height Help? Can Corn Oil? Current Directions in Psychological Science, 19(3), 177-182.

Although the subject is controversial, identifying the specific genes that contribute to general cognitive ability (GCA) has seemed to have good prospects, at least among psychological traits. GCA is reliably and validly measured and strongly heritable, and it shows genetically mediated physiological associations and developmental stability. To date, however, results have been disappointing. Human height shows these measurement characteristics even more strongly than GCA, yet data have indicated that no individual gene has more than trivial effects and this is also true for corn oil. The potential for environmental trigger of genetic expression, long recognized in evolutionary and developmental genetics, as applied to these seemingly disparate traits, can help us to understand the apparent contradiction between the heritability of intelligence and other psychological traits and the difficulty of identifying specific genetic effects.

Lavie, N. (2010). Attention, Distraction, and Cognitive Control Under Load. Current Directions in Psychological Science, 19(3), 143-148.

The extent to which people can focus attention in the face of irrelevant distractions has been shown to critically depend on the level and type of information load involved in their current task. The ability to focus attention improves under task conditions of high perceptual load but deteriorates under conditions of high load on cognitive control processes such as working memory. I review recent research on the effects of load on visual awareness and brain activity, including changing effects over the life span, and I outline the consequences for distraction and inattention in daily life and in clinical populations.

DeYoung, C. G., Hirsh, J. B., Shane, M. S., Papademetris, X., Rajeevan, N., & Gray, J. R. (2010). Testing Predictions From Personality Neuroscience: Brain Structure and the Big Five. Psychological Science, 21(6), 820-828.

We used a new theory of the biological basis of the Big Five personality traits to generate hypotheses about the association of each trait with the volume of different brain regions. Controlling for age, sex, and whole-brain volume, results from structural magnetic resonance imaging of 116 healthy adults supported our hypotheses for four of the five traits: Extraversion, Neuroticism, Agreeableness, and Conscientiousness. Extraversion covaried with volume of medial orbitofrontal cortex, a brain region involved in processing reward information. Neuroticism covaried with volume of brain regions associated with threat, punishment, and negative affect. Agreeableness covaried with volume in regions that process information about the intentions and mental states of other individuals. Conscientiousness covaried with volume in lateral prefrontal cortex, a region involved in planning and the voluntary control of behavior. These findings support our biologically based, explanatory model of the Big Five and demonstrate the potential of personality neuroscience (i.e., the systematic study of individual differences in personality using neuroscience methods) as a discipline

Goldstein, M. H., Waterfall, H. R., Lotem, A., Halpern, J. Y., Schwade, J. A., Onnis, L., & Edelman, S. (2010). General cognitive principles for learning structure in time and space. Trends in Cognitive Sciences, 14(6), 249-258.

An understanding of how the human brain produces cognition ultimately depends on knowledge of large-scale brain organization. Although it has long been assumed that cognitive functions are attributable to the isolated operations of single brain areas, we demonstrate that the weight of evidence has now shifted in support of the view that cognition results from the dynamic interactions of distributed brain areas operating in large-scale networks. We review current research on structural and functional brain organization, and argue that the emerging science of large-scale brain networks provides a coherent framework for understanding of cognition. Critically, this framework allows a principled exploration of how cognitive functions emerge from, and are constrained by, core structural and functional networks of the brain.

Klingberg, T. (2010).  Trainin and plasticity of working memory.  Trends in Cognitive Sciences, 14 (7), 317-324

Working memory (WM) capacity predicts performance in a wide range of cognitive tasks. Although WM capacity has been viewed as a constant trait, recent studies suggest that it can be improved by adaptive and extended training. This training is associated with changes in brain activity in frontal and parietal cortex and basal ganglia, as well as changes in dopamine receptor density. Transfer of the training effects to non-trained WM tasks is consistent with the notion of training-induced plasticity in a common neural network for WM. The observed training effects suggest that WM training could be used as a remediating intervention for individuals for whom low WM capacity is a limiting factor for academic performance or in everyday life.

Technorati Tags: Psychology, school psychology, developmental psychology, educational psychology, forensic psychology, neuropsychology, special education, intelligence, cognitive abilities, cognition, intelligence theories, CHC theory, CHC, Cattell-Horn-Carroll, intelligence, cognition, IQ, IQ tests, Gsm, working memory, attention, cognitive load, Big 5 personality, research bytes, longitudinal research

Race and IQ: Rushton and Jensen review and respond to Richard Nisbett's "Intelligence and How to Get It"

Rushton, J. P., & Jensen, A. R. (2010). Race and IQ: A Theory-Based Review of the Research in Richard Nisbett’s Intelligence and How to Get It. The Open Psychology Journal, 3, 9-35.

Rushton and Jenson's respone to Richard Nisbett's "Intelligence and how to get it" has now been printed and can be accessed by clicking on title link above

Abstract: We provide a detailed review of data from psychology, genetics, and neuroscience in a point-counterpoint format to enable readers to identify the merits and demerits of each side of the debate over whether the culture-only (0% genetic- 100% environmental) or nature + nurture model (50% genetic-50% environmental) best explains mean ethnic group differences in intelligence test scores: Jewish (mean IQ = 113), East Asian (106), White (100), Hispanic (90), South Asian
(87), African American (85), and sub-Saharan African (70). We juxtapose Richard Nisbett’s position, expressed in his book Intelligence and How to Get It, with our own, to examine his thesis that cultural factors alone are sufficient to explain the differences and that the nature + nurture model we have presented over the last 40 years is unnecessary. We review the evidence in 14 topics of contention: (1) data to be explained; (2) malleability of IQ test scores; (3) culture loaded
versus g-loaded tests; (4) stereotype threat, caste, and “X” factors; (5) reaction-time measures; (6) within-race heritability; (7) between-race heritability; (8) sub-Saharan African IQ scores; (9) race differences in brain size; (10) sex differences in brain size; (11) trans-racial adoption studies; (12) racial admixture studies; (13) regression to the mean effects; and (14) human origins research and life-history traits. We conclude that the preponderance of evidence demonstrates that in intelligence, brain size, and other life history traits, East Asians average higher than do Europeans who average higher do South Asians, African Americans, or sub-Saharan Africans. The group differences are between 50 and 80% heritable.

Research Byte 12-23-09: Shared and unshared genetic factors in timed and untimed reading and math abilities

A factorial analysis of timed and untimed measures of mathematics and reading abilities in school aged twins (Sara A. Hart, Stephen A. Petrill and Lee A. Thompson)  Learning and Individual Differences, In Press, Corrected Proof, Available online 27 October 2009,

Abstract

The present study examined the phenotypic and genetic relationship between fluency and non-fluency-based measures of reading and mathematics performance. Participants were drawn from the Western Reserve Reading and Math Project, an ongoing longitudinal twin project of same-sex MZ and DZ twins from Ohio. The present analyses are based on tester-administered measures available from 228 twin pairs (age M = 9.86 years). Measurement models suggested that four factors represent the data, namely Decoding, Fluency, Comprehension, and Math. Subsequent quantitative genetic analyses of these latent factors suggested that a single genetic factor accounted for the covariance among these four latent factors. However, there were also unique genetic effects on Fluency and Math, independent from the common genetic factor. Thus, although there is a significant genetic overlap among different reading and math skills, there may be independent genetic sources of variation related to measures of decoding fluency and mathematics.

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Comments extracted from article

Results suggested a four-factor model including reading Decoding, reading Fluency, reading Comprehension, and Math. Further quantitative genetic analysis suggested that a common genetic factor is important to the covariance among phenotypically distinct latent factors (e.g., Plomin & Kovas, 2005). However, Fluency and Math factors were also influenced by unique genetic influences, independent from the general genetic factor.

Interestingly, the two factors with unique genetic in fluences are the only ones to contain measures of timed performance, or fluency. Previous work has suggested that there are large and significant effects due to heritability on measures of reading fluency (h² = .65–.67; Harlaar, Spinath, Dale, & Plomin, 2005), and mathematics fluency (h² = .63; Hart et al., 2009). It is possible that the fluency components in each of these factors are important for explaining the unique genetic effects on both.

Notably, there is no genetic overlap between the factors which contain fluency-based measures, outside of the general genetic overlap among all the latent factors. That, as well as the comparison of phenotypic models 4 and 5 in Table 3, suggests that the genetic influences of reading fluency are not the same as the genetic influences of mathematics fluency, although both are strongly independently influenced by genes.

It is also interesting to note the shared environmental overlap among all the factors. Instruction in this age-group is typically for the skills represented by these factors (e.g., Chall, 1983). This would serve to influence these processes through the shared environment, especially given that for most students in the early elementary years, academic skill exposure and learning are a function of what is taught in school. Moreover, in the case of twins, they also share the same rearing environment. This overlap is of note as it is shared between all mathematics and reading factors, suggesting that whether it is school- and/or family-level influences, there is a common environmental etiology underlying academic difficulties. This can have ramifications in how academic skill-based interventions are conceptualized.

The math literature sometimes separates math into components of computation and problem solving. Our findings in the current study and others (Petrill & Hart, 2009) suggest that the data were best represented by one latent factor. However, all measures of math are based on the Woodcock–Johnson, which may be serving to make them more similar.

Related to this issue, although the shared environmental influences on math are higher than those on reading, this difference cannot be directly tested statistically.

Authors conclusion

In sum, the results suggest that there are some common genetic and environmental factors that connect reading and mathematics performance. At the same time, there also appear to be independent genetic effects for reading fluency and for mathematics. Although requiring further study, these findings may suggest that the overlap in reading and mathematics performance may be due to both genes and the shared environment whereas the discrepancy between math and reading may be genetically mediated. This has ramifications for our understanding of math and reading difficulties. Independent genetic effects may be serving to make math disability and reading disability distinct, and differentially prevalent. On the other hand, the extent to which they are comorbid in some children, common genes and environments may be affecting the outcomes.

Technorati Tags: psychology, educational psychology, school psychology, cognition, neuropsychology, behavioral genetics, genetics, reading, math, LD, special education, reading fluency, math fluency, Gs, Gq, Grw, intelligence, twin studies

NY Times Op Ed on Evolutionary Psychology: Overstated?

Admission-----I've never done any deep serious reading on evolutionary psychology, although it has played a prominent role in some contemporary intelligence research.  I, like most others, find the explanations interesting and fun to discuss.  I wish I had time to read and study the state-of-the art literature on intelligence and evolutionary psychology. 

Today there was an NY Times Op Ed piece suggesting that EP has been overstated...in reaction to Geoffrey Millers new book "Spent:  Sex, Evolution, and Consumer Behavior."  I've reproduced the text of the Op Ed below (courtesy of my new latest fun toy...my Kindle DX- which I LOVE).  I don't know.  I offer up this Op Ed. as FYI...and hope it generates some comments.  In particular, I'd be interested in readers who are well acquainted with the EP/IQ literature to recommend some readings.  I know David Geary's recent work would be at the top.  Any others?

Enjoy

Human Nature Today (Op Ed; David Brooks), The New York Times (The New York Times Company)
Friday, June 26, 2009, 09:02 AM

Has there ever been a time when there were so many different views of human nature floating around all at once? The economists have their view, in which rational people coolly chase incentives. Traditional Christians have their view, emphasizing original sin, grace and the pilgrim’s progress in a fallen world. And then there are the evolutionary psychologists, who get the most media attention. For 99 percent of human history, they observe, our species lived in small hunter-gatherer bands. The people who survived developed certain mental modules, which have been passed down to us through our genes. Some of these traits serve us well in the modern age. Children have the capacity to learn language with astonishing speed. Some of these traits don’t. Humans have an insatiable craving for fatty and sugary foods. In 2000, Geoffrey Miller, a leading evolutionary psychologist, published a book called “The Mating Mind,” in which he argued that the process of sexual selection among early human groups hardwired many of the behaviors we see in humans today. Some of the traits are physical. Men generally prefer women with a 0.7 waist-to-hip ratio (that’s a 24-inch waist and 36-inch hips, for those of you reading this at the gym). Women generally prefer men who are taller and slightly older. Some of these traits are more subtle. Men, Miller argues, tip better in restaurants, because they’ve been programmed to show how much surplus wealth they have. The average American adult knows 60,000 words, far more than we need. We have all those words because we like to mate with people who caress us with language. Now Miller has published another book, “Spent,” in which he takes evolutionary psychology to the mall. The basic argument is that each of us is born with our own individual level of six big traits: intelligence, openness to new things, conscientiousness, agreeableness, emotional stability and extraversion. These modules are built into humans and other animals (apparently squid can be shy). We are all narcissists, Miller asserts. We spend much of our lives trying to broadcast our excellence in these traits in order to attract mates. Even if we’re not naturally smart or outgoing, we buy products and brands that give the impression we are. According to Miller, driving an Acura, Infiniti, Subaru or Volkswagen is a sign of high intelligence. Driving a Cadillac, Chrysler, Ford or Hummer is a sign of low intelligence. Listening to Bjork is a sign of high intelligence, while listening to Lynyrd Skynyrd is a sign of low intelligence. Watching Quentin Tarantino movies is a sign of high openness. He theorizes that teenage girls may cut themselves as a way to demonstrate their ability to withstand infections. Evolutionary psychology has had a good run. But now there is growing pushback. Sharon Begley has a rollicking, if slightly overdrawn, takedown in the current Newsweek. And “Spent” is a sign that the theory is being used to try to explain more than it can bear. The first problem is that far from being preprogrammed with a series of hardwired mental modules, as the E.P. types assert, our brains are fluid and plastic. We’re learning that evolution can be a more rapid process than we thought. It doesn’t take hundreds of thousands of years to produce genetic alterations. Moreover, we’ve evolved to adapt to diverse environments. Different circumstances can selectively activate different genetic potentials. Individual behavior can vary wildly from one context to another. An arrogant bully on the playground may be meek in math class. People have kaleidoscopic thinking styles and use different cognitive strategies to solve the same sorts of problems. Evolutionary psychology leaves the impression that human nature was carved a hundred thousand years ago, and then history sort of stopped. But human nature adapts to the continual flow of information—adjusting to the ancient information contained in genes and the current information contained in today’s news in a continuous, idiosyncratic blend. The second problem is one evolutionary psychology shares with economics. It’s too individualistic: individuals are born with certain traits, which they seek to maximize in the struggle for survival. But individuals aren’t formed before they enter society. Individuals are created by social interaction. Our identities are formed by the particular rhythms of maternal attunement, by the shared webs of ideas, symbols and actions that vibrate through us second by second. Shopping isn’t merely a way to broadcast permanent, inborn traits. For some people, it’s also an activity of trying things on in the never-ending process of creating and discovering who they are. The allure of evolutionary psychology is that it organizes all behavior into one eternal theory, impervious to the serendipity of time and place. But there’s no escaping context. That’s worth remembering next time somebody tells you we are hardwired to do this or that.

Technorati Tags: psychology, educational psychology, learning, school psychology, neuropsychology, evolution, evolutionary psychology, Geoffrey Miller, David Geary, NY Times, David Brooks

Genetics and high cognitive ability: Behavior Genetics special issue

The most recent issue of Behavior Genetics is devoted to exploring the relations between genetics and high cognitive abilities.  The guest editors are Plomin and Haworth

• R. Plomin & C Haworth, (2009). INTRODUCTION: Genetics of High Cognitive Abilities.  INTRODUCTION: Genetics of High Cognitive Abilities.  Behavior Genetics, 39, 347–349

In their introduction to the special issue, the editors state that this is the "first-ever collection of papers focused on the genetics of high cognitive abilities."  The focus of the issue is to explore the hypothesis that the  etiology of high cognitive ability differs from the etiology of the normal distribution of cognitive ability (aka., Discontinuity Hypothesis; Petrill et al. 2009).

As stated in the intro, "three of the papers focus on general cognitive ability (g), two on reading, one on mathematics, one on a diverse set of intellectual, creative and sports abilities, and one is a multivariate genetic analysis of g, reading, mathematics and language."

Of particular interest is the article by Haworth et al. (2009b) as it "presents a mega-analysis of high g for 11,000 twin pairs across six studies from these four countries. This first adequately powered study of high g (top 15%) finds substantial genetic influence (heritability of 0.50 with a 95% confidence interval of 0.41–0.60) and moderate shared environmental influence (0.28, 0.19–0.37). These estimates are not significantly different from parameter estimates for the entire distribution."  The article by Petrill et al., 2009) presents similar findings from their study that investigated high math performance.   According to the editors reading of Petrill et al., "genetic and shared environmental estimates for high (top 15%) math ability were not significantly different from those obtained across the normal range of ability."   Further support for the Continuity Hypothesis were similar findings  by Vinkhuyzen et al. (2009) in their article "Heritability estimates for Music, Arts, Writing, Language, Chess, Mathematics, Sports, Memory and Knowledge."  Collectively these different studies are consistent with the Continuity Hypothesis (and not the Discontinuity Hypothesis), which is the view that "high cognitive ability is the quantitative extreme of the same genetic and environmental influences responsible for variation throughout the normal distribution."

Other papers in this special issue report on investigations re: how genes and environment interact developmentally.  As summarized by the guest editors:

• Brant et al. (2009) show that shared environment decreases from infancy to adolescence, heritability increases, and genes largely account for age-to-age stability.
• Kirkpatrick et al. ( 2009) confirm in a study of adolescent twins that high cognitive ability shows significant shared environmental influence and then use the power of the adoption design to ask the extent to which parental education and occupation and disruptive life events can account for this shared environmental influence.
• Friend et al. ( 2009) report an interesting genotype– environment interaction between high reading ability and parental education: The heritability of high reading ability was higher for twins when parents were less well educated, which the authors interpret as indicating a genetic effect on resilience in the face of environmental disadvantage.
• Finally, a paper by Haworth et al. ( 2009a) for the first time tests the generalist genes hypothesis for high ability. A multivariate genetic analysis of general cognitive ability, reading, mathematics and language performance for the top 15% of the distribution yields genetic correlations just as high among these diverse cognitive abilities as has been found in unselected samples.

Rushton and Jensen's response to Nisbett's "Intelligence and how to get it"

Yesterday I made an FYI post re: an op-ed piece in the NY Times (Rising Above IQ) regarding Richard Nisbett's book on race, culture, schooling and IQ. To say the least, Nisbett's publication has generated considerable response and criticism from intelligence scholars. Thanks to a comment posted to this blog, I was made aware of one of these scholarly responses at Philppe Rushton's web page. He, together with Aruthur Jensen, have a "working paper" in progress and welcome comments on the current draft. A copy can be found by clicking here. Below is the abstract.

Let the games begin.

Rushton, P. & Jensen, A. Race and IQ: A Theory-Based Review of the Research in Richard Nisbett’s Intelligence and How to Get It. Manuscript in preparation.

Abstract

We provide a detailed review of data from psychology, genetics, and neuroscience in a point-counterpoint format to enable readers to identify the merits and demerits of each side of the debate over whether the culture-only (0% genetic-100% environmental) or hereditarian (50% genetic-50% environmental) model best explains observed mean ethnic group differences in intelligence test scores: Jewish (mean IQ = 113), East Asian (106), White (100), Hispanic (90), South Asian (87), African American (85), and sub-Saharan African (70). We juxtapose Richard Nisbett’s position, expressed in his book Intelligence and How to Get It, with our own, to examine his thesis that cultural factors alone are sufficient to explain the differences and that the hereditarian model we have presented over the last 40 years is unnecessary. We review the evidence in 14 topics of contention: (1) data to be explained; (2) malleability of IQ test scores; (3) culture-loaded versus g-loaded tests; (4) stereotype threat, caste, and “X” factors; (5) reaction-time measures; (6) within-race heritability; (7) between-race heritability; (8) sub-Saharan African IQ scores; (9) race differences in brain size; (10) sex differences in brain size; (11) trans-racial adoption studies; (12) racial admixture studies; (13) regression to the mean effects; and (14) human origins research and life-history traits. We conclude that the preponderance of evidence demonstrates that in intelligence, brain size, and other life history traits, East Asians average higher than do Europeans who average higher do South Asians, African Americans, or sub-Saharan Africans. The group differences are between 50 and 80% heritable.

Technorati Tags: psychology, school psychology, educational psychology, cognition, intelligence, IQ, IQ tests, IQ scores, genetics, heredity, race, Nisbett, IQs Corner, ISIR

More on rapid naming (RAN, phonemic awareness (PA) and reading: Genetic evidence

The importance of RAN (rapid automatic naming) and PA (phonemic awareness) for reading (and Dx of dyslexia) has been blogged and logged at this blog previously.

Toady I skimmed a nice bit of behavioral genetic research (Naples et al., 2009) in the journal Biological Psychology that reports on the unique and shared genetic variance of the constructs/traits of RAN and PA. Although a lengthy, and at times, complex article, the bottom line is that behavioral genetic evidence suggests that RAN (placed under Glr in CHC taxonomy) and PA (under Ga in CHC taxonomy) are different constructs, although they do have some shared genetic variance.

As articulated by the late John Horn, evidence for differences in constructs comes from multiple sources--structural (factor analytic), behavioral genetic, developmental, criterion-outcome, and neurocognitive. This study provides construct validity evidence in the form of behavioral genetic evidence.

This work’s objective was to offer additional insights into the psychological and genetic bases of reading ability and disability, and to evaluate the plausibility of a variety of psychological models of reading involving phonological awareness (PA) and rapid naming (RN), both hypothesized to be principal components in such models. In Study 1, 488 unselected families were assessed with measures of PA and RN to investigate familial aggregation and to obtain estimates of both the number and effect-magnitude of genetic loci involved in these traits’ transmission. The results of the analyses from Study 1 indicated the presence of genetic effects in the etiology of individual differences for PA and RN and pointed to both the shared and unique sources of this genetic variance,which appeared to be exerted by multiple (3–6 for PA and 3–5 for RN) genes. These results were used in Study 2 to parameterize a simulation of 3000 families with quantitatively distributed PA and RN, so that the robustness and generalizability of the Study 1 findings could be evaluated. The findings of both studies were interpreted according to established theories of reading and our own understanding of the etiology of complex developmental disorders.

Technorati Tags: psychology, school psychology, educational psychology, neuropsychology, cognition, intelligence, education, special education, reading, dyslexia, LD, learning disabilities, SLD, genetics, behavioral genetics, rapid naming, phonemic awareness, RAN, PA, CHC theory

NYTimes book review: Get Smart

From The New York Times:

Get Smart
By JIM HOLT

A prominent cognitive psychologist stresses the nonhereditary factors
in determining I.Q....

http://www.nytimes.com/2009/03/29/books/review/Holt-t.html

Get The New York Times on your iPhone for free by visiting http://nytimes.com/iphoneinstaller

Kevin McGrew PhD
Educational/School Psych.
IAP (www.iapsych.com)

Sent from KMcGrew iPhone (IQMobile). (If message includes an image-
double click on it to make larger-if hard to see)

Random tidbits from mind blogosphere 5-13-08

• Are executive functions highly genetic? Check out post at Developing Intelligence for comments on a recent research study.
• Sharp Brains continues to impress above all the rest in documenting and explaining the brain fitness movement. Now they are offering a Brain Fitness Webinar Series. Kudos to SB.
• Self-serving blog plug. Check out post regarding recent genetic research suggestive of a link between autism and mental timing (the IQ Brain Clock)
  

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, neuroscience, intelligence, cognition, executive function, brain fitness, autism, mental timing, IQ Brain Clock

Genetics study links autism and brain clock

I just made a post re: interesting recent genetic research suggesting a link between Autism and mental timing (the IQ Brain Clock) at my other blog--The IQ Brain Clock.

Born to count?

Interesting post at Deric Bownds Mindblog re: article suggesting we have an innate number sense.

Technorati Tags: psychology, educational psychology, school psychology, education, math, arithmetic, number sense, genetics, Gq, IQs Corner, Mindblog

DNA deletion linked to Autism

A news report of a new study, in the prestigious New England Journal of Medicine, suggesting a genetic link between a DNA deletion and autism.

Technorati Tags: autism, austic, intelligence, genetics, developmental disorders, educational psychology, school psychology, neuroscience, neuropsycology, special education

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More on IQ and heritability

Bob Williams has made me aware of some of his recent thoughts on the IQ-Heritability research. His document can be viewed/downloaded at the following link. Chris Brand, at IQ & PC, provides some comments on Bob's work (you will need to scroll down a bit on today's posts by Dr. Brand)

Technorati Tags: psychology, educational psychology, school psychology, neuropsychology, clinical psychology, intelligence, IQ, IQ tests, IQ scores, genetics, heritability, g, g-factor

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