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IQ and Personality: What James Heckman Got Wrong
A few years ago James Heckman, together with some other economists, published a study arguing that “achievement tests” and “IQ tests” are different beasts: the former, they claim, are better predictors...
View ArticleGeneral Cognitive Ability Is Almost Perfectly Stable from Early Adulthood to...
Michael Rönnlund and colleagues have a very nice paper out in Intelligence. They show that the individual differences in general intelligence that exist at age 18 are almost perfectly preserved to age...
View ArticleInto the IQ shredder
Wang, M., Fuerst, J., Ren, J. (2016). Evidence of dysgenic fertility in China. Intelligence, 57, 15-24. From the discussion: “We’ve seen, in Table 4, that urban populations in China exhibited a...
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Measurement Error, Regression to the Mean, and Group Differences
Regression to the mean, RTM for short, is a statistical phenomenon which occurs when a variable that is in some sense unreliable or unstable is measured on two different occasions. Another way to put...
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Re-analysis of Willerman’s Study: Race of Mother’s Hypothesis
It’s been almost 50 years now that the famous study of Willerman et al. (1974) has been published. This study is regularly cited as one of the most convincing evidence against the hereditarian...
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Schooling enhances IQ, not intelligence
The idea that schooling raises intelligence still prevails. The influential study review of Ceci (1991) concluded that schooling has a strong impact on IQ scores despite his final warning that observed...
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Fair and Square: A Conclusion on IQ Test Bias
This is a 2-part article. In this first part, the most important studies on internal test bias with respect to racial groups in the item-level, subtest-level and construct-level are reviewed. The...
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DIF Review and Analysis of Racial Bias in Wordsum Test using IRT and LCA
As reviewed in my previous article, the majority of studies on measurement bias, either on the item- or subtest-level, reached an agreement about the fairness of IQ test. Unfortunately, even among...
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Spearman’s g Explains Black-White but not Sex Differences in Cognitive...
In this analysis of the Project Talent data, the g factor model as represented by the Spearman’s Hypothesis (SH) was confirmed for the black-white cognitive difference but not for the sex difference....
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The Structure of Well Designed Online IQ Tests
There are convenient ways researchers can collect IQ scores and correlate the observed scores with measures of self-reported health, socio-economic attainment, personality or political views. In...
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