Dimitri van der Linden
|Style over substance|
Dimitri van der Linden is a Dutch psychologist and sexist pseudoscientist who argues females have on average significantly lower IQs than men because they have smaller brains (not withstanding that an "IQ" is a score, not a trait you have). While it is true that women on average have slightly smaller brains than men, there's no evidence this is linked to intelligence (we give more credit to how the brain is wired); furthermore, "It is scientifically well established that there is no difference on average in general intelligence between women and men." For example a number of IQ tests have shown women and men on average, are approximately the same IQ, and any differences are statistically negligible (by <0.5 IQ point).
Unsurprisingly, Linden has struggled to publish his pseudoscience and so was left with the controversial journal Intelligence and the London Conference on Intelligence. Linden et al. 2017 argue against scientific consensus there are no sex differences in intelligence and instead maintain the average IQ of men is 4 points above that of women.
London Conference on Intelligence
The General Factor of Personality (GFP): Its Current Status and its Presumed Relation with Life history Strategy
Speaker: Dimitri van der Linden
It is widely acknowledged that a general factor of intelligence (g) exists in the domain of cognitive abilities. The implications of this general intelligence factor for various life outcomes have now been confirmed in numerous studies (Jensen, 1998; Hernstein & Murray, 1996). In the domain of personality however, the existence of a general factor to date remains a rather controversial topic with many questions yet to be answered. The notion that a general factor of personality (GFP) exists is not new as it was already mentioned by Galton (1887), and after that by several others (e.g., Hofstee, 1993). Yet, systematic research on the GFP started from 2007.
National-level indicators of male hormones (androgen) relate to the global distribution of number of scientific publications and Nobel Prizes
Speaker: Dimitri van der Linden
Co-authors: Edward Dutton, Tri Wicaksono
There are country-level differences in the number of scientific publications produced and the number of science Nobel laureates. Factors such as general development of a country and its average intelligence may partly explain such differences. We hypothesized, however, that male hormones (androgen) may also contribute to scientific activity and the number of science Nobel prizes obtained. At the country level, we tested this hypothesis by examining, on the one hand, the national (per capita) number of citable scientific publications in Scopus and the number of Nobel prizes, and on the other hand, a range of national-level indicators of androgen, namely, 1) the number of CAG-repeats in the AR gene (a gene related to sensitivity for testosterone), 2) androgenic hair, 3) prostate cancer incidence, 4) the D2:D4 finger digit ratio, 5) penile length, and 6) libido (e.g., sex frequency). In addition, we took into account national estimates of IQ and Gross Domestic Product (GDP). Results showed that the vast majority of androgen indicators were either directly related to national-level scientific publications/Nobel prizes, or otherwise showed a relationship with them in those countries in which the average national intelligence was relatively high (e.g., IQ > 90). Even after controlling for GDP, many of the relations between scientific measures and androgen indicators remained intact. Overall, the present findings are the first to directly support the notion that at the national level, once a sufficient level of intelligence is present, androgen may further contribute to scientific activity and the odds of winning a science Nobel Prize.
Sex differences in brain size do translate into difference in general intelligence: Findings from the Human Connectome Study
Speaker: Dimitri van der Linden
Co-author: Curtis S. Dunkel
Characteristics of the brain such as its general size, the density of neurons, and the proportion of gray and white matter have been shown to relate to cognitive abilities. For example, an extensive meta-analysis of Pietschnig et al. (2015) showed that, in the population, the correlation between brain size and general intelligence is around r .24. Studies on brain morphology revealed that gray matter correlated more strongly with general intelligence than white matter (Narr et al., 2007; Posthuma et al., 2002). Sex differences in brain size and morphology have also been shown. Males have bigger brains than females and this difference remains even after controlling for body size. Such findings yielded the question whether there would also be sex differences in intelligence. Although, it was initially believed that males and females did not differ on general intelligence, in 1994 Lynn argued that in adult populations there is indeed a sex differences in intelligence of somewhere around .3 standard deviation, which translates in 3 to 5 IQ points. Moreover, he argued that such findings are related to sex differences in brain size. In a more recent study, Burgaleta et al. (2012) replicated sex differences in brain size, operationalized as the sum of Gray and white matter volumes measures. They found that those differences in brain size were accompanied with sex differences in a limited set of cognitive abilities, such as spatial ability, with males scoring higher. However, they did not find sex differences in general intelligence. Subsequently, they argued that dissimilarities in brain size and morphology (gray and white matter) mainly caused sex differences in specific abilities. Burgaleta et al. acknowledged several limitations in their study such as a limited sample size (N was 100) and the use of undergraduate psychology students as participants. Therefore, in the present study we aimed to test sex differences in brain size and intelligence, using a much large population sample. More specifically, we analyzed the brain imaging findings and cognitive ability tests of the Human Connectome Project (Marcus, et al., 2011; Van Essen, et al., 2013). We used the newly released data that included 900 healthy young adults. In line with the previous study of Burgaleta et al, we operationalized brain size as the sum of all gray and white matter, but in addition we also analysed intracranial volume. General intelligence was operationalized as the first unrotated factor extracted from a range of cognitive ability measures. Analyses of brain size were conducted controlling for height. In the total sample, brain size volume, intracranial volume, and gray and white matter volume showed direct and positive correlations with general intelligence ranging from .16 (white matter) to .26 (intracranial volume). Sex differences in brain size were replicated (F(1, 892) 157.51, η2 .15, p < .0001 and F(1, 892)164.28, η2 .16, p < .0001, for brain size and intracranial volume, respectively). Importantly, we also found a significant sex difference in general intelligence (F(1, 885) 13.42, η2 .02, p < .01). In terms of Cohen’s d, the effect size was .28 which would translate to a difference of approximately 4 IQ points, and is in line with the literature. Based on the findings from this study, we conclude that sex differences in brain size do seem to be accompanied with a difference in general intelligence. As such, the previous findings of Burgaleta et al. (2012) may have likely been due to sample characteristics such as sample size and restriction of range.
- Dimitri van der Linden Erasmus University