Semen quality and intelligence
Back in the 2000s, there was some interest in semen quality and intelligence: Arden, R., Gottfredson, L. S., Miller, G., & Pierce, A. (2009). Intelligence and semen quality are positively…
Explore psychological correlations at taketest.xyz
Have just finished a neat update to the site. On the correlations page you can now see the matrix of cross-test sample sizes: You can click any of the green…
Race differences in reaction time: data from NHANES 3
Whenever race differences in cognitive ability broadly speaking are brought up, they encounter huge skeptical and emotional opposition. This is understandable, though not grounded in science. One common claim is…
Migrant performance on PISA worldwide
There are some data memes floating around like this one: In German, it shows the performance of Turks on PISA math by year and destination country. It can be seen…
Top universities and national intelligence
We all know that universities differ in quality. But what exactly do we mean by that? How do we determine which are the top universities? There are a number of…
Skin color and intelligence in Latin America
Skin color (lightness or brightness) has been used as a proxy for genetic ancestry for over 100 years. It works alright in many cases. Take this study (Parra et al…
Race, intelligence, and inequality in Brazil
Many years ago I discovered that Brazil publishes the subject level data for many scale testing efforts. These also come with rich surveys concerning the children's homes. The main tests…
Genetic evidence of Ashkenazi intelligence
There are long standing questions about the source of Jewish achievement. Most of this achievement relates to the Ashkenazi subgroup, less so the other Jews. This tells us that the…
Explaining economic growth since 2000
Some days ago I posted some cumulative growth charts for OECD countries, like this one: These results are somewhat affected by the usual GDP issues relating to tax haven (Ireland…
Leftism, mental health, and visual presentation confirmed
So we did another study of leftism, mental health and visual presentation: Hu, M.,& Kirkegaard, E. O. W.(2026). Left-wing ideology, mental health and body modifications. Journal of Open Inquiry in…
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