Assessment of the Confidence Calibration Test + new test
Yesterday, I posted a new cognitive test on taketest.xyz, the Confidence Calibration Test. If you want to take the test without biased results, take it now before reading further. You…
Explaining Poland’s fertility paradox
You have probably seen this map: It regularly goes viral on X with the usual abortion debate to follow. The source is this site, where we can also learn that this…
Which countries are best at esports? 2026 update
Given the ease of obtaining scraped datasets with Claude Code, I thought we could update my 2019 study of mental sports with the newest data and better methods. The primary…
Do gun ownership predict homicides taking race into account?
You may have seen a plot like this one: The reader is left to interpret that guns cause homicides. It's correct if we include suicides but it's not true for…
Meta-Analysis of American Race Differences in Intelligence
So our new meta-analysis of the American race gaps in IQ is published! Kirkegaard, E. & Jensen, S. (2025). Meta-Analysis of American Race Differences in Intelligence. Mankind Quarterly, 66(2), 290-300.…
Consequences of racial composition changes in USA 1970-2023
Some years ago, I gave a good idea of a study to a friend, and he did it. But then he just never published his study anywhere, it's just sitting…
Dysgenics for whom?
Some time ago, we published studies showing that the negative correlation between intelligence and fertility varies by other factors. Specifically, we found that it varies by religiousness and conservatism, in…
Motivated reasoning and intelligence
Years ago, a very flashy finding by Kahan and colleagues (2017) got popular (1200+ citations). It goes like this, you give people some matrices of fake study data like these:…
Words can’t bring me down
At least, that's a philosophy of life that some people subscribe to. Others think that words are sort of magic and can hurt you. Even if they are general statements…
New test site: taketest.xyz
Using Claude code I am realizing some projects that were always waiting for a sudden burst of manic energy. These projects now only take some hours of chatting and revising…