the Lynn effect

the Lynn effect

As frequent visitors know I am a big fan of intelligence -related studies and feel they are most important. If nothing else doing such work is difficult and courageous, because it often flies in the face of political correctness.

Anyway my friend and correspondent Liron pointed out this article: The decline of the world's IQ, by Richard Lynn and John Harvey, and suggests this trend be referred to as the Lynn effect, in counterpoint to the Flynn effect, which is the observation that many human populations have seen an increase in their measured IQ over time. Here's the abstract of the paper:

Dysgenic fertility means that there is a negative correlation between intelligence and number of children. Its presence during the last century has been demonstrated in several countries. We show here that there is dysgenic fertility in the world population quantified by a correlation of − 0.73 between IQ and fertility across nations. It is estimated that the effect of this has been a decline in the world's genotypic IQ of 0.86 IQ points for the years 1950–2000. A further decline of 1.28 IQ points in the world's genotypic IQ is projected for the years 2000–2050. In the period 1950–2000 this decline has been compensated for by a rise in phenotypic intelligence known as the Flynn Effect, but recent studies in four economically developed countries have found that this has now ceased or gone into reverse. It seems probable that this “negative Flynn Effect” will spread to economically developing countries and the whole world will move into a period of declining genotypic and phenotypic intelligence. It is possible that “the new eugenics” of biotechnology may evolve to counteract dysgenic fertility.

The global effect predicted by this paper is somewhat less pronounced than the extrapolations I made in IQ and populations, but are of the same order. I considered differential fertility rates between different countries; this study is more precise, and considers differential fertility rates within countries, based on differential rates between different segments of a population. There is another effect based on generation size which could also be considered, which would directionally reinforce these other two effects.

Interestingly, a Google search for "the decline of the world's IQ" turned up this image as the top hit; it is taken from my now-11-year-old blog post, but was used unattributed in a Sociology 110 class at the University of Hartford. I'm glad I've been able to contribute in small way to the general dialog on this subject :)

I'm delighted to learn that there is a Journal called Intelligence devoted to "research and theoretical studies that contribute to the understanding of Intelligence", and plan to subscribe. (Stay tuned!)