IQ, race, age and the Flynn effect

IQby wizardjournal

How the race, intelligence, and genetics question will semi-resolve within the next 10 years
[Via Gene Expression]

Prompted by my post Ta-Nehisi Coates reached out to Neil Risch for clarification on the nature (or lack thereof) of human races. All for the good. The interview is wide ranging, and I recommend you check it out. Read the comments too! Very enlightening (take that however you want).

When it comes to this debate I have focused on the issue of population substructure, or race. The reason is simple. Due to Lewontin’s Fallacy it is widely understood among the “well informed general public” that “biology has disproved race.” Actually, this is a disputable assertion. For a non-crank evolutionary biologist who is willing to defend the race concept for humans, see Jerry Coyne. When you move away from the term “race,” then you obtain even more support from biologists for the proposition that population structure matters. For example, a paper in PLoS GENETICS which came out last week: Analysis of the Genetic Basis of Disease in the Context of Worldwide Human Relationships and Migration. In other words, it is useful to understand the genetic relationships of populations, and individual population identity, because traits correlate with population history. Barring total omniscience population history will always probably matter to some extent, because population history influences suites of traits. If nothing in evolutionary biology makes sense except in light of phylogeny, much of human biology is illuminated by phylogeny.

But that doesn’t speak to the real third rail, intelligence. Very few people are offended by the idea of the correlation between lactase persistence and particular populations. Neil Risch says in the interview with Coates:


While the scientific view is correct, it does seem to focus too much on the effects of genes and not enough on the effects of environment. There may be some genetic effect that we can tease out but I also would not be surprised to see that environmental, especially social,  pressures swamp any genetic effect.

What ever IQ tests measure, it does not appear to be mostly genetic in origin. IQ scores have increased much too rapidly over the last 3-4 generations for there to be a purely genetic reason. In fact, minority ‘races’ today as a group have higher IQs than the majority of people did just a few generations ago. This is not obvious because the IQ of everyone has been increasing.

The Flynn effect  describes the observation that people are getting more ‘intelligent’ as time goes on. People born today are, by these tests, much ‘smarter’ than those born 50 years ago or so. Our grandparents would, by today’s standards, have had IQs around 80.

Adults in 1953 scored almost 17 points less than adults in 2006 in vocabulary parts of IQ tests. The rate of IQ increases about 3 points a decade.

In fact, the reason that older people may appear to have cognitive deficits could actually due, not to any changes in their IQ levels, but simply because of when they were born. Their IQ might not changed at all. It is that simply in comparison to younger adults, they do not appear as smart on IQ tests.

This cannot be due to genetic effects, yet 17 points is more than any ‘racial’ differences. 

Since the Flynn effect occurs in way too short a time for any genetic effects to be primarily responsible, it seems likely that something other than genes is involved in IQ measurements. And the various differences between groups.

Because the same separation seen today between races is also seen between different birth cohorts. No one says that  the difference between old people and young must be due to genetics.  Perhaps no one should say ithe same about racial differences, which are not nearly as great as the differences seen by Flynn.

And this does not get into whether intelligence tests actually measure how smart someone is or whether different types of intelligence may be present and differentially useful. Just a there is likely not one gene responsible for intelligence, there is likely not one type of intelligence that s important for survival. 


5 thoughts on “IQ, race, age and the Flynn effect

  1. The Flynn effect is not correlated with the heritability of a test. Race differences are.

    1. Perhaps but the Flynn effect demonstrates that the non-genetic aspects of the tests are a very significant. Social and other factors may outweigh any purely genetic effect. They are surely much easier for society to ameliorate.

  2. The problem with your reasoning is that highly heritable tests tend to be the most general, the most predictive of success across a variety of other tests – and non-test performance too, such as job and military trainability and academic achievement. These are also the tests that are hardest to improve by environmental effects like nutrition, improved education, cognitive stimulation, or training. Indeed, I have never seen an environmental effect that showed a strong (r > 0.3) correlation with test heritability; genetic effects, such as inbreeding depression, ubiquitously show such strong correlations. So the tests that are least effected by environment are the tests that are most important for predicting success are the tests that show big race differences.

    1. You’re the expert. I am simply trying to discuss the complexity underlying the idea of the tests. Looking only at race, as most people do, attempts to simplify something that is very complex, such as just what ‘g’ is and how it impacts society..That is what I have spent a long time on – how people so often take a complex process and create simplifying heuristics that often fail to accurately capture the complexity. This results in an inability to properly deal with these complex problems.

  3. Nobody is looking “only at race”. I am just making the point that race differences are at least partly intractable and most pronounced on highly important tests. Of course race is not the only important factor in public policy and intelligence. For instance, Jason Richwine’s IQ-based immigration policy would not involve race as an admissions factor independently of IQ.

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