Inductivist

Centrists like Richard Hanania go on endlessly about how dumb MAGA is compared to Democrats. These types are flat wrong, but everyone assumes they're right based on data showing lower IQs for conservatives. Here are the mean IQ scores for those who voted for Trump vs. Hillary. The mean is slightly higher for Trump voters. At least get your facts straight before mocking people.  

Some researchers have claimed that the average IQ of the Irish used to be really low by West European standards but has recently caught up, and this shows that IQ can be raised by improving social conditions. 

Russell Warne recently conducted an analysis of 55 samples of 29k Irish examinees, the IQ data collected in various years from 1916 to 2015. The mean was found to be 98.0. As you see in his graph below, there was at most a slight increase in mean IQ over this period. This pattern contradicts the optimistic nurturist view. 

A reality-check approach might offer a nice complement to the IQ data. If mean Irish IQ were, say, 85 a century ago, we should not expect Ireland to have produced many eminent scientists. 

I will rely on the inventories of significant scientists, mathematicians, and technologists listed in Charles Murray's Human Accomplishment. I will use Scotland, Denmark, Norway, and Finland as comparisons. They are NW European countries with population sizes roughly similar to that of Ireland, and as far as I know, no one has claimed that those countries used to be low-IQ. 

You can see from the lists below that Scotland smokes the other countries with 57 significant figures. Pound for pound, Scotland is an impressive country. Denmark is a distant second with 14 eminent men, but Ireland is a close third with 13 significant figures. Norway has 8, and poor Finland only has one. Impressive country but not for its past scientists. 

So Ireland falls to the middle of the pack. No reason here to think that the Irish used to be dumb but have only recently improved their intelligence level.  

Scotland -- 57 Significant Figures

Astronomy
Thomas Henderson

Biology
Robert Brown
John Haldane
John McCleod

Chemistry
Archibald Couper
John Cranston
William Cullen
James Dewar
Alexander Fleck
Thomas Graham
Charles Macintosh
William Ramsay
Daniel Rutherford
James Swinburne
James Waterston
James Young

Earth Sciences
James Ewing
James Hall
James Hutton
Charles Lyell
William Maclure
Roderick Murchison
William Nicol
Charles Thomson

Physics
David Brewster
James Maxwell
William Thomson
Charles Wilson

Math
James Gregory
Colin Maclaurin
John Napier
James Stirling
Joseph Wedderburn

Medicine
Charles Bell
Alexander Fleming
John Hunter
James Lind
Patrick Manson
Edward Mellanby
John Pringle
James Simpson
Robert Whytt

Technology
John Baird
Alexander Ball
Patrick Bell
James Dewar
Kirkpatrick Macmillan
John McAdams
Andrew Meikle
William Murdock
James Nasmyth
William Rankine
James Thomson
William Thomson
Robert Watson-Watt
James Watt
James Young 

Denmark -- 14 Significant Figures

Astronomy
Tycho Brahe
John Dryer
Ejnar Hertzsprung
Ole Romer

Biology
Peter Dam
Johan Fabricius
Hans Gram
Wilhelm Johannsen

Chemistry
Soren Sorensen

Earth Sciences
0

Physics
Erasmus Batholin
Niels Bohr
Hans Orsted

Math
0

Medicine
Niels Finsen

Technology
Valdemar Poulsen

Norway -- 8 Significant Figures

Astronomy
0

Biology
0

Chemistry
Cato Guldberg

Earth Sciences
Jakob Bjerknes
Vilhelm Bjerknes
Peter Waage

Physics
0

Math
Niels Abel
Marius Lie
Caspar Wess

Medicine
Johannes Fibiger

Technology
0

Finland -- 1 Significant Figure

Astronomy
0

Biology
0

Chemistry
0

Earth Sciences
Johan Gadolin

Physics
0

Math
0

Medicine
0

Technology
0

Ireland -- 13 Significant Figures 

Astronomy
William Parsons

Biology
John Tyndall

Chemistry
Thomas Andrews
John Bernal
Adair Crawford

Earth Sciences
Francis Beaufort
Edward Sabine

Physics
George Fitzgerald
George Stokes
George Stoney
Ernest Walton

Math
0

Medicine
0  

Technology
Arthur Kennedy
Charles Parsons

 I looked at General Social Survey data to see how much IQ has declined in the US since the early 70s when the GSS was started. I set whites tested in the 70s to a mean of 100, so they are the comparison group. Here's what I found: 

Mean IQ for the 2010s is 99.6, so compared to 1970s whites, the mean has dropped very little. It didn't drop more since we see a Flynn effect among all racial groups. The negative impact occurs because of the tremendous growth of Hispanics who have a 2010s mean IQ of 94 shown below. (All numbers exclude immigrants since they are likely to do poorly on an English-language IQ test). 

Some people argue that mean IQs for whites and blacks differ because blacks tend to come from poorer families. A black kid raised with resources equal to a white kid will have the same IQ. Is this the case? 

Using data from the General Social Survey, I calculated mean IQ for blacks, whites, and others for several ranges of father's socioeconomic index (SES): 1-2 standard deviations (sd) below average, 1 sd below average to average, average to 1 sd above average, 1-2 sds above average, and over 2 sds. The sample size is 12,016 (immigrants were excluded). Here's a graph that summarizes the results: 

Blacks and whites raised at the same SES level do not have the same mean IQs. The higher white average ranges from about 7 points among the poorest group to more than 10 points among the wealthiest group. By the way, other non-whites--mostly Hispanics--are closer to blacks than whites. 

DGo (@Go321) on Twitter wondered which lower IQ groups still manage to be well-behaved as groups. Criminality is a decent measure of behavior, so I looked at General Social Survey data to see which groups with low average IQs also have lower than average arrest rates: 

The percent arrested for the whole country is 12.7%. The groups listed above with an arrest rate lower than that are: Filipinos, West Indians, and Non-Spanish West Indians. And let me add that these three groups have IQ means that are not very low: 96.7, 98.8, and 95.9, respectively. 

Most lower-IQ groups have high arrest rates, as expected.

UPDATE: After checking, I see that Arabs do not have a low mean IQ: it's 102.   

 Someone at Twitter, I forget now, wondered if IQ or one's social class was more important for adult success. Well, the General Social Survey can help with this. I threw in basic demographics as controls. 

Here are OLS results for income:

Looking at the betas, you can see that IQ is more strongly predictive of income than father's socioeconomic status (PASEI). Notice how race is not statistically significant when IQ is included in the model. 

And job prestige? 

IQ is much more predictive of job prestige than father's PASEI. 

The results for education should be even stronger for IQ:

The beta for IQ is much larger than for dad's social class. How far one goes in school depends much more on brains than dad's wallet (or his other influences). 

To answer this question, I calculated mean IQs for all self-described whites by the country they said their ancestors came from. Only people born in the US are included since immigrants are at a disadvantage on a vocabulary test (the measure of IQ used here). Here are the results:

Mean IQ

Africa  93.4
Mexico  90.0
Puerto Rico  93.2
Spain  97.2
American Indian  94.7
India  95.8
Other Spanish  95.9
American only  90.4

It looks like many of these people are racially mixed. They label themselves as white but often have some non-white ancestry. The mixed groups that do not have low mean IQs are self-described whites whose ancestors came from east Asian countries--Japan, China, or the Philippines. 

UPDATE: The mean IQ for self-described whites whose ancestors are from east Asia is 99.8. 

Based on the General Social Survey, if you ask Americans where their families originally came from, they will typically give you an answer. But about 1% of whites and 13% of blacks will tell you they are "American only." 54% of whites who give this answer live in the South, and Americans of Scots-Irish ancestry are known to sometimes give this answer. By contrast, "American only" blacks are concentrated in the mid-Atlantic and East North Central regions. 

And their mean IQs? 

Wow, it's around 90 for whites. That is low. 

I wouldn't generalize these findings to the Scots-Irish. Many of the whites, and perhaps some from other races, who say "American only" are probably from lower IQ families who simply have not kept track of where their people are from. Or lower IQ people might be more likely to prioritize their American identity. 

 In "The Son Also Rises," Gregory Clark presents historical data that suggests that French Americans are an underprivileged minority. They have been underrepresented among doctors and lawyers, for example. 

Do General Social Survey data support this view? 

Here are mean years of schooling for the French versus other white Americans:

No difference in education. Here's median income in 1986 dollars:

A lower median income for Americans of French descent. And mean job prestige:

The French have a slightly higher mean job prestige. And IQ?

Basically the same mean IQ.

Clark predicted to the French would eventually move to average levels. It looks like they've made it.  

Someone claimed on Twitter that the mean IQ of American Jews has been falling due to intermarriage. What do General Social Survey data have to say? Here are mean IQs by decade since the 1970s:

No evidence of a decrease here. 

 Another IQ issue arose on Twitter today: Does IQ explain the disproportionate number of Jews in high positions in the new Biden administration? Or is there some other factor? The General Social Survey can't answer this specific question, but we can look at job prestige in general. The table below shows that at the same IQ level, Jews tend to have noticeably higher average prestige scores than non-Jews. 

So, according to GSS data, Jews tend to have characteristics beyond IQ that boost their job prestige. What would those be? I'd be guessing, but in the case of Biden, it might not be a coincidence that most Jews are Democrats and are a key presence in the Democrat Party. My impression is that Jews are very achievement-oriented and are drawn to centers of power. In addition to that, I suspect that a Jew is also likely to enjoy the benefit of being born into a social network of high-achieving people. Connections matter.  

The question was raised on Twitter the other day about whether more education causes increases in IQ. The General Social Survey can help a little with this. Below we have a chart of the mean years of schooling completed since 1977. The mean starts out at 11.71 and ends in 2018 at 13.89 years of education. Over the period, that is an increase of 19%. 

 According to conventional economic theory, growing up in a large family predicts less income as an adult because parents were unable to invest as much in each child. By contrast, genetic theory would predict that that family size would not matter for how much income you earn as an adult; rather, income would be predicted by one's IQ. Let's test these two competing hypotheses using General Social Survey data. 

Respondents were asked how much income they earned in the past year, and they were also given a ten-word vocabulary quiz, which makes a decent proxy for IQ (N = 19,902).

This table shows the estimates for a regression model that includes personal income in constant dollars as the dependent variable and the number of siblings as the predictor. You can see that each additional sibling results in a predicted reduction in one's income of $1,139.  (I believe these are 1986 dollars.)

Looking at this table above, we can see that IQ is positively related to income, and the beta indicates that the relationship is of considerable magnitude. It is predicted that each additional IQ point will result in an additional $423 in income. 

The unstandardized coefficient for number of siblings has dropped from $1,139 down to only $586. In other words, much of the reason why a large family predicts a smaller income is due to the correlation between having many siblings and having a lower IQ. This finding supports, to some extent, the genetic hypothesis. On the other hand, we see that the sibling coefficient is still statistically significant, so even after controlling the influence of IQ, the number of siblings is still negatively correlated with income. The economic hypothesis appears to have something to it. 

 Using 2018 General Social Survey (GSS) data, I looked at the relationship between confidence in the existence of God and IQ as measured by a vocabulary quiz:

The IQ average for atheists is over 6 points higher than the mean for those who know God exists.  Agnostics, in fact, have the highest average with 103.9. 

Now let's look at fertility by confidence in God for those who are old enough to have completed their family size but are not so old they're really from another generation. Let's choose 45 to 64:

We see that atheists average 1.2 children, while the mean for those who know God exists is 2.1. So believers have families that are 1.8 times bigger than those of atheists.  The believer/agnostic difference is similar.  

We know that general intelligence is highly heritable, so smart people tend to have smart kids. Atheists and agnostics have fewer kids, so, at least under current conditions, skepticism is dysgenic.