IQ Mania (2). Who is the most intelligent person of all time?
Notes on Emil Kirkegaard's list. Part 2
*** Here you can find → Part 1 of this article. ***
As we stressed at the outset, intelligence is not an absolute quantity. IQ can only be interpreted in relation to a specific reference group. As we also pointed out, IQ relates to one’s age cohort because cognitive ability changes across the lifespan. A similar issue arises in Emil Kirkegaard’s survey for a different reason.
The stimulus subjects are, for the most part, contemporary U.S. Americans. For this subgroup, the matter is unproblematic. In addition, however, there are also persons who lived long before our time and in quite different cultures, some more than 2000 years ago. What is the reference group of Socrates, of Thomas Aquinas, of Issac Newton, of Immanuel Kant and the others?
To understand the problem, it is necessary to recall a finding that can justifiably be called one of the most significant discoveries of intelligence research. We are talking, of course, about the Flynn effect.
Flynn Effect
The Flynn effect describes the fact that performance on psychometric intelligence tests improved throughout the 20th century. Since intelligence tests are calibrated to the mean value of 100, increasingly difficult tasks had to be inserted over time.
This phenomenon was already noticed in the first half of the 20th century, but it was only discussed in narrow circles. This changed abruptly when James Flynn published two articles in the influential Psychological Bulletin in 1984 and 1987. In the first article, he showed that the IQ of Whites in the U.S. had increased by about 3 points per decade from 1932 to 1978, while at the same time performance on the SAT college aptitude test, which also measures intelligence, had declined. In the second article, he reported similar growth rates for 14 advanced industrialized countries during periods of varying length between 1932 and 1984.
Suddenly, researchers became aware of the explosive nature of these findings. For centuries in northwestern Europe, the more intelligent classes had more offspring on average than the unintelligent. Among the latter, many were even excluded from reproduction. Thus, a genetic sieving toward higher intelligence occurred over many generations. This trend reversed with the demographic transition that accompanied modernization. Since the 19th century, the less intelligent have had more offspring on average than the intelligent. Therefore, a decrease in the level of intelligence would actually be expected. However, only a very gradual one, since genetic changes occur only very slowly.1 Instead of a minimal decrease, however, a massive increase in IQ was registered.
This apparent paradox triggered a real research boom and the phenomenon got the name Flynn effect, although others had pointed it out before.2 In the meantime hundreds of studies and several meta-analyses are available. The main results can be summarized as follows:
The Flynn effect is not limited to advanced industrialized nations. It is a global phenomenon, albeit at very different starting levels.
In Western industrialized nations, the IQ increase in the 20th century was about 30 IQ points.
In some advanced industrialized nations, there is evidence that the trend has weakened or stalled, or even turned negative.
Figure 1 illustrates the dramatic increase in phenotypic intelligence around the globe.3 It is based on the meta-analysis by Pietschnig and Voracek (2015).
At this point, one could illuminate numerous aspects and get into endless debates. We limit ourselves to a few points that are important for our topic. And for this we come back to Emil Kirkegaard’s list.
Flynn effect and Kirkegaard’s list. From Socrates to Rockefeller.
In Kirkegaard’s survey, the judges were asked to estimate the IQ of 54 people. 45 of them were contemporaries. For these, the Flynn effect plays no role. The other candidates were:
John D. Rockefeller (1839 – 1937)
Friedrich Nietzsche (1844 – 1900)
Immanuel Kant (1724 – 1804)
Isaac Newton (1642 – 1726)
Thomas Aquinas (1255 – 1274)
Diogenes of Sinope (413 BC – 323 BC)
Aristotle (384 BC – 322 BC)
Plato (428/7 BC – 348/7 BC)
Socrates (469 BC – 399 BC)
How should one be able to estimate the IQ of these people?
Some may find the question strange. But it is not. Quite the contrary.
For the sake of simplicity, let’s look at the year 1900. At that time, John D. Rockefeller had long been a multi-billionaire and the richest man in the world; and 1900 is the year of Friedrich Nietzsche’s death. Let’s assume quite arbitrarily that Rockefeller had an IQ of 160 at that time.4 Thus, he would have outperformed 99.997 percent of his age group.
In Part 1, we strongly emphasized that IQ always refers to the age cohort. This raises the question: What was the intelligence level of Rockefeller’s age cohort? And this brings the Flynn effect into play. The literature usually reports an increase of 30 IQ points in the 20th century. If we take that seriously, we would conclude that the average U.S. American of 1900 would score an IQ of 70 at best on today’s intelligence tests. The fictional IQ of 160 would become only an IQ of 130. While our fictional Rockefeller would have outperformed 99.997 percent of his contemporaries, today it would be only 97.2 percent. That would still be superb, but he would have to tremble at the MENSA test.
However, the Flynn effect did not start in 1900 of all years. The increases before that were nowhere near as dramatic as they were in the 20th century, but the further back we wander from Rockefeller to Socrates, the lower the intelligence levels were. If we want to get an idea of the cognitive ability of generations far back in time, we need to look at the Flynn effect in a more nuanced way.
Decomposing the Flynn effect
As early as the seminal 1984 article, Flynn brought into focus the differential growth in psychometric intelligence tests and the SAT study aptitude test, which, after all, also measures intelligence. In 1987, he showed that growth in the nonverbal domain of psychometric tests was nearly twice that in the verbal domain, and this ranking was the same in all 14 countries. This pattern has been confirmed again and again in subsequent studies. This may seem odd at first glance, but it is not. Intelligence is an extraordinarily broad concept that encompasses several facets. The key point is that all these facets correlate positively with each other – people who are good or bad in one area tend to be good or bad in others – so it makes sense to combine the commonality behind the different performances into a global measure of intelligence. Nonetheless, the individual components may evolve independently over time.
In his 2009 book, Flynn outlined the vast differences in the development of various subtests of the Wechsler Intelligence Test for Children WISC.
„Americans gained 24 points on Similarities between 1947 and 2002 (1.6 SDs), 4 points on Vocabulary, and only 2 points on Arithmetic and Information ... The WISC gives not only subtests scores but also a summary judgment on our intelligence called Full Scale IQ. These gains are huge, amounting to about 18 points. The posited gains on Raven’s come to fully 25.7 points“ (Flynn, 2009, p. 9). [Raven’s means Raven’s Progressive Matrices; we will return to this in Part 3. R.H.]
The crucial point can be summarized thus:
Phenotypic intelligence increased massively in the 20th century, but the development was markedly different in different subfields. In some areas, the increase has been staggeringly high; in others, little has changed.
If we want to assess the intelligence of people who lived long before us, we have to take the Flynn effect into account. However, it will not suffice to look at the overall effect; a proper understanding can only be obtained by taking a closer look at the different trends in the individual components.
Before delving into the matter, let’s look back to 1900. Rockefeller’s contemporaries would probably only achieve IQ scores around 70 in today’s intelligence tests. But they were not, of course, on the verge of debility. The same is true of generations back to Socrates and beyond. They were all up to the demands of their time. But in some respects they were hopelessly inferior to us. And because exactly these points were weighted more and more heavily in psychometric intelligence tests, the gap between the (hypothetical) IQ scores became wider and wider.
In Part 3, we will dig even deeper, and in doing so, we will come across some points that hardly any of the participants in Kirkegaard’s survey considered.
Literature
Flynn, J.R. (1984). The mean IQ of Americans: Massive gains 1932 to 1978. Psychological Bulletin, 95, 29-51.
Flynn, J.R. (1987). Massive IQ gains in 14 nations: What IQ tests really measure. Psychological Bulletin, 101, 171-191.
Flynn, J.R. (2009). What is intelligence? Beyond the Flynn Effect. Cambridge: Cambridge University Press.
Lynn, R. (2013). Who discovered the Flynn effect? A review of early studies of the secular increase of intelligence. Intelligence, 41, 765-769.
Pietschnig, J. und Voracek, M. (2015). One century of global IQ gains: A formal meta-analysis of the Flynn Effect (1909–2013). Perspectives on Psychological Science, 10, 282-306. Supplement at https://journals.sagepub.com/doi/suppl/10.1177/1745691615577701
The following remarks will make clear that genetic evolution can explain only a small fraction of the fundamental changes.
For the history of the discovery of the Flynn effect, see Lynn (2013).
Source: Our World In Data, CC BY 3.0 https://creativecommons.org/licenses/by/3.0 ; via Wikimedia Commons https://commons.wikimedia.org/wiki/File:The_Flynn_Effect-_Gains_in_mean_IQ_for_world_regions,_OWID.svg
At that time there were no useful intelligence tests; and as we have seen in Part 1, such a high value cannot be precisely determined empirically at all. But that doesn’t matter for our argument.
I think if you measured past people with present-normed IQ tests, you wouldn't find a nearly-perfect normal distribution. Probably you would find a fat right tail, which weakens the strength of your argument.