Sunday 27 March 2016

What intelligence researchers think about heritability


I discussed this survey of intelligence researchers in December 2013

Asked: Is there sufficient evidence to arrive at a reasonable estimate of the
heritability of intelligence in populations of developed countries?” 73% said Yes.

Asked: What are the sources of U.S. black-white differences in IQ?

0% of differences due to genes: (17% of our experts)
0-40% of differences due to genes: 42% of our experts
50% of differences due to genes: 18% of our experts
60-100% of differences due to genes: 39% of our experts
100% of differences due to genes: (5% of our experts)
M=47% of differences due to genes (SD=31%)

Now we have the first publication on this survey:

Survey of Expert Opinion on Intelligence: Causes of International Differences in Cognitive Ability Tests Heiner Rindermann David Becker and Thomas R. Coyle

Intelligence March 2016 | Volume 7 | Article 39

Following Snyderman and Rothman(1987,1988), we surveyed expert opinions on the current state of intelligence research. This report examines expert opinions on causes of international differences in student assessment and psychometric IQ test results. Experts were surveyed about the importance of culture, genes, education(quantity and quality), wealth, health, geography, climate, politics, modernization, sampling error, test knowledge, discrimination, test bias, and migration.The importance of these factors was evaluated for diverse countries, regions, and groups including Finland, East Asia, sub-Saharan Africa, Southern Europe, the Arabian-Muslim world, Latin America, Israel, Jews in the West, Roma (gypsies), and Muslim immigrants. Education was rated by N=71 experts as the most important cause of international ability differences. Genes were rated as the second most relevant factor but also had the highest variability in ratings. Culture, health, wealth, modernization, and politics were the next most important factors, whereas other factors such as geography, climate, test bias, and sampling error were less important. The paper concludes with a discussion of limitations of the survey (e.g.,response rates and validity of expert opinions).

Differences between countries with the lowest and highest ability levels are large. For example, in TIMSS 2011, 4th grade Yemeni pupils achieved 209 student assessment study (SAS) points, whereas South Korean pupils achieved 587 SAS points. If SAS points are converted to IQ points, the Yemeni would have an IQ of 56 and the Koreans would have an IQ of 113, a difference of 11 years of schooling. Psychometric IQ studies show similar results. For example, Malawi has an estimated IQ of 60, whereas Singapore and Hong Kong have estimated IQs around 108, a difference that translates into SAS≈233 and 555 or 16 years of schooling.

When authors give ability differences as “years of schooling” this always provokes the response that countries with lower levels of ability need more schooling. It really means “despite schooling, as if they permanently required 16 more years of schooling”. The main reason that intelligence is not a popular subject is that it has been shown not to be very malleable. At a rough estimate, anyone of IQ 93 and below finds it difficult to earn good wages.

The authors explain that: the conversion transforms the SAS-scale (M = 500, SD = 100) in developed countries to an IQ scale (M = 100, SD = 15). We assumed an increase of 35 SAS points, or 3 IQ points per year of schooling (Winship and Korenman, 1997; Rindermann, 2011).

In the current study, data collection procedures were designed to ensure anonymity. The anonymity was implemented to reduce pressure for socially desirable responses, and to increase the likelihood of obtaining honest opinions. Opinions made in anonymity (without fear of retribution) may differ from public appraisals such as those reported in Gottfredson’s (1994) “Mainstream Science on Intelligence,” which was signed by more than 50 researchers.



Notice of the study was emailed to experts who published articles on or after 2010 in journals on intelligence, cognitive abilities, and student achievement. The journals included Intelligence, Cognitive Psychology, Contemporary Educational Psychology, New Ideas in Psychology, and Learning and Individual Differences. Notice of the study was also emailed to members of the International Society for Intelligence Research (ISIR), and posted to the web site for the International Society for the Study of Individual Differences (ISSID). ISIR and ISSID support intelligence research and host professional conferences with intelligence researchers. Finally, the study was announced at the 2013 ISIR conference in Melbourne, Australia. A total of 1345 people received an email invitation. An expert was defined as a person who had published on cognitive ability or who had attended intelligence conferences and presented research. Compared to Snyderman and Rothman (1988, pp. 46–49), our selection criteria were based more on publications in specific scientific journals and less on membership in scientific organizations. In addition, we used email and a web based survey rather than traditional mail and paper-pencil surveys.

The low response rates may be attributed to the length of the survey (which took about 40–90 min to complete), self-censorship, or fear of addressing a controversial subject (despite assurances of anonymity). The low response rates may also reflect a paucity of experts on intelligence and international differences in cognitive ability. There may be 20–50 scientists who study international differences in intelligence. Based on this estimate, the number of respondents (71 people) may exceed the number of scientists who study the topic!

Speaking personally, I found the survey too long, and too interested in subtle points of distinction between various ways of describing intelligence. However, I am easily bored.

Around 90% of experts believed that genes had at least some influence on cross-national differences in cognitive ability.

National IQ causes

As you can see, experts back genes, education quality and quantity, culture and health, plus a scattering of other causes as being the reasons for national differences in ability.

Assuming that the survey is representative of expert opinions, genetic factors should receive more attention in future research and public debates. To fairly consider different hypotheses, future research should incorporate procedures (e.g., rules for methods of argumentation) that reduce zeitgeist or political pressures that may bias responses on controversial issues (e.g., Segerstråle, 2000; Jussim et al., 2015).

Education was measured with two items, environmental factors with 11 items, and genetics with one item. To better estimate the importance of nature and nurture, a single binary question could be added to future surveys (e.g., “Which is more influential, genetic or environmental factors?”).

A single empirical study can contradict expert opinion, and the results of the current survey must be validated in future empirical research.

This last observation is crucial. Expert opinion is no more than an indication of the current state of the argument among informed persons. A new discovery can change the argument. More genetic research, particularly on racial differences on intelligence (which as far as I know has never been funded) would be very likely to strengthen the genetic interpretation, but a negative result would be very interesting. Solid proof of environmental manipulations and educational techniques to overcome national and racial differences in intelligence would swing the argument in favour of environmental explanations.

Perhaps we should predict what such a survey will find by 31 December 2020. I assume there will be no funding for such research, and that results will have to be obtained by making assumptions about censored data. I am not a super-forecaster, but I think that genetic explanations for national and racial differences in intelligence, as shown in Table 1, will rise from 20% to 30% but the standard deviation will remain just as large.  

What are your precise predictions?


  1. I try to follow this topic closely on the web and I can't think of the last study that was touted as supporting the culture only theory.

  2. My precise prediction is that such research will be funded in China and will produce the result that (almost) everyone knows to be true but many dread to admit.

    That will be followed by a wonderful display of anti-racists saying you can't believe any result published by Chinamen.

  3. elijahlarmstrong27 March 2016 at 19:23

    Pedantic note: Ranking factors such as education, genetics, etc. by percentages is problematic, since the true factors may be nonadditive and impossible to cleanly separate. Also, "genes" explain much more of the results if you include G-E correlation (e.g., a nation with more low-IQ alleles ––> is poorer ––> has an even lower IQ) than if you just include "direct" genetic effects.

  4. Neither pedantic nor NIT-picking. The authors confess as much: Finally, the expert survey did not address the interdependence of factors. Factors related to cognitive ability may influence each other in complex ways. For example, culture may influence education, genes, health, and cognitive ability, which in turn may influence wealth and economic development (e.g., Rindermann et al., 2013, 2015). These interdependencies could be examined using path models and longitudinal datasets.

    1. elijahlarmstrong27 March 2016 at 20:32

      Ah, my mistake.

    2. It seems from Prof Greg Hsu's research that the interdependence of genes is questionable. The graphic results appear to represent thousands of independent switches that are either on or off. Culture, however, could drastically affect the value of intelligence, leading to negative feedback in some cases.

  5. 2020? An increase by 20-30%? No way. Way too soon. That would require ~25% physical change in the population of the said researchers - clearly unrealistic number for [mostly] tenured folks.

    1. I was assuming that some people would change their mind, if only on anonymous surveys.

    2. If they already haven't, the chances of that happening on account of more studies coming out are pretty slim. It's not like scientific position is primarily based on facts :-) Self-deceit is a powerful force.

  6. Cultures that emphasize hard working may perhaps have an increase in average intelligence (cognition) because people have to micro-adjust while cultures which have different life styles may have another effect. Speculation of course. This effect can be critical depending on the subgroup of psychological and cognitive combinations.

    Personality influences cognition (measured by cognitive tests).

    It is analogous to the anxious people who can not make the cognitive tests for optimum results or in the case of people with bipolar disorder, which they present different scores depending on the mood.

    In the most, it is the usual, intelligence is not just the job potential and is what the IQ tests measure. IQ tests measure potential and directed to work. But intelligence should never be summarized the efficiency at work or even to your '' potential '', if we can set this way.

    We are accustomed to the subjective and peaceful world in which we are born and being destroyed. The reality is now. Who can not recognize strengths and weaknesses, recognize the weaknesses and strenghts of others, know how interact and the reality or dynamic in which he lives, will be taken by lucky breaks + super-structure that catapult the most efficient workers for socio-economic security positions but will not come with based on own talent for survival.

    That's why emotional intelligence is more correlative with individual success than IQ, if we are social species, it will be expected that the more emotionally intelligent are better to accumulate advantages in social environment.

    Perhaps it makes sense to think reflectively, for you guys of course, about the '' theory '' of the multiple intelligences or cognitive specificities to look for associations between genes and intelligence (s).

    1. ''We are accustomed to the subjective and peaceful world in which we are born and being destroyed''

      Wesstern of course, ;)


      Multiple and emotional intelligence add about 1% to the accuracy of job selection processes

    3. why you took my comment ***

    4. I'm expecting a HONEST answer, please.

      Scientists dislike real imagination.

  7. The 17% of experts that think genes account for 0% of IQ differences can be pretty noisy. Personally I don't call them experts but "guardians of the faith".

  8. This comment has been removed by the author.

  9. IF the question were: "how much of the B-W difference in crime, academic and job performance is due to environmental effects on Blacks that could be changed to reduce the gap?" then the answer might well be a negative number, as we're already doing as much as possible and well past the point of net benefit to society, and without those environmental supports, Blacks would be performing worse, approaching African levels of worse.

  10. My guess is that within a few years, the answer will either be 80% or it will be 0% if you can even get experts to fill out the survey.

  11. Come, now. All progressive thought, authority and thought authority now agree that the concept of race is as culture-bound as geography, and intelligence is as relative to differing norms as altitude. Indeed, such regressive notions as geography and altitude are often associated with hateful reactionaries who maintain that there are geographical and even altitudinarian absolutes. "Assistant Village Idiot" and "reiner Tor" at West Hunter handled these pernicious misconceptions admirably back in 2013:

    Assistant Village Idiot: Altitude is a notoriously difficult concept to define. It is highly culture-bound. Do you mean altitude above the base of the mountain, as in Mauna Loa, the height above sea level, the distance from the center of the earth, the height above the nearest inhabited area, or some other definition of altitude? Modern thinkers prefer to speak in terms of “multiple altitudes.” A person born at a lower elevation may have had to climb a greater distance to get to 10,000 ft or 15,000ft. (Reported altitudes higher than that should be regarded with suspicion.) And are we sure it is the alleles, after all? People born at certain privileged altitudes might be merely defining their own mountains as “highest.” Additionally, their children might only seem to be better adapted to altitude because of better nutrition, plumbing, and access to medical care. Bringing pre-K children up mountains under government sponsorship might be more effective than looking for some purported genetic connection.

    reiner Tor: Also, when talking about “altitude of geographical regions”, you need to ask: what is a geographical region? Is it even relevant to “altitude”?

    The famous scientist Lewontin has shown that distances within a certain geographical region can be much higher than between two regions. Take for example Sichuan and Tibet. The distance between Chengdu (the capital of Sichuan) and Lhasa (the capital of Tibet) is 2079 kilometers. However, the distance between Ngari and Qamdo (two Tibetan cities) is 2142 kilometers. (And Tibet is even larger than that!) Moreover, if you are on the border between Sichuan and Tibet, than the distance between the two provinces falls to zero! Any part of Tibet or Sichuan will be more distant from the border than the border itself. Amazing, isn’t it? And that’s not everything.

    As we now know, people have called an ever changing area “Tibet” or “Sichuan”. Some Tibetans still think that the Garze Tibetan Autonomous Prefecture to be part of Tibet. Historically, the border between the two has never been stable. So basically both historical regions are mere social constructs.

    It is also well-known that however you measure it, the altitudes within a given geographical region can widely differ, according to where you measure it. How can you say that Tibet is higher than Sichuan, when Sichuan’s highest peak is already above 7,500 m, whereas there are points in Tibet below even 3,000 m?

    In other words, just as altitude doesn’t even exist, neither does geographical region, and the “altitude of a geographical region” is a totally meaningless concept. Those who say that “Tibet is higher than Sichuan” are not even wrong.

    What is sure is that the geographical region covered with snow (the white region) is the cancer of the Earth. Regions of color have unfortunately been always oppressed by the white region, so it needs more diversity: the snow needs to be molten so that it gets more brown.