Monday, August 6, 2018

Why is IQ declining in the Arab world?

African migrants at the Egyptian-Israeli border (Wikicommons)

During most of the twentieth century people did better and better on IQ tests. This increase, dubbed the Flynn effect, is now plateauing in the Western world. It is even reversing in Scandinavia and France (Bratsberg and Rogeberg 2018; Dutton and Lynn 2015; Flynn 2007, p. 143; Teasdale and Own 2005).

A similar plateauing and even reversal has begun in the Arab world. In Kuwait, mean IQ fell an average of 6.2 points between 2006 and 2015 (Dutton et al. 2017a). In Damascus, it remained unchanged between 2004 and 2013/14 (Dutton et al. 2018a). In Khartoum, it fell an average of 2.13 points between 1999 and 2010 (Dutton et al. 2017b).

Khartoum: is the Flynn effect continuing?

The authors of the Khartoum study later retracted their finding, however. Because the earliest data had been collected just before the introduction of compulsory schooling in 1999, the IQ decline could simply reflect a change in sampling: from middle-class children to children in general. There were also strange age differences: IQ scores declined in some age groups but not in others. So the authors conducted a second study, examining only data from students with a compulsory schooling background. They now found an increase in mean IQ from 2004 to 2016, i.e., a positive Flynn effect (Dutton et al. 2018b).

On the other hand, “compulsory schooling background" may also mean a different ethnic background. When I enquired about this point, Dr. Bakhiet replied that the study was done in residential areas of Khartoum where there were no refugees or immigrants. The participants thus “represent the people of northern Sudan” and were not recruited from among the millions of migrants who live on the city’s outskirts.

As for the first Khartoum study, we know little about the ethnic background of the participants. Some of them seem to have had migrant backgrounds. We should keep in mind that many refugees were initially housed within the city limits and that not all migrants ended up in refugee facilities. Unfortunately, it would be difficult to find out more because the lead researcher, Dr. Omar Khaleefa, was abducted and apparently murdered in 2012. I suspect that this kind of information was not recorded at the time, given the delicate nature of ethnic identity in Sudan.

In sum, the second Khartoum study largely excludes the city’s immigrant population, and it is this study that provides a reassuring picture of rising IQ. As for the first Khartoum study, we know less about the ethnic makeup of its participants, particularly whether their ethnic makeup changed over time. This is an important factor to consider. Khartoum is now overwhelmingly a city of migrants from the south, and it is unlikely that many will ever return home.

Possible causes 

Why this apparent plateauing or reversal in places as different as Khartoum, Kuwait, and Damascus? The authors cite several possible causes:

Emigration, i.e., 'brain drain'

Damascus has lost many educated people because of the civil war. There has been much less of a brain drain in Khartoum and probably none at all in Kuwait.

Muslim curriculum

Both Sudan and Kuwait have introduced a "Muslim curriculum" that focuses on teaching Islam to the relative exclusion of scientific subjects. Damascus students get only two hours of religious education per week.

Differential fertility

This factor has been studied in three Arab countries: Kuwait, Libya, and Sudan. When IQ is compared with number of siblings, there is hardly any correlation in Kuwaitis but a significant negative correlation in Libyans and Sudanese (Abdel-Khalek and Lynn 2008; Al-Shahomee et al. 2013; Khaleefa 2010). Khaleefa (2010) calculated that Sudanese IQ is declining at a rate of 0.8 points per generation because higher IQ individuals have smaller families. This factor may be stronger in Turkey, Lebanon, and Egypt, which are more Westernized.


The Khartoum Metropolitan Area grew from 2.9 million in 1993 to 5.3 million in 2008. This growth was driven overwhelmingly by migration from South Sudan and Darfur, largely as a result of the Second Sudanese Civil War (1983-2005). As a result, “southern” migrants now make up a majority of the population:

This war led to an influx of displaced persons coming into Khartoum from the provinces and from South Sudan, now a separate state. The average IQ of Arab Sudanese with no refugee background around Khartoum has been found to be 77.4, based on UK norms. However, the average IQ of people from the war-torn region of Darfur, which is still within the current Sudanese state, is roughly 64 (Bakhiet & Lynn, 2015). This is similar to IQ estimates for the Southern Sudanese (e.g. Fahmy, 1964, cited in Lynn, 2006), many of whom also fled to Khartoum during the war (Bassil, 2013). Indeed, the genetics of the northern Sudanese is very close to that of Egypt and other North African countries. By contrast the West and south of the country are genetically closer to the Sub-Saharan Africans of South Sudan. (Dutton et al. 2017b)

Meanwhile, Kuwait became more South Asian during this same period. The IQ surveys in 2006 and 2015 thus sampled two significantly different populations:

In 1975, Jordanians and Palestinians were the predominant category comprising about 40 % of the total non-Kuwaiti population, followed by about 12 % Egyptians and 9 % Iraqis. Asians from Iran, India and Pakistan constituted only about 18 % of the non-Kuwaiti population. The Asian presence in Kuwait increased significantly during the late 1970s and early 1980s, resulting in 35 % of the non-Kuwaitis being Asian. After liberation of Kuwait, the percentage of Asians increased further and in 1995, Arabs and Asians each constituted about half of the total non-Kuwaiti population. During the decade of 1995-2005, Arabs lost ground to Asians with the latter comprising almost 59 % of the non-Kuwaiti population in 2007. (Shah 2007)

The Simber Effect

The above studies also show that IQ begins to decline during adolescence in these countries. In people of European origin the decline normally happens later in life:

The second point of interest is that in both samples the SPM score is statistically significantly lower among 18 year olds than it is among 17 year olds. In general, overall performance on IQ tests tends to increase into adulthood, meaning that we would expect 18 year olds to score higher than17 year olds. In this regard, Bakhiet et al. (2018) have identified what they have called the Simber Effect in a meta-analysis of progressive matrices administrations in 12 Arab countries. They found that IQ in Arab countries, relative to European norms, falls between the ages of 7 and 18, when looking within single cohorts. At age 7 it is the same or slightly below European norms but it eventually falls to around a standard deviation below European norms. They have shown this by comparing different cohorts divided up age, not via a longitudinal analysis of one cohort. The raw score declines at this very specific age that we have observed here would be potentially consistent with this gradual fall and they are not unique to Syria. Xhosa SPM score declines between 15 and 16 (Bakhiet & Lynn, 2015). Jordanian Advanced Progressive Matrices score peaks at 18 to 20 and then slowly declines (Lynn & Abdel-Khalek, 2009). In Sudan, SPM score peaks at 17 and then falls (Khaleefa, Lynn, Abulgasim, Dossa, & Abdulraddi, 2010) while in Somalia it also declines after the age of 17 (Bakhiet et al., In press). (Dutton et al. 2018a).

The ability to learn may have originally been a juvenile trait in our species. Childhood was a time when early humans had to learn what to do and what not to do. After puberty, they literally became set in their ways. As societies became more complex, adults had to retain this ability, in the same way they have retained the ability to digest milk sugar wherever dairy farming is practiced.


IQ has recently declined in parts of the Arab world, and several possible causes have been put forward. More research is needed but the following conclusions seem justified:

- Ethnic change is a major cause, if not the leading one. Although we speak of the 'migrant crisis' as a European problem, it is actually part of a larger demographic overflow from sub-Saharan Africa and South Asia, and this overflow is primarily spilling into North Africa and the Middle East. 

- Differential fertility, commonly called dysgenics, is becoming important, at least in some Arab countries. This may be due to Westernization. The upper and middle classes are more likely to follow Western models of behavior, including smaller family size. This is at most a secondary cause of declining IQ in the Arab world.

- The introduction of a 'Muslim curriculum' may or may not be a factor. Its effects on IQ should be studied in a stable Arab population that is not changing through immigration or emigration.

- The Flynn effect may be running out of steam in the Arab world, as it has in the Western world. Other trends are thus becoming visible, and those trends are largely negative. 

In itself, the end of the Flynn effect is no cause for worry. It probably does not correspond to a real increase in cognitive ability. People have simply become more adept at taking tests, including IQ tests.

Just think. Beginning at least in the 1930s the Flynn effect added around 3 points each decade to average IQ until the 1990s. Such a huge gain—18 points—should be visible in the evolution of popular culture. Yet popular culture didn't become higher-brow during that period. In fact, from the 1970s onward it became lower-brow. In magazines, fonts became bigger and sentences simpler and shorter. In movies and sitcoms, plots became less complex, and characters shallower. You could counter-argue that popular culture was now embracing the interests of ordinary people, after long being elitist, but that isn't my impression. In the 1970s I often met ordinary adults with intellectual hobbies of one sort or another, like stamp collecting, ham radio, science fiction, field naturalism, astronomy, and so on. My father had a working-class background, yet he had all the works of Ray Bradbury, plus earlier works by H.G. Wells and Jules Verne. Ordinary people like that are now hard to find, even though IQ scores have risen considerably between then and now.

This is another reason why, in the nature versus nurture debate, twin studies overestimate the latter's importance. "Nurture" is simply the residue of everything that's not nature: not only your learning environment but also your familiarity with test-taking, as well as errors in calculating test scores or differences in scores due to the way the tests are administered.  

On a final note, we need more research on IQ in the Arab world. Unfortunately, there, as here, such research is not without risk. Omar Khaleefa, at the University of Khartoum, did many pioneering studies on this subject in Sudan, including his calculation that Sudanese IQ is declining at a rate of 0.8 points per generation. He disappeared six years ago. His body was never found, and no demands for money were ever made, as is usually the case with abductions. His family holds the government responsible:

Professor Omar Haroon Al Khaleefa left his home in an upscale neighborhood of Khartoum North and was never seen again. His family holds the Sudanese authorities responsible for his disappearance, saying they have failed to investigate new information that has come to light. (Abdin 2014)

Please note:

I may or may not be posting over the next three months. This is a temporary situation, and I will resume regular posting in November.


Abdel-Khalek, A.M., and R. Lynn. (2008). Intelligence, family size and birth order: Some data from Kuwait. Personality and Individual Differences 44: 1032-1038.

Abdin, T. (2014).  Sudan: The Case of the Missing Professor. AllAfrica, May 22

Al-Shahomee, A.A., R. Lynn, and S.E. Abdalla. (2013). Dysgenic fertility, intelligence and family size in Libya. Intelligence 41(1): 67-69. 

Bratsberg, B., and O. Rogeberg. (2018). Flynn effect and its reversal are both environmentally caused. Proceedings of the National Academy of Sciences Jun 2018, DOI: 10.1073/pnas.1718793115 

Dutton, E., and R. Lynn. (2015). A negative Flynn Effect in France, 1999-2008-9. Intelligence 51: 67 -70. 

Dutton, E., S. Bakhiet, Y. Essa, T. Blahmar, and S. Hakami. (2017a). A negative Flynn effect in Kuwait: The same effect as Europe but with seemingly different causes. Personality and Individual Differences 114: 69 -72.

Dutton, E., S. Bakhiet, K. Ziada, Y. Essa, and T. Blahmar. (2017b). A negative Flynn Effect in Khartoum, the Sudanese capital. Intelligence 63: 51 -55.

Dutton, E., Y.A.S. Essab, S.F. Bakhietb, H.A.A. Alib, S.M. Alqafarib, A.S.H. Alfalehb, and D. Becker. (2018a). Brain drain in Syria's ancient capital: No Flynn Effect in Damascus, 2004-2013/14. Personality and Individual Differences 125: 10-13

Dutton, E., S.F.A. Bakhiet, H.A. Osman, D. Becker, Y.A.S. Essa, T.A.M. Blahmar, R. Lynn, and S.M. Hakami (2018b). A Flynn Effect in Khartoum, the Sudanese capital, 2004-2016. Intelligence 68: 82-86.

Flynn, J.R. (2009). Requiem for nutrition as the cause of IQ gains: Raven's gains in Britain 1938-2008. Economics & Human Biology 7(1): 18-27.

Flynn, J.R. (2007). What is Intelligence? Beyond the Flynn Effect. Cambridge University Press.

Khaleefa, O. (2010). Intelligence in Sudan and IQ gain between 1964 and 2008. ArabPsyNet E-Journal 25-26: 157-167.

Shah, N.M. (2007). Migration to Kuwait:  Trends, Patterns and Policies. Paper Prepared for the Migration and Refugee Movements in the Middle East and North Africa. The Forced Migration & Refugee Studies Program. The American University in Cairo, Egypt. October 23-25, 200

Teasdale, T.W., and D.R. Owen. (2005). A long-term rise and recent decline in intelligence test performance: The Flynn Effect in reverse. Personality and Individual Differences 39(4): 837-843.


Sean said...

Re Mr Khaleefa, intelligent people will tend to leave such countries, and according to Paul Collier emigration of the most intelligent starts a vicious circle.

Anonymous said...

The civic nationalists & Western advocates won't like the implications of this: it is non-Europoid (black) immigrants who have decreased the IQ of Europoid (white) Moslem countries, and Western values actually weaken their elites?

Anonymous said...

Those are some very interesting facts. I wish these in- and decreases by age and the std dev of different populations were centrally collected like the mean IQ scores.

About the Flynn effect: Roughly, our brain does three things: Bottom up (spatial) pattern recognition, lateral sequence handling, and top down framing aka understanding. Pattern recognition ability is amenable to just having more pattern recognisers i.e. a larger brain. The other two abilities are much more restrained by the ability to quickly create synapses etc. Average brain size has increased by more than a standard deviation in the last century or so. The Flynn effect has operated on tests of pattern recognition and hasn't really touched sequence handling test, like verbal ability or digit span. That's why I'm pretty sure that the Flynn effect is a direct effect of brain size increases. If better test taking ability were the main cause, it should be possible to emulate the Flynn effect in intervention studies. But that doesn't seem to be possible. I don't think the Flynn effect is hollow, but spatial pattern recognition doesn't seem to be very important in most aspects of life.

Anonymous said...

Why is Iran considered an Asian country and Iraq, Jordan and Palestine aren't? Makes no sense.

Anonymous said...

Anon, the Russians usually consider Iran to be in Central Asia, not the Middle East/Levant. Probably this has to do with the nation's position on the Silk Road and the past extent of Iranian languages around that region.

Anonymous said...

About the Simber effect: If that is correct it would make inbreeding depression an unlikely cause of the low Arab IQs. Same with sub-saharan admixture. One would have to bet that it is mostly due to different selection pressures. Also, it would be very interesting to look for a Simber effect in other muslim populations. I don't think the Turks show something like that.

J said...

You are right, the current wave of outmigration of Africa is a general trend and it is hitting harder Arab countries with terrestrial borders. In all places, Africans just walk in and stay. On the other hand, they may reduce the average IQ and per capita GNP, but they improve the life of the established elite.