People who live in countries where disease is rife may have lower IQs because they have to divert energy away from brain development to fight infections, scientists in the US claim.
The controversial idea might help explain why national IQ scores differ around the world, and are lower in some warmer countries where debilitating parasites such as malaria are widespread, they say.
Researchers behind the theory claim the impact of disease on IQ scores has been under-appreciated, and believe it ranks alongside education and wealth as a major factor that influences cognitive ability.
Attempts to measure intelligence around the world are fraught with difficulty and many researchers doubt that IQ tests are a suitable tool for the job. The average intelligence of a nation is likely to be governed by a complex web of interwoven factors.
The latest theory, put forward by Randy Thornhill and others at the University of New Mexico, adds disease to a long list of environmental and other issues that may all play a role in determining intelligence. Thornhill made the news in 2000, when he coauthored a provocative book called A Natural History of Rape in which he argues that sexual coercion emerged as an evolutionary adaptation.
Writing in the journal, Proceedings of the Royal Society, Thornhill and his colleagues explain that children under five devote much of their energy to brain development. When the body has to fight infections, it may have to sacrifice brain development, they say.
To test the idea, Thornhill’s group used three published surveys of global IQ scores and compared them with data from the World Health Organisation (WHO) on how badly infectious diseases affect different countries. The list included common infections, such as malaria, tetanus and tuberculosis.
The scientists found that the level of infectious disease in a country was closely linked to the average national IQ. The heavier the burden of disease, the lower the nation’s IQ scores. Thornhill believes that nations who have lived with diseases for long periods may have adapted, by developing better immune systems at the expense of brain function.
“The effect of infectious disease on IQ is bigger than any other single factor we looked at,” said Chris Eppig, lead author on the paper. “Disease is a major sap on the body’s energy, and the brain takes a lot of energy to build. If you don’t have enough, you can’t do it properly.”
“The consequence of this, if we’re right, is that the IQ of a nation will be largely unaffected until you can lift the burden of disease,” Eppig added.
“It’s an interesting and provocative finding,” said Geraint Rees, director of the UCL Institute of Cognitive Neuroscience. “It explains about 50 to 60% of the variability in IQ scores and appears to be independent of some other factors such as overall GDP.”
“The authors suggest that more infectious disease could lead to lower IQ scores through an impact on brain development. This is an interesting speculation, but the data don’t prove it one way or the other,” he said. “A bigger problem is that it might be driven by a third factor, that affects both infectious disease prevalence and IQ test scores.”
For reasons that are unclear, IQ scores are generally rising around the world. Thornhill suggests monitoring rates of infectious diseases in nations as they develop, to see if they decline and IQ tests scores rise.
Richard Lynn, professor of psychology at Ulster University, and author of the 2002 book, IQ and the Wealth of Nations, said disease and IQ is a two-way relationship, with low national IQs being partly responsible for widespread infectious diseases.
“In recent decades, HIV has been a serious infectious disease, and it has a high infection rate in low IQ countries, especially in southern Africa, where it is present in around 30% of the population … This is attributable to the low IQ of the population who do not understand the way the infection is contracted, and have erroneous beliefs about how to prevent infection.”
Source: www (dot) guardian (dot) co (dot) uk
Also, a friend of mine suggested to check out the following talk by Esther Duflo:
Don’t you think the so-called scientists are being too deterministic?
Read the biased article, no direct correlation between the variables the author mentioned…besides IQ tests are too narrow as they solely focus on the values of Western civilization but overlook achievements of the rest of the world…yes we know that to survive in NYC u gotta hustle so what do you survive in the Kalahari desert … See morelike the San people? What does he say of the Maasai of Ngorongoro Crater living with lions? Isn’t that high IQ based on understanding then conquering their environment?…Man, I really despise generalization science…Anyway, it’s just a theory and we shouldn’t take it too seriously.
Let me start by saying that it is very hard for Social Scientists to impress “real” scientists such as yourself [blogger].
Now, the authors of the paper (which I took the time reading the abstract) are not unconventional in their thinking. The major issues raised in the criticism of the research include whether IQ measures objective intelligence… See more and whether diseases affect brain development they way they see it does. Now I know nothing of neuroscience, however, from a layman’s point of view, the idea seems very logical.
But regarding the IQ issue, what we would like to do is isolate environmental factors that affect intelligence, such as education, type of parents (i.e. by their level of education and so on), health, income of the household and so on.
What social scientists would like to do is run experiments like the “real” scientists do. Have control and comparison group. Randomly select subjects into either group. Vary the variable of interest, in this case, education, or parents, income and so on, and observe changes in intelligence. Now, most of us can agree that IQ is not the best proxy for intelligence, but even other objective tests of cognitive and non-cognitive abilities that are independent of culture, language and so on, show that IQ is a good predictor of intelligence. In other words, IQ is highly correlated with these other tests of intelligence, which is a plus for using IQ.
Now, of course, we are not God, and we cannot randomly select children into what parents they get born into, or randomly assign income among a population, however, some of these things we can randomize, withing bounds of reason and ethics. And people have started to do this in Economic Development.
Now, if we can imagine that education systems really do not vary much across the world, i.e., Algebra is still algebra in Munich as it is in Nzega, then the research results are interesting and should be examined more deeply.
The authors are not claiming that you, having experienced the diseases you have told us you experienced, will be dumber but that on AVERAGE people who experience considerable illness in their first formative years of life will tend to be less able to do Math, or understand the intricacies of language.
I, too, Sir had most of these maladies you had (excluding degedege, however, I had something much worse and never truly diagnosed), and I do not enjoy Math or Physics. I am not very particularly good at either. I cannot write good prose or poetry. Hence, in Tanzania, a place commensurate with the authors’ hypothesis, you are above the average (bringing the average up), I on the other hand am below the average, bringing it down.
These authors are not claiming any racial ranking, but rather argue the contrary: That these same kids if they had been randomly selected to be born in the other parts of the world where disease is not rampant, would have done better. That is an argument against racism as any you will find.
Please be more forgiving of social science, as it is incredibly hard to find causal relationships in the absence of randomized experiments, as we know, human behavior is confounded by many complex issues.
And @ Vin, generalized science is truly the best way to argue systemic relationships that help us understand the world. The randomized trials that Duflo and her colleagues at MIT have pioneered are very specific to the locations they do them in, and even some of their studies have admitted that replicating some of these studies elsewhere yields different results, i.e., introducing textbooks in rural Kenya is not as effective as doing it in rural West Bengal, India and so on.
That’s someone who knows how to debate. While I am digesting your views, I think it would be a nice idea (for the debaters) to read the comments of “Liam23”.. for the (good) sake of having a fairly balanced debate; and hopefully learn a few things from the article:
http://www.guardian.co.uk/science/2010/jun/30/disease-rife-countries-low-iqs
Imagine, after a couple of decades our kids will have to indicate the number of times they have had malaria when applying for universities abroad.
Carlos said; I think that an important point is being missed, if there were no races and someone made the assertion: “people living in tropical climates are more susceptible to disease at a younger age in a period of critical development of the brain” I’m sure the theory would be easier to accept. from a scientific standpoint I believe that the theory makes enough sense for experiments to be taken out. obviously there are more places along the tropical equator then just Africa, there are many places in Latin american and Asia as well that would fall into the study.
@Carlos, you make a good point, probably the issue of race that he kinda of thrown in, gives the picture a whole different look. I have problem with him on the issue of Hiv/ Aids. It seems that he has done little research, on why people “do not understand the way the infection is contracted, and have erroneous beliefs about how to prevent infection.” He didn’t look at other factors, which could be, lack of education, poeple’s cultures, etc etc. I dont think it has anything to do with IQ. That argument is racist, simply because other races other than white have always been looked at as being inferior and people have done everything to justify their claims.
I would like for him to talk about the US, for example, does heis research show the African American & Gays to have low IQ? These two groups are the most affected groups by this disease right. This is when I agree with Charles that, ” this is a direct result of research and theories being formulated by some people abt other people (not themselves). A good example is the theory that stood for a centuries that Jewish slaves built the Giza Pyramids, only for an Egyptian scientist to debunk it“.
He needs to broaden his research, and not pick & choose. For example, the Japanese people seem to be very smart, since they have advanced technologically more than Americans. However, most of its population still have health problems because of the atomic bombs that bombed two of their cities. I want him to talk about the developed world as well, than trying hard to paint other people (third world specifically) as bunch of savages.
I am not quite sure why I don’t agree with the article. But I do believe if the article was written in a certain proper way, I honestly don’t think it would be an issue as far as I am concerned… I would have preferred to read and understand the methodology used (its strengths and weaknesses etc.); and the fact that they only SPECULATE after observing a CORRELATION between two or three data sets they ‘chose’ to take into account should have been mentioned and emphasized. We all know that not everyone out there can think for him/herself. And most importantly, not everyone really understands statistics methodologies.
“Please be more forgiving of social science, as it is incredibly hard to find causal relationships in the absence of randomized experiments, as we know, human behavior is confounded by many complex issues.”
Yea, I understand that and that might be the main problem — trying to understand everything without having any tangible proofs.
I dont think most people would be attacking the article if it were along the following lines..
‘People who have had a certain tropical disease [let’s say between the age of 1 and 7] are likely to have impaired cognitive development. This is SUPPORTED by the study which shows a significant decrease of neuron cell connections… It is clearly evident that neuron cell connections or networking affect cognitive processes etc etc.’
So, why only throw in IQ tests in there? Is it the right method to judge intelligence (while we don’t even have a proper definition of it…)? I can recall one qn in sample IQ tests I saw while I was in high school (O-level): “How many states are there in the US?”. The same goes for other standardized tests (especially for college applications) – I had to learn that ‘diamond’ IS actually a term used in the US to refer to a baseball pitch!
I am afraid no one bothered to sit down and design proper IQ tests for people from the tropical countries… Just dig some old data from WHO and other organizations/journals and start to speculate.
Bahati M, I agree with you on the HIV/AIDS issue. IQ has little to do with response to the virus.
An economist from University of Chicago, Emily Oster, has written a paper on the issue of HIV/AIDS behavioral response. Her story is that people who face lower life expectancy have no incentive to really protect themselves from HIV/AIDS. Why would a gentleman from rural Malawi have any incentive to procure a condom and protect himself from an HIV/AIDS death in 10 years when something else will kill him in 5 years Her paper can be accessed here: http://faculty.chicagobooth.edu/emily.oster/papers/hivbehavior.pdf
Additionally, another University of Chicago economist and Nobel laureate Gary Becker in his vast literature on Human Capital espouses this exact point that people only make investments in their health when they believe they can live long. If Malaria and other diseases might kill you TODAY, why worry about HIV/AIDS TOMORROW??
Of course, there is some endogeneity in their story because HIV/AIDS is a major factor in pushing down life expectancy in the first place. Or in other words, is it that lower life expectancy reduces incentives to protect oneself from HIV infection or is it that simply HIV reduces life expectancy which in turns increases likelihood of getting infected with HIV.
But I digress, the issue here is that arguing that intelligence, as proxied by IQ, explains why people from tropical climates get infected with HIV is ridiculous.
Another point that seems to cast doubt on their findings is the question of why they left out South America. The reason is clear that the findings from that continent were not consistent with their hypothesis. Or in other words, two things could have happened in the S. America results: Either 1. people afflicted with tropical diseases in S. America, on average, scored HIGHER than expected on the IQ tests or 2. people NOT afflicted with tropical diseases in S. America, on average, scored LOWER than expected on the IQ tests. For the sake of South American pride, let us hope it is the former rather than the latter, for it would mean that S. Americans are really unintelligent.
Otherwise, to be fair, the paper’s assertions makes sense. Although, a more socially acceptable hypothesis would argue that kids who get sick can’t go to school (and hence learn) or other reasons as to why a kid who gets sick might under perform his/her peers who do not get sick.
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