Wednesday, July 07, 2010

The Disease-IQ Link

We know that infectious disease inflicts many burdens on developing countries -- high infant mortality rates, for instance, and shortened lifespans. But new research highlighted in the Economist this past week indicates that perhaps too many pathogens can result in lower intelligence among the populace, too. You can read the article here.

While controversial, here is the explanation. In young children, a developing brain demands the majority of a body's metabolic energy. Any competition for this energy will result in less energy for the brain at a crucial juncture. Infectious diseases require quite a bit of energy to fight (or result in diarrhea, which prevents the body from absorbing nutrients which would feed the brain). Some practical evidence seems to support this; many children who manage to recover from cerebral malaria suffer cognitive disabilities afterward.

Of course, one has to be careful with all this. For some time, "experts" cautioned that teen girls shouldn't be educated because tending their brains would divert energy from their developing reproductive systems -- a sort of reverse of this hypothesis. But it does appear that the countries with the highest measured average intelligences (like Singapore and South Korea) have the lowest disease burdens. And, of course, this explanation does offer hope for future development. If you eradicate disease, you get a human capital boost apart from the fact that people will be healthier. They may be smarter too.

And as readers of this blog know, intelligence matters. A 150 IQ kid whose intelligence is lost due to disease is an asset a developing country will sorely miss.

5 comments:

hschinske said...

Isn't this just a consequence of the brain being part of the body? I don't see how anyone could possibly be surprised that one's effective level of mental functioning might be altered by acute or chronic disease. Naturally any *particular* individual might do surprisingly well despite disadvantaged health, as Newton overcame being a very premature (for the time), sickly baby, and Ramanujan got through a surprising amount of original math before dying young of TB. But it's not the way to bet.

I have to admit, any time I see the "average IQs" of various countries reported I cringe and suspect horrid motives for reporting the data in that fashion. I bet that's where the "controversy" lies -- not on the idea that disease can do bad things to your brain as well as to the rest of your body.

Bostonian said...

Steve Sailer explains at http://isteve.blogspot.com/2010/07/guardian-lower-iqs-found-in-disease.html that the causality between IQ and disease is probably bi-directional. Disease can reduce IQ, but societies with higher IQ also take measures to reduce disease.

Regarding hschinske's "cringing", whether average intelligence varies by race has many policy implications, such as

(1) the feasibility of NCLB's mandate to eliminate the racial achievement gap

(2) the advisability of an immigration amnesty that would make many Hispanic illegal aliens permanent residents. American Hispanics have been estimated to have IQ's about 10 pts below whites (blacks are 15 pts below).

We shouldn't bury our heads in the sand in order to ignore obvious patterns.

hschinske said...

Bostonian, I suggest you read Stephen Jay Gould's _The Mismeasure of Man_. Intelligence is only very imperfectly summed up in one number even for an individual; why would we think that one number could be a meaningful summing-up for a whole country or a whole racial group? In any case, biologically speaking there is no such thing as race.

If you read any history, you'll see a lot of obvious patterns of so-called "undesirable" immigrants being classed as of low intelligence -- including Jews, Chinese, Russians, Italians, Irish ... the list goes on and on. I see very much the same racism and xenophobia in evidence today. Plus ca change, plus ca la meme damned chose.

hschinske said...

http://blogs.discovermagazine.com/notrocketscience/2010/06/29/does-national-iq-depend-on-parasite-infections-er/ has an interesting take on the article: "this new paper is the latest in a long line of hypothesis-generating publications from Fincher and Thornhill linking parasites and infections to pretty much any sweeping aspect of human life you can think of. Through similar studies based on correlations at the national level, Thornhill and Fincher have suggested that infections are linked to individualism and collectivism, religious diversity, linguistic diversity, armed conflicts and civil war, and democracy and liberal values. Like any attempt to explain very complex patterns of human behaviour through a single cause, this ought to raise an eyebrow. I’m raising two."

Anonymous said...

“Regarding hschinske's "cringing", whether average intelligence varies by race has many policy implications, such as

(1) the feasibility of NCLB's mandate to eliminate the racial achievement gap

(2) the advisability of an immigration amnesty that would make many Hispanic illegal aliens permanent residents. American Hispanics have been estimated to have IQ's about 10 pts below whites (blacks are 15 pts below).”



You keep thinking that while a group of people of color who are able to navigate education politically and are able to circumvent institutional racism continue to grow. I cannot help your ignorance if you decide not to open up your eyes and see.

http://www.nytimes.com/2009/05/08/
opinion/08brooks.html

http://www.forbes.com/2007/05/21/outsourcing-waters-harvard-oped-cx_mcw_0529harvard.html