Correlation versus causation, in a graph

We’ve mentioned the relationship between ice cream and murders before, but here’s another correlation example.  Internet Explorer drives people to murderous rages!


Source: Chris Blattman (click to visit his site)

To the often misinterpreted data of correlation, I’ll add another form of misleading evidence often found on the Internet: the personal anecdote.  I haven’t used Internet Explorer in almost a decade, and I haven’t gone on a single homicidal rampage in that time.  It must be true!

Roundup on race and IQ

Jason Richwine’s 2009 Harvard dissertation IQ and Immigration Policy has been all over the news for the past few days, after the circulation of a controversial Heritage Foundation report on immigration with which he was involved.  A lot of thoughtful people have written on the topic and provided a better analysis than I can in a short blog post. So instead, I’ve collected a reference list of a dozen links for anyone who wants to read more. I’m trying to focus on articles that discuss the science and philosophy of the issue, not politics or whether his dissertation was properly reviewed.

  • Heritage study co-author opposed letting in immigrants with low IQs from The Washington Post. This article seems to have been the spark that lit the fire of this controversy.  “Toward the end of the thesis, Richwine writes that though he believes racial differences in IQ to be real and persistent, one need not agree with that to accept his case for basing immigration on IQ. Rather than excluding what he judges to be low-IQ races, we can just test each individual’s IQ and exclude those with low scores.”
  • What We Mean When We Say ‘Race Is a Social Construct’ from The Atlantic. “When the liberal says ‘race is a social construct,’ he is not being a soft-headed dolt; he is speaking an historical truth.”
  • Why People Keep Misunderstanding the ‘Connection’ Between Race and IQ also from The Atlantic. “Among rich kids, good opportunities for developing the relevant cognitive skills are plentiful, so IQ differences are driven primarily by genetic factors. For less advantaged kids, though, test scores say more about the environmental deficits they face than they do about native ability.”
  • Two from the American Anthropological Association: RACE – Are We So Different? and the 1998 AAA Statement on “Race”  “At the end of the 20th century, we now understand that human cultural behavior is learned, conditioned into infants beginning at birth, and always subject to modification. No human is born with a built-in culture or language. Our temperaments, dispositions, and personalities, regardless of genetic propensities, are developed within sets of meanings and values that we call ‘culture.'”
  • Race And IQ. Again. on Andrew Sullivan’s The Dish. “But please don’t say truly stupid things like race has no biological element to it or that there is no data on racial differences in IQ (even though those differences are mild compared with overwhelming similarity). Denying empirical reality is not a good thing in any circumstance.”
  • Six Reasons Why Race-and-IQ Scholarship is an Intellectual Dead End from, largely a response to Sullivan [via @savageminds] “Let’s say it were discovered that one American racial group was, once all the effects of nutrition, healthcare, education, income, parenting, and every other environmental factor were controlled for, on average innately slightly less intelligent than another. Would that finding justify discriminating against the less intelligent group in employment, education, or any other realm of endeavor?”
  • Should Research on Race and IQ be Banned? from the Scientific American Cross-Check blog.  “Irony Alert: It just occurred to me that two recent films, The Great Gatsby and Django Unchained, feature villains who spout pseudo-scientific theories of white superiority. The films imply that these theories are ludicrous relics of our racist past and that no modern person could possibly believe them. If only.”
  • The IQ Test from Slate. “’I have never worked on anything even remotely related to IQ, so don’t really know what to think about the relation between IQ, immigration, etc,’ Borjas told me in an email. ‘In fact, as I know I told Jason early on since I’ve long believed this, I don’t find the IQ academic work all that interesting. Economic outcomes and IQ are only weakly related, and IQ only measures one kind of ability.'”
  • Flynn, Ceci, and Turkheimer on Race and Intelligence: Opening Moves from Cato Unbound (2007). Don’t miss the links to response essays at the bottom of this article. “Take, for example, health care. Patients differ enormously in intelligence level, and these differences have life and death consequences for them. Individuals of lower health literacy, or IQ, are less likely to seek preventive care even when it is free, use curative care effectively when they get it, understand and adhere to treatment regimens, or avoid health-damaging behavior.”
  • A Talk with Jason Richwine from The (Washington) Examiner.  (speaking about making an even more controversial statement in a 2008 panel) “What I emphasized was that ethnic group differences in IQ are scientifically uncontroversial. That being said, there is a nuance that goes along with that: the extent to which IQ scores actually reflect intelligence, the fact that it reflects averages and there is a lot of overlap in any population, and that IQ scores say absolutely nothing about the causes of the differences — environmental, genetic, or some combination of those things.”
  • And finally, a 2009 Guardian review of Stephen Jay Gould’s The Mismeasure of Man. “This book should make any sensible person wary of attaching too much value to IQ tests (there’s some glorious stuff on the quixotic allotment of IQ ratings) and should make anybody very suspicious of statements about ‘group IQ’ or the presumption that some races are innately more clever than others.”

Mash Season 9 Episode 16: The Red/White Blues

Alternate, in case that link has issues:

(Both are gorilla but 2 separate uploads)

Start at 7:11 to play; if you have time, watch until the end as a health note finishes the episode. (Each episode is only about 23-25 minutes long) In this episode Springtime has come in Korea which means malaria. Unfortunately not everyone can take the medicine…for reasons you’ll have to see.

Still slightly confused about the outcome of the video? A medication that reacts poorly to people and communities of African and Mediterranean decent? Primaquine was created in 1946, it was tested during WWII on volunteers, soldiers, and prisoners of war. It was seen early on that those who were African-American had a hemolytic reaction to the medication, (though it was also noted there there were a few cases of Caucasion reactions also). After that doctors were given the warning not to use Primaquine or only in sparing amounts in those of African decent. It became a ‘race warning’, later by the time of the Korean war those who had Mediterranean background were included and recently those in the Middle East (Iraq and Iran) have been added to the list…. But is it a race issue? In fact it is not, what the Primaquine is reacting to is an allele called Glucose-6-Phosphate Dehydrogenase. Those with the allele have a hemolytic reaction when they use Primaquine. To make it very clear…. EVERYONE has the ability to have this allele. So why does it appear to create a race affect visually in those that have a shared community background for lineage or decent? Those who read my previous post may know where this is going…. that’s right! Cross-Protection! James V. Neel explains it in his article Are Genetic Factors Involved in Racial and Ethnic Differences in Late-Life Health?

‘The sickling alleles and the G-6-PD deficiency alleles are representatives of balanced polymorphisms. Homozygosity for the hemoglobin S allele is usually inconsistent with reproduction because the homozygotes usually die in childhood. Homozygosity for a G-6-PD deficiency allele (or hemizygosity in the case of a male) by no means confers the handicap of sickle cell anemia but must still be regarded as impairing the fitness of the homozygote. But in both cases, the alleles have a positive side, conferring resistance to malaria, and the frequency of the allele in a population is determined by a balance between positive and negative selective forces.’

Translation? Environment, environment, environment! This allele provides a protection against Malaria. So those in a community that have the allele and Malaria in their environment will see an upsurge of the allele in procreated generations because those without the allele may not to survive as well without the added protection. Non-alleles will be less likely to procreate a new generation when dead from the extra benefit of protection.  When more members of a community, line of decent, or group heritage have an allele it can make it appear that their ‘race’ may be more or less susceptible then others to things, when in fact this is a result of environment messing with allele spikes. Nor does it matter that the allele itself may be what causes a separate disease or condition. Its protection might be an unintentional side effect of the primary disease or condition or a protection mechanism against other diseases wiping out the primary disease or condition. So the appearance that Primaquine is not advised in certain ‘races’ is deceptive. The health label has since been changed to read that it is not advised in those with the Glucose-6-Phosphate Dehydrogenase allele else wise hemolytic shock may occur or those with similar conditions. For a long time though it was treated as a race issue from the naked eye when in truth the culprit was microscopic…. but universal.

Additional Readings…

Who are the weird?

There’s a fascinating article making the rounds of various blogs this week, which does a nice job of summarizing the interesting findings of a young group of psychologists looking at cross-cultural variation in a series of games and perceptual tests that have long been assumed to measure universal human qualities.  Over and over again, they are finding that Western subjects respond in very different ways than most people to these kinds of tests; in fact, Western subjects are outliers, even though the vast majority of our data on human behavior and psychology (96% of psychology studies) is limited to the study of Western populations.

This is not exactly news to most anthropologists (or to anyone; the paper the article is discussing came out a few years ago and was widely discussed then as well), but the article does not let the discipline off the hook, accusing the anthropological stance on cultural diversity of being incoherent in that we want to maintain two incompatible claims.  On the one hand, anthropologists extol cultural relativism as a basic principle, emphasizing that cultural differences are real and significant and need to be respected.  On the other, undergraduates come away from an anthropology class with the sense that we are also all underlyingly the same.

This strikes me as a fair critique to a limited extent, but the quandary of the anthropologist is less severe than that of those social sciences (psychology, economics) that want to assert the existence of an analytically accessible mind underlying and separable from cultural variables.  I think many of these kinds of social scientists will come away from the article shaken, but not despairing; maybe, they will reason, you have to try for cross-cultural representativeness for things like game theory, but surely not for things further along the biological end of the biocultural spectrum.  And yet we know from our course readings that this is not true either: we have seen that what seem like very biological processes, from so-called African “precocity” (Gottlieb) to “normal” menstruation patterns (Strassmann), are very different for most of the world than for the Westerners who have long been presumed to be typical.

The always incisive neuroanthropology blog has done a great job of giving an overview of the review article, as well as pointing out some of the problems inherent in the neologism WEIRD (Western, Educated, Industrialized, Rich, and Democratic), despite its catchiness.

On ice cream, lead, and murder

On this blog in the past, we have looked at some intriguing ways in which social issues such as violence may be considered as epidemics.  We have also looked at some of the problems in public health with confusing correlation with causation; a classic statement of the fallacy is often given as follows: in summer ice cream sales go up, and murder rates go up.  Therefore, eating ice cream causes murder.

The example of ice cream and murder is absurd, but it points out just how difficult it can be to ascribe causation definitively in matters of public health.  Clearly, both ice cream sales and murder rates are independently affected by the same actual cause (heat waves), but one could easily imagine compelling data showing that ice cream sales go up just before each wave of violence.  And in fact, a fascinating new piece in Mother Jones has been getting a lot of attention in public health circles this week because it shows exactly that kind of compelling relationship between violence and a different factor: leaded gasoline.

Through a pretty careful analysis of past publication, the article makes an extraordinary claim: “Gasoline lead may explain as much as 90 percent of the rise and fall of violent crime over the past half century”.  But it has the data to back it up, and what’s really intriguing is that these correlations hold from the macro- all the way down to the neighborhood level.  In neighborhoods where lead is removed, crime rates drop a predictable number of years afterward.  If there really is a causal relationship between lead exposure and violent crime, we should be making the removal of lead from the environment a top priority- and maybe we should also be reconsidering the effectiveness of the police campaigns that are claiming the credit for the tremendous decline in violent crime America has been experiencing in recent decades.

But is this really ice cream and murder all over again? Scott Firestone has an excellent blog post about the MJ piece that does a nice job discussing why we might temper our enthusiasm about these findings somewhat (although he also finds the data very compelling), and it’s worth reading just to think more about how hard it can be to prove anything with certainty, even when the evidence is extraordinary (think of how successful tobacco lobbyists were for so long in creatively interpreting the data on the health effects of smoking).  There’s a brief and well-executed discussion this week in Scientific American about just how hard it can be to establish causation in health on another issue:  whether even very moderate amounts of drinking during pregnancy has any negative effects on babies.  This should be easy to establish, but it isn’t: in part because of ethical considerations (you can’t set up a control for potentially harmful behavior), in part because of the reliability of self-reports, and in part because of confounding variables like “lifestyle” associations (the same arguments tobacco lobbies make).

Micah posted this in March, with the comment, “Do hair relaxers cause uterine fibroids in African-American women? Sounds like ice cream and murder to me.”

This author agrees: Chemical relaxers linked to high uterine fibroid risk in African-American women? I doubt it.