[cltby]

Question for any IQ skeptics here (e.g. "it just measures your ability to take tests" or "it just tells you how rich your parents are"): what's your response to studies like this? Is there anything that can be said about the effect of lead on cognitive function? Why might IQ be a good measure of lead-induced stupidification, but unreliable for literally anything else?

[omginternets]

I think it's a pretty straightforward thing: intelligence somewhat correlates with life/career outcomes overall, and it's not linear. Separately, IQ tests are reasonably good, though imperfect measures of general intelligence. Also separately, if you look at careers where high intelligence is needed, then IQ correlates much better.

IQ does not principally measure test-taking abilities or SES. Yes, those correlations exist, but their effect sizes are not nearly as large as a certain political ideologies would have you believe. And simultaneously, it's not as ironclad as the other political ideology would have you believe. It's very reliable as these things go, but noisy at the margin.

EDIT: a sibling comment correctly points out that aggregate effects do not always apply individuals.

[masfuerte]

It's possible for IQ to be a good population measure while being a poor individual measure. (FWIW, I think proponents and opponents of IQ testing all overstate their cases.)

[hedora]

I assume the study authors controlled for such things. For example, they could bin the study participants by socioeconomic group, race, location, etc, etc, etc, and then show the average IQ loss per bin.

I haven't read the study, but statisticians do this stuff for a living, and there are definitely ways to control for sample biases that let you distinguish between "poorer people have lower IQs and are exposed to more lead, and the root cause of both is being poor", and "lead leads to lower IQs within all socioeconomic groups we could think of and measure"

[cltby]

But these controls could be done for any IQ-related study. Is IQ-skepticism based on the belief that IQ researchers generally don't use controls? That lead-IQ researchers alone do this?

[astrange]

You can't demonstrate causation by controlling for things, because of collider bias.

https://en.wikipedia.org/wiki/Bad_control

You need better methods like an intervention study or a natural experiment to show causation.

[mkoubaa]

Most IQ skeptics think IQ correlates with intelligence. The argument is generally over how good a proxy it is for intelligence and what conclusions can and can't be drawn from statements about IQ

[harry8]

False.

Low IQ correlates with lack of intelligence. Average and above means nothing.

--IQ skeptic

[mkoubaa]

That's still a loose correlation, but I do appreciate the correction

[harry8]

Intelligence is both directions. It only correlates with un-intelligence. Eg the poor individual has a brain injury or does not.

[raincole]

If the chemical can complete nullify the advantages of having rich parents, how doesn't it sound bad enough...?

[astrange]

You have to read the study to find out what it meant by IQ. People freely confuse IQ (a score on a test that's calling itself an IQ test) with IQ (a platonic ideal statistic people assume exists for the purpose of publishing research about it). This could be either.

[cltby]

Sorry, is your criticism that IQ proponents conflate point estimates with unknown population parameters? Is that what other IQ critics see as the core of the disagreement in this debate?

[astrange]

Well I don't want to speak for anyone else.

It's more of a secondary criticism though, that people aren't very careful about reading research papers. And of course that in many fields the researchers aren't careful either (https://en.wikipedia.org/wiki/Credibility_revolution).

The primary criticism is that people want there to be something called IQ (or g, or intelligence) that is 1. a real physical variable that causes things 2. an unchangeable attribute of a person that 3. makes you better and more virtuous than people with less of it. This recently causes 4. the belief that if we invented an AI it'd have a lot more of it than us and would take over the world[0].

Whereas I think that:

1. the best reason to know it is to find working interventions to improve it, which they can't find because it isn't real, so they should find some real physical processes.

2. the other reason to know it is to predict someone's ability on a task, and in any such situation there is better evidence you could use for that. Although this one's kinda illegal anyway (https://en.wikipedia.org/wiki/Griggs_v._Duke_Power_Co.).

3. a superintelligent computer would not take over the world.

[0] The Lesswrong guy, the main advocate of this one, didn't graduate high school but would like to be seen as intelligent, which means it's convenient to believe that intelligence is so inherent you don't have to prove it by performing well at school.

[dragonwriter]

No, IQ is just the test result; the theoretical phenomena understood to be underlying it are things like g and task-specific factors.

[astrange]

You're claiming this study used a test that it could have a "the test result" for, but it didn't - it's a meta analysis using another meta analysis, whose different studies all used different tests:

https://www.thelancet.com/journals/lanplh/article/PIIS2542-5... <- the one in the article

https://ehp.niehs.nih.gov/doi/10.1289/ehp.7688 <- the one it refers to

> We contacted investigators for all eight prospective lead cohorts that were initiated before 1995, and we were able to retrieve data sets and collaboration from seven. The participating sites were Boston (Bellinger et al. 1992); Cincinnati (Dietrich et al. 1993) and Cleveland, Ohio (Ernhart et al. 1989); Mexico City, Mexico (Schnaas et al. 2000); Port Pirie, Australia (Baghurst et al. 1992); Rochester, New York (Canfield et al. 2003); and Yugoslavia (Wasserman et al. 1997).

I checked two of the studies from 1989:

https://www.sciencedirect.com/science/article/abs/pii/089203...

> The test used was the Wechsler Preschool and Primary Scale of Intelligence.

https://www.nejm.org/doi/full/10.1056/NEJMoa022848

> We measured blood lead concentrations in 172 children at 6, 12, 18, 24, 36, 48, and 60 months of age and administered the Stanford–Binet Intelligence Scale at the ages of 3 and 5 years.

So they didn't all take the same test[0]. This supports my claim, which is that people who believe IQ research also believe that all test results produce the same valid statistic called IQ as long as the test calls itself an IQ test.

I actually can't think of a time I've seen an online IQ arguer claim that any given test result isn't an accurate representation of an IQ. They certainly also think it about things like SAT scores and old national-IQ studies where they gave the tests in second/third languages or just made up the numbers.

[0] if it was the same test, isn't the norm process to convert from raw scores to normally distributed ones be different in different years? Not sure how that part is done.

[swayvil]

I think IQ reflects your general cognitive ability AND a few other things like wealthy parents etc.

Just like your videogame score reflects your diet and a few other things.

Just like lots of things.

[csa]

> "it just measures your ability to take tests"

This is largely wrong. One could be a master at test-taking and not come close to a high score.

That said, familiarly with the test/item structure almost certainly helps, especially for folks with the potential to score high (see below).

> or "it just tells you how rich your parents are")

Hmm… family wealth and IQ may be correlated, but not perfectly so. There are plenty of low-IQ rich people and also plenty of high-IQ poor people.

> what's your response to studies like this?

Probably too many confounding variables. That said, this study is a publishable unit that can push one or more funded agendas, so here we are.

> Is there anything that can be said about the effect of lead on cognitive function?

While I know a bit about IQ, I don’t know much about the details of the relationship of IQ and lead.

> Why might IQ be a good measure of lead-induced stupidification

Maybe it’s not. See “funded agendas” comment above.

> but unreliable for literally anything else?

(the main reason I replied is below)

People really need to let go of this idea in a reasonably reliable way.

1. IQ measures reasoning ability. It is quite good at measuring this.

2. People put a lot of weight onto how IQ correlates with a bunch of other things, but these are not things that IQ tests are designed to measure. As such, these correlations may not be meaningful in some cases. So the “literally anything else” that IQ is allegedly not good for is almost entirely things that IQ tests are not designed to measure. I don’t think it’s prudent to disregard the test/measure because of misuse by some folks (typically within agendas).

3. People get very self-conscious about IQ scores. Let me help with that. IQ scores are a measure on a particular day that can vary from day to day for any one person. For any given test taker, they are trying to optimize what they score out of a theoretical max (i.e., their “true IQ”). Many, many things cause people to score lower than their potential max — lack of sleep, lack of food, external distractions, distress (physical, mental, emotional), anxiety, ambivalence, lack of test familiarity, etc. Very few things cause them to score higher than their max (it will almost certainly be within the confidence interval). It’s ok. Retake the test if it matters (it usually doesn’t).

4. IQ matters most in three areas, imho. The first is at the extremes. Gifted/genius folks and learning disabled folks need additional resources. How and whether this is implemented is highly debated. The second is in leadership positions. You want your leaders (e.g., in the military) to be within about 20 IQ points of those they lead. The idea is that > 20 IQ delta folks see the world in fundamentally different ways, so leading someone who views the world so differently is difficult and largely inefficient. The third is with one’s significant other. Same as above, it will be hard to be understood (if that’s your goal) by someone who is +/-20 IQ points away from you.

I hope this helps.

[gpt5]

Dude, you are spewing out random things as if they are fact. Yet you lack an understanding of what IQ is.

IQ is an attempt to measure a general intelligence factor (g-factor). What happened is that researchers noticed that people who are good at some tests tend to also be good at other tests, even if it's from very different domain. E.g. say you are good with math, you also tend to be good in you language skills. This led to the assumption that there is a general factor out there that is shared across all skills (the g-factor). So determining how good you are at math is a combination of your math specific skills + the g-factor. Same with other domains.

How do you extract the g-factor? You measure a large set of people across a cognitive challenging set of tests, and do a factor analysis (statistical technique) to extract a linear g-factor. Each test can have a "g-loading" which essentially calculates what portion of it is due to the general g-factor. For example, one of the tests with the highest g-load is simply hearing a sequence of numbers and repeating them in reverse. This test has nothing to do with "reasoning skills. Yet for some reason you claim that it's designed to measure reasoning skills but not designed to measure "a bunch of other things".

You also claim that IQ varies significantly day to day, but that has not been shown in studies. In fact, IQ measurements tend to be remarkably stable across the person's entire adult life.

Than you spewed up a bunch of unsubstantiated claims about the difference of IQ between a leader and his team.

[csa]

> Dude, you are spewing out random things as if they are fact. Yet you lack an understanding of what IQ is.

In my previous career, I did quite a bit of research on IQ. I’m pretty sure I have a decent understanding of what it is.

If you take out your straw-mans and overstatements of what I said, then I think you will be able to find research that supports everything I said above about IQ approximately to the degree of confidence that I stated it.

[gpt5]

Let’s make it easy - please cite the research that shows that an IQ gap of 20+ leads to worse leadership results.

[csa]

> Let’s make it easy - please cite the research that shows that an IQ gap of 20+ leads to worse leadership results.

Iirc, Greatness: Who Makes History and Why cites some research on this very topic.

There is more to be found — I’m sure you can find it if you try yourself or ask a librarian at a good academic library.

I will also add that you have conveniently ignored the fact that I prefaced that specific section with “imho”. It’s my opinion, and I stated all of those comments as such because I don’t think that there is any unassailable research in this area. There probably won’t be due to the difficulty of structuring a good and replicable study regarding IQ and IQ deltas specifically.

While the overall research is not air tight, there is research that I have done (unfortunately proprietary) that indicates that the “20 IQ point difference” concept is directionally correct (“directionally” because we had to use IQ proxies). Implementing this in organizational restructuring led to consistent measurable improvements at the extremes (which was our focus).

Given your challenging tone and style of engagement, I’m guessing that you’re hellbent on flaming. I’m not interested. As such, I will leave you to your library and librarian to find research that supports the ideas I have stated (assuming you bother to look).

“Leadership and IQ delta” a super interesting topic, but the current trends in psych research and psych funding unfortunately don’t really focus on these areas despite demand from outside of academia (it’s very political in an uninteresting way).

Best of luck!

[gpt5]

The reality is that it’s very difficult to come by any research that shows that higher IQ leads to worse outcome (which your delta hypothesis claims).

We also know that iq correlated over 0.95 between same person taking the test on a different day, so any claim around daily fluctuation is exaggerated except for outlier cases. Your claims paint a different picture.

[colechristensen]

IQ is a mediocre-at-best metric for intelligence. "Intelligence" is probably real and variable among people, but poorly defined, very hard to test, and subject to a whole lot of opinion.

IQ is bad at comparing people from different backgrounds, especially across cultures, languages, etc.

But IQ can be a valid comparison for a single non-cultural variable. i.e. lead exposure in otherwise identical cohorts.

[cltby]

> otherwise identical cohorts.

You could do this stratification/matching for any IQ study. What's special about lead-IQ?