[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.