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Comment by bjoli | Hacker News Reader

What we can say about iq tests is that they test something, and those results remain consistent through life. The results are positively correlated to many things (such as academic success. The people scoring a 9, the maximum result, on the tests used in the Swedish conscription live longer, etc...).

Had it been completely pop-pseudoscience it would not be used by, say, the Swedish school system as a tool to gauge whether someone has special needs that warrant another form of school with extra support. The tests used are however not the same as most people have done online, like WAIS (but for kids. Can't remember the name of it).

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> The results are positively correlated to many things (such as academic success.

They would be so correlated even if they were a bad metric. Imagine a score that multiplies academic success and the highest Tetris score obtained within 100 miles of your birthplace, then subtracts 50 points if you're a girl. That would also be positively correlated with academic success.

IQ tests measure something, yes, but they're not magic. (See also: https://en.wikipedia.org/wiki/Goodhart%27s_law) I received a high-quality education including what amounts to IQ-test tuition (to pass an entrance exam); do you know of any studies that attempt to factor out this particular confounder?

IQ tests measure the g factor and also happen to be the best way to measure it. So those opposed to IQ should either come up with a better way to measure g or be open about their rejection of the existence of differences in cognitive abilities.

There's a pretty obvious false dichotomy between "rejection of the existence of differences in cognitive abilities" and assumption that such differences are as shallow as a single factor called g stably related to scores on a collection of pattern recognition tests.

If the best way we have to measure something is very bad, perhaps it's best to say we just can't measure it and keep looking, rather than using a very bad measure. It's like instead of trying to invent scales, we kept trying to measure objects' mass by their volume, which happens to work decently for many common objects, bud fails spectacularly for others. And instead of admitting we just can't measure mass, we'd fill our bags based on volume, and be consistently annoyed when we found we can pick up the "heavier" bag of balloons, but can't pick up the "lighter" bag of bowling balls.

Don't you first have to define what you want to measure and demonstrate that it exists?

Only if you're doing science. It's possible to find things out without science slowing you down, but I wouldn't ordinarily recommend it; science is a great way to avoid the common traps that humans invariably fall into when they try to bypass the scientific method.

> IQ tests measure the g factor

Ah, yes. The g factor: “that which is measured by IQ tests”.

The main arguments for IQ tests, as far as I understand, that they correlate with an assortment of cognitive metrics, which all correlate with each other. This is a question. “It's the g factor” is not an answer; you've just stuck a circularly-defined label on the question (or, rather, on a particular frequentist analysis of the question) and declared it solved.

The best evidence for the existence of the g factor are IQ tests, and IQ tests are optimized to measure the g factor.

Do you see a problem there?

The g factor—or more descriptively—the theory of general intelligence has little support outside of the field of psychometrics. And the field of psychometrics is not known for it’s scientific rigor. Needless to say, there is little reason to believe that the theory of general intelligence has any grounds in reality, nor that the g factor exists outside of an operationally defined concept that might not hold any descriptive power for human behavior outside of a narrow setting of pen and paper tests.

Raw IQ scores aren’t very stable over time. At 90+ peoples raw scores have dropped significantly vs age 30. Trauma, Alcoholism, and other diseases can also lower scores dramatically. You can correlate adult IQ’s with tests taken by 2 year olds, but the individual raw scores again vary significantly.

It seems stable because of how age is adjusting for and the huge sweet spot where 64.2% of the population is grouped between 85 and 115. Basically people with significant developmental disabilities at 5 don’t suddenly become normal, but an IQ of 180 at 5 isn’t stable long term.

At quantum scale or near the speed of light newtonian mechanics breaks down, so we know it a local approximation. However, for set circumstances it approximates it does it well. For many decades physists searched universally true theory to no avail.

My point is this, IQ seems to have signal. It probably doesn't hold up in extreme circumstances. Psychology in particular seems to have a difficult time holding large enough studies to find universal constants that we should accept that IQ might be the best local approxination for now.

That doesn’t support your original point. Color blindness is very persistent over time IQ isn’t. Sure +/- 7 IQ points sounds very accurate, but that can be more than a 30 percentile change from two different tests 1 month apart meaning the actual signal is very weak.

You can read papers saying IQ texts on 2 year olds are strongly correlated with adult IQ, but read the details and individual people’s scores varied wildly.

So sure in aggregate it seems consistent, but that’s largely an artifact of test design. Someone with mental handicaps so profound as to be non communicative will consistently score very low, it doesn’t mean much for the general population.

First of all, scores are normalized to age (you never compare 90 to 30 years olds. Only 90 to 90-ish year olds).

No serious IQ test claim to measure much more than 2 standard deviations up and down (meaning they all break down somewhere above 130-135 or below 70). I have done WISC/WAIS three times (as a part of a psychological assessment) and the conversion to IQ scores were within 3 points (the WAIS/WISC scale measures many different abilities, and can be converted to an "aggregate" IQ score). I asked about this and when people are healthy the tester said people tend to score very similarly on tests, even many years apart.

Yes, the score is computed relative to other 90 year olds, however people’s individual cognitive decline is heavily influenced by heath and behavior so individuals can move up or down significantly on a that relative scale. Thus the computed score at 3 doesn’t accurately predict someone’s score at 90 nearly as well as a test taken at 30 predicts someone’s score at 40.

The issue with the underlying raw score at 90+ is it doesn’t map very well to a bell curve. Many people are quite healthy but a significant number are drastically reduced from their younger self.

My high school transcripts show the results of IQ tests taken in the 4th and 6th grade. Between those two tests, my IQ had dropped by 10%.

What test was it? I have only taken one test (WAIS and WISC, which are more or less the same but for adults and children respectively). It takes about 1 to 1.5 hours and is done alone with the psychologist that administers it.

"as a tool to gauge whether someone has special needs that warrant another form of school with extra support"

Someone is using IQ tests for their intended purpose?!

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