I live in a country where (to the best of my research) IQ testing for hiring is legal. I wouldn't ever hire somebody on an entry level job without an IQ test again - it's just too useful as a predictive tool. This being said:

• I only used it as a primary rough filter to exclude candidates (ie >110 for a challenging marketing job, which is less than an SD)
• didn't take one myself. Thought about it, just don't see the benefit
• wouldn't dream of doing that for a freelancer, contracter and generally anybody that actually has a trail to look at. It's not only offensive, but useless: no point in trying to measure potential when it's actualised and in front of you

I haven't taken an IQ test myself, and tend to agree with Scott Alexander's Against Individual IQ Worries:

I want to clarify: IQ is very useful and powerful for research purposes. It’s not nearly as interesting for you personally.

How can this be?

Consider something like income inequality: kids from rich families are at an advantage in life; kids from poor families are at a disadvantage.

From a research point of view, it’s really important to understand this is true. A scientific establishment in denial that having wealthy parents gave you a leg up in life would be an intellectual disgrace. Knowing that wealth runs in families is vital for even a minimal understanding of society, and anybody forced to deny that for political reasons would end up so hopelessly confused that they might as well just give up on having a coherent world-view.

From an personal point of view, coming from a poor family probably isn’t great but shouldn’t be infinitely discouraging. It doesn’t suggest that some kid should think to herself “I come from a family that only makes $30,000 per year, guess that means I’m doomed to be a failure forever, might as well not even try”. A poor kid is certainly at a disadvantage relative to a rich kid, but probably she knew that already long before any scientist came around to tell her. If she took the scientific study of intergenerational income transmission as something more official and final than her general sense that life was hard – if she obsessively recorded every raise and bonus her parents got on the grounds that it determined her own hope for the future – she would be giving the science more weight than it deserves.

So to the people who write me heartfelt letters complaining about their low IQs, I want to make two important points. First, we’re not that good at measuring individual IQs. Second, individual IQs aren’t that good at predicting things.

The value and risk are idiosyncratic - they'll vary greatly based on your personality and interaction of your beliefs with the results.

Generally, there's value in quantifying what you already suspect. And there's value in getting another data point into the statistical analysis of the tests. But over-focus on a number when you don't really internalize what it means (and more importantly doesn't mean) can be distracting or demoralizing.

For most people, the standardized testing they've already taken is sufficient - SATs track pretty closely, certainly good enough for most decisions you'd make based on a formal IQ test. Which leaves this in the entertainment category.

To determine if you'd find it worthwhile, write up a paragraph or two about how you'd react for various result bands. I predict that you'll get most of the value from that writeup, and actually taking the test won't matter.

In general, knowing more is better than knowing less. However, if you already believe things that are false, sometimes an additional true information makes you believe more false things. Specifically, if you (falsely) believe that certain values of IQ imply X, Y, Z, then learning your (true) IQ would make you (falsely) believe X, Y, Z about yourself.

IQ is an important trait, but there are also other important traits, and various mental conditions. People who learn about their IQ often make the mistake of trying to explain everything about themselves by their IQ, even if more likely explanations are available. (For example, it is tempting to believe things like "I have a problem connecting with people, but that's because my IQ is higher than theirs" when it's actually lack of social skills; or "I feel bad, because my IQ is so high that I can see many bad things in this world" when it's actually depression.) The life outcomes also depend on environment, and luck.

On the other hand, underestimating IQ also leads to false beliefs about the world. For example, after observing that some (high-IQ) children have great results at school, while other (low-IQ) children have bad results, an IQ denialist would have to invent an alternative explanation; for example, they could believe that the former are hard-working and the latter are lazy, or that the former have some unfair advantage (other than the IQ), depending on their sympathies.

Another problem is that even if you won't take the test, you probably already have some beliefs about your intelligence. Those may be accurate, or not. Maybe you just got [un]lucky. Maybe the feedback you got reflects the prejudice of your parents and teachers more than your actual traits. I don't see an advantage of keeping a (potentially wrong) belief, instead of taking the test. There is nothing you can do about your IQ, so maybe it is better to focus your attention on things you can change. But taking one test should not prevent you from doing that.

With regards to rationality, both high-IQ and low-IQ people can be pretty irrational, albeit in different ways. Smart people can invent really complicated excuses for doing the wrong thing.

Why take a personality test? It gives you insight into your own strengths and weaknesses. It can help you relate to other people. IQ is like that.

The real test result isn't a single number. IQ is a composite score of subtests. If you have an unusually high ability or a deficit relative to your composite score, that could be a good thing to understand about yourself. You'd know what weaknesses to compensate for, and you'd better understand your comparative advantage relative to the average human (and this would still be true if your IQ turned out to be low, which seems unlikely if you like LessWrong).

A baseline may help your doctor diagnose dementia early, which may help with treatment.

Mensa requires you to prove that you have an IQ score in the 98th percentile to join. They have perks exclusive to members. There are other similar high-IQ societies. There are dating sites that cater to high-IQ people and require your score. Intelligent people get benefits from hanging out with people at or just above their level. Your friends rub off on you. (But IQ is not the only way to find intelligent people. LessWrong also has meetups.)

There are two kinds of intelligence: fluid and crystallized. It takes a surprising amount of compute to match expert knowledge. Early AI researchers thought beating humans at chess would be easy. It wasn't. Deep Blue was a supercomputer at the time. Later, better algorithms could reliably beat Deep Blue even when run on inferior hardware. Most of the time, it's the crystallized intelligence that counts.

Those with high IQ tend to acquire more knowledge than average over time; fluid IQ is a major factor in how quickly you learn. It's not the only factor.

A low score may inspire you to dedicate the extra time and effort required to grow your knowledge. Most of the time, crystallized is what counts. If you're dedicated, driven, and/or disciplined, you can out-study a more intelligent person who isn't. It can be a great relief to understand that you're not under-performing your peers due to laziness or some moral failing. It's not your fault. Or you may take it the wrong way and suppose that a low IQ means you must have low self-worth. Don't think like that. You can have compassion for all imperfect human beings (all human beings are imperfect beings), starting with yourself.

A high score may inspire you to try to live up to your potential. It may give you the confidence to acquire useful skills beyond the reach of the average person (higher math, for example). Or you may take it the wrong way and recoil from the specter of expectations you're not motivated to meet. You will never come up against a greater adversary than your own potential.

Do you want to hide your head in the sand, or do you want an accurate map? (Ignorance is bliss!) The truth is not something to be afraid of! Get tested.

IQ is not the same thing as rationality. Keith Stanovich discusses this at length in What Intelligence Tests Miss: The Psychology of Rational Thought. Intelligence can be used to defeat itself. More brainpower means more excuses and more and cleverer ways to shoot yourself in the foot. Learn to stop doing that.

I don’t see a reason to. If you’re wondering “am I smart enough to do X,” there are probably more targeted ways to assess your skill in X.

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