What are the advantages and disadvantages of knowing your own IQ?

Eh. It's hard for me to argue that knowing the truth of something is a bad thing. The harm comes from believing falsehoods. Knowing the results of one or more IQ tests can be true (you did in fact get that score on that test) and helpful.
Believing that the number on the test is identical to your actual IQ, or that IQ by itself means very much, is incorrect and harmful.

It can help (if high) in inspiring you to study and think about more difficult topics. It can help (high or not) by reminding you that you need to work harder than some on difficult topics. It can help in helping you figure out what personality strengths to develop that complement your pure cognitive strengths. It can help in reminding you that there is _always_ someone smarter, and that most of the time that difference is overrated.

It can harm by forgetting that it's a very imperfect measure, if it makes you feel superior or if it causes you to dismiss others' ideas and opinions. Or if it demotivates you, or makes you think you can't approach difficult topics.

It looks generally redundant in most cases to me: Given how pervasive IQ-correlations are, I think most people can get a reasonable estimate of their IQ by observing their life history so far. E.g.

• Educational achievement
• Performance on other standardised tests
• Job type and professional success
• Peer esteem/reputation

Obviously, none of these are perfect signals, but I think taking them together usually gives a reasonable steer to a credible range not dramatically larger than test-restest correlations of an IQ test. An IQ test would still provide additional information, but I'm not sure there are many instances where (say) knowing the answer in a 5 point band versus a 10 point band is that important.

The case where I think it could be worthwhile is for those whose life history hasn't generated the usual signals to review: maybe one was initially homeschooled and became seriously ill before starting employment/university, etc.

People seem to treat it in a fatalistic way, like they’ve been told what their score will be at the end of the game, as opposed to one of their base stats (like finding out how tall you are). I tested myself on the big 5 lately and finding out I have a fairly extreme baseline on things like neuroticism and intellect been surprisingly valuable for understanding myself.

I understand there are also subcategories of IQ, and I am interested to know if there’s an IQ test I can take which gives me info on a variety of the more robust components of IQ (whatever they are, I don’t actually know). I could imagine this giving me advice of the type “In general try strongly to use verbal reasoning over spacial reasoning, and if you’re in a situation where spacial reasoning is necessary, make a conscious plan to put in more deliberate practice than seems necessary for the median similarly smart person around you who is learning the same skill.” If I expected to get 3+ big recommendations like that I think I’d be quite excited to pay for a test.

I think that having IQ tie more closer to your decisions might help people understand it than if it’s just an abstract immutable number that says you’re worse than these other people, and having it be multifactorial could be a way to help there?

But unless I can actually tie it to some decisions, I do expect finding out my IQ to make me depressed on net. Perhaps I can just use it to figure out whether or not it’s on the table for me to do math at MIRI, though my sense is that philosophical sophistication is much more the bottleneck there.

IQ tests are not designed to be resistant to training effects. I don't think they are a good tool for tracking neurodegenerative dieseases as they are not optimized for that purpose.

Given existing tools I would rather use QuantifiedMind.

If someone wants to spend more time I think it should be possible to analyse Anki data for good metrics.

Individually, IQ is a metric that tells you how you compare to other people and that can be useful to get a better understanding how other minds differ from your own.

I think that people treat IQ as giving more information than it actually does. The main disadvantage is that you will over-adjust for any information you receive.

An advantage I have found of knowing my IQ is that I can consider the normal distribution of IQ scores and determine roughly how many people are smarter than I am in a given population (such as the city I live in, or the surrounding metropolitan area). In particular, it helps me to understand why I'm typically the smartest person in any particular group I participate in, but also reminds me that there are a large number of people smarter than I am within convenient travel distance, despite our social circles not obviously overlapping.

IQ is measuring something real and important to life outcomes (the so-called g factor) but it is not everything that matters to life outcomes or cognition. As Keith Stanovich pointed out in What Intelligence Tests Miss, IQ is not the same thing as rationality. Your intelligence can defeat itself if misapplied. And due to human nature, it will. The more clever you are, the more ways you can deceive yourself. Reading the Sequences (or RAZ) can help you learn to stop doing that.

Why wouldn't you want to know your own IQ? Are you afraid a "bad" result would become a self-fulfilling prophecy? If you want to be more rational, then the truth is not something to be afraid of! You have been living your whole life with whatever IQ you have. Knowing your own strengths and weaknesses doesn't change what they are. It just gets rid of the weakness of not knowing that.

There are multiple components to IQ tests. You may be stronger in some areas than others. In my case, the IQ test revealed that I have a learning disability, despite having the overall genius IQ typical of LessWrong readers (or at least LessWrong survey takers).

Learning about this was not a disappointment. It was a relief. I had always felt like I somehow wasn't measuring up to my own apparent potential, but now I realize it wasn't my fault. Now that I know what my weakness is, I can better compensate for it, and better leverage what strengths I have.

While we don't know good ways to improve fluid intelligence by much (besides avoiding those things that make it worse, like sleep deprivation, etc.) there are well-known ways of increasing your crystallized intelligence: Read more and better books. Listen to audiobooks during your commute. Use SRS and mnemonics. Specialize. You can generally out-learn someone a bit smarter than you if you develop better study habits. And you can expect to far out-learn someone who isn't even studying your field.

You can also increase your effective fluid intelligence in many useful situations by using external tools. Working memory is consistently one of the worst bottlenecks in human cognition. Write things down when thinking. Draw diagrams. Take pictures.

Learn to use a computer more effectively. Try org-mode or FreeMind or TiddlyWiki. Learn to use a spreadsheet. Try AutoHotKey to improve your efficiency. Learn Python, if you can. Try working through a math book with Mathematica instead of pencil-and-paper. There's a night-and-day difference in effectiveness between an illiterate genius and a merely bright person who has access to a PC and Google and knows how to use them.

What would you gain from knowing your own IQ?

As far as I can tell, knowing my own IQ is a no-win scenario. Either my IQ is higher than I expected it to be, in which case I feel like I'm a disappointment, or it's lower than I expect it to be, in which case I'd feel like a fraud. I wouldn't gain any actionable data from it, so why bother?

IQ doesn't actually mean much. Stephen Jay Gould's The Mismeasure of Man is a good place to start. IQ varies wildly based off socioeconomic status, education, age, amount of sleep, whether or not you've had any stimulants/depressants/any mind-altering substance, how much you've had to eat, if you've mentally or physically exerted yourself, and so on.

Tracking IQ within an individual could be useful as part of a battery of other tests to predict cognitive degeneration, but a decrease in IQ could simply mean you're having a bad day.

Additionally, intelligence is genetically variable, not genetically determined. It has much to do with environmental, social, and cultural factors, enough to make the genetic component not very important. That means that it's always possible to increase-- through education, practice, etc.-- your IQ, just as it's possible to decrease it-- through drugs, disuse, dogmatization and false beliefs, and so on.