As I mentioned in this post about things I’ve changed my mind on [1], one of them is IQ. I used to believe that IQ was unimportant or overly simplified. But I’ve since been educated against my prejudice—it is a very successful psychometric [2] and has impressive predictive power.
Still, after accepting the usefulness of a general measurement for intelligence, I still don’t want to know my own value. I’m not sure why, I just get a squicky feeling when I think of reducing my own cognitive ability to a few digits.
Commenter Jay Cross summarizes his feelings [3] against knowing your own IQ as well:
“Regarding IQ: while I fully concede that IQ matters, is predictive, and has value as a scientific concept, I don’t see any benefit to individuals knowing their own.
Seems to me it could only hurt. If it’s higher than you thought, you could become complacent. Lower, and you could get mired in self-doubt.”
I suspect that many (although certainly not all) of my readers share this aversion to taking an IQ test. Since it’s an issue I haven’t convinced myself of yet, instead of my typical stance where I phrase a question for the essay title and then proceed to argue heavily for one viewpoint, I’m going to open up the debate I’ve had with myself both for and against, and ask you to weigh in with your thoughts at the end.
Arguments for Knowing Your Own IQ
IQ is predictive of a wide range of life outcomes: academic achievement, income, productivity, and even whether you’ll commit crimes or not [4]. IQ is also fairly stable and heritable [5]. While the interpretations on that are somewhat murky, it does suggest taking the test isn’t going to give you terrible information about your cognitive ability.
In general, having more knowledge about your ability is important. It can be crucial information to help you decide whether to strive or settle [6], by altering the percentage likelihood of success for certain goals.
If you knew, for instance, that working your hardest at a starting a business, graduating college or becoming a physicist would have an 80% or only 8% chance of success that might change your decision. While taking an IQ test may not give you exact figures, it does give you more information. Theoretically, at least, that should make it easier to make important life decisions.
Consider an analogy: you want to become a professional basketball player. One important piece of stable, heritable information that is very important for that decision is your height. Scott Alexander explains the wild bias towards tallness [7] in basketball in terms of your chances of being in the NBA for a given height:
“34% of the US male population is 5’9 to 6’0, so about 54 million men. There are 5 NBA players in this band. So about one in every 11 million people of this height is in the NBA.
13.5% of the US male population is 6’0 to 6’3, so about 21 million men. There are 40 NBA players in this band. So about one in every 500,000 people of this height is in the NBA.
2.35% of the US male population is 6’3 to 6’6, so about 4 million men. There are 95 NBA players in this band. So about one in every 40,000 people of this height is in the NBA.
0.15% of the US male population is 6’6 to 6’9, so about 200,000 men. There are 130 NBA players in this band. So about one in every 1,500 people of this height is in the NBA.
0.003% of the US male population is 6’9 to 7’0, so about 5,000 men. There are 160 NBA players in this band. So about one in every 30 people of this height is in the NBA.”
The analysis breaks down at the extreme ends of the distribution where slight deviations from the normal distribution in height are more apparent. But, in the middle (where most of us are in terms of height) this analysis holds pretty well.
If you can imagine we lived in a world where people didn’t automatically know how tall they were, you might seriously consider taking a height test before devoting years of your life trying to make it into the NBA.
So if knowing how tall you are would be the obvious thing to do if you plan on entering a height-dominated field, why do we feel squicky about knowing our IQ given how many life goals we work on depend on it?
Arguments Against Knowing Your Own IQ
As Jay Cross mentioned earlier, a big worry people might have is that if they know their IQ is high, that will make them complacent so they won’t work very hard and reach their potential. If they know it is low, that will discourage them from trying, and so they won’t work hard and reach their potential.
We know that effort is an important factor in succeeding at anything, and we seem to put more effort in precisely when the outcome seems to depend on it. If our IQ is largely genetic and predicts the outcomes we’ll have in life, it may feel like the outcomes have been decided in advance. If they have, why bother trying?
The obvious counterargument for this is simple: even if IQ is predictive, it doesn’t perfectly predict outcomes. There’s still plenty of room for chance, effort and the million other things in life we can’t imagine to influence your outcomes. Even if you know your IQ, therefore, you’ll still want to try hard.
The argument against knowing your IQ therefore has to explain why we seem to have trouble keeping it in that perspective.
One way to think of it is that people have a tendency to over-explain their lives in terms of signals with weak or non-existent predictive power. Think of astrology. People throw themselves to believe that they are totally a Gemini or Libra because of the month they were born, and explain everything from their personality to the events of their life through that lens.
If it isn’t horoscopes, it’s the modern pseudoscientific equivalent: personality tests. While some tests [8] have scientific support, the incredibly popular Myers-Briggs test [9] is essentially a sciencey-sounding horoscope. Still, people love taking the tests and viewing their behavior as being totally INTJ, ENFP, HYZX or whatever.
Given that IQ tests actually do have predictive power, I think it’s a reasonable worry that people might fetishize it in the same way. Rather than treat it as a source of partial information that can adjust the mental percentages you weigh to particular outcomes, which seems to be difficult to do intellectually, people switch to explaining everything in terms of their IQ just as people currently do with bogus horoscopes or Jungian personality tests.
Another possible argument is that the issue isn’t with IQ, but our conception of it as being fixed. Studies show that IQ’s heritability increases with age [10]. One explanation for this is simply that environmental variables can push our IQ around a lot in early childhood, but eventually we settle onto our truer inherited value.
But another explanation is that IQ works through positive feedback. People who are a bit smarter when they’re younger (because of genetics) enjoy learning and cognitively demanding tasks more. By doing more of those tasks, they increase their IQ over time, widening the gap between them and those who didn’t like learning and cognitively difficult tasks.
In this second explanation, some of the perceived heritability of intelligence wouldn’t come just from having better mental hardware, but because enjoying the type of activities that increase intelligence is also heritable.
I’m not sure the split of evidence in favor of these two interpretations, or their relative prominence. But if the second one is a factor, then effort matters in your eventual intelligence. In this case, you might want to learn your IQ, assuming you adopt the perspective that it’s a partially trainable quality (like muscular strength) and not a mostly fixed on (like height).
A final argument against knowing could be that we already have good knowledge about our intellectual abilities and that IQ, far from adding more predictive power, actually distracts us because it is a cruder measurement than our own prior experiences (but has greater perceived legitimacy).
Most students know whether they’re good at school or not. So why not trust your dozens of years in an academic institution for guidance on whether you should go to college or what to major in, rather than a test that took only a few hours? Certainly that private experience not only includes details of your general cognitive ability but the many other factors that influence academic success (such as work ethic, habits, conscientiousness and interest).
From a rational, Bayesian perspective, more information can never hurt. However it may be that knowing a cruder instrument that has high perceived legitimacy, might cause you to exaggeratedly update your prior beliefs. Since we generally already have immense personal experience with cognitive tasks of different sorts, IQ would then appear to only offer information to the outside perspective where statisticians and psychologists can’t access our own intuitions and instead need to rely on hard numbers.
Still, all these arguments seem to weigh more in favor of taking IQ lightly, rather than ignoring it altogether.
Idiosyncratic Reasons for Ignorance
Ultimately I’m not sure. In presenting reasons for knowing or not knowing IQ, I feel like those on the side of knowing present a somewhat more convincing case. But I still can’t shake the gut aversion I have to taking an IQ test.
Maybe I have my own personal reasons for not wanting to take the test which would apply more to me than to others. After all, I’ve built a blog and following around learning accomplishments. If I took an IQ test and publicized it, what would that mean? If I have a higher-than-expected IQ, it might make it easy to dismiss the efforts I put in and the efforts other people put in who try to follow those projects. If I have a lower-than-expected IQ, it might undermine myself as a writer (who wants to listen to someone who isn’t very smart?).
My instinct, despite all the rational discussion I’ve presented is to ignore it and continue working on learning projects exactly as I have been before.
What do you think about knowing your IQ? Do you feel persuaded that it’s something worth knowing or ignoring? Share your thoughts in the comments.