short takeaway: it’s really not all it’s cracked up to be
1 — IQ or Intelligent Quotient has no useful definition
The usual definition, one used by textbooks, is that an IQ is what the IQ test measures. Not the greatest definition but I have never seen a better one.
Here, for example, is a 2020 definition from Wikipedia:
An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence.
There are many kinds of intelligence and many kinds of cognitive tests. Each test measures only some of these intelligences — and only at one given point in time. People grow, people develop, people change….so do test scores.
Yes, I do know there is some correlation between some tests over some periods of time, but I also know there are many other factors to weigh in.
2 — When reporting IQ scores, the standard deviation is universally ignored
Standard deviation is the variance around a mean or average. Every measurement has a standard deviation, not just IQ measurements.
Most human measurements fall into what is called a bell curve or a normal curve — like the one in the image above.
In that curve, 100 is always the average IQ score. Each black mark on the line is one standard deviation. I added the scores that would go with each standard deviation.
For every IQ score, the set standard deviation is 15 — so your IQ is your test score +/- 15 — but we almost never read that.
For example, if your score on an IQ test came out to be 120 — your actual IQ could range from 105 to 135.
Yes — it could be anywhere within that 30 points! With the labels we use for the test numbers, you could…
