An IQ score is not a measure of how much intelligence you have. It is a statement about where your performance on a particular set of reasoning tasks sits relative to other people who took the same tasks. That distinction sounds pedantic until you see how often it is ignored — in marketing, in arguments, and in the way people talk about their own results.
The scale is built, not discovered
Modern scores use a deviation scale: the average is fixed at 100 and the standard deviation at 15. Those numbers are conventions. They were chosen so that scores spread out in a familiar, readable way, and so that roughly two thirds of people land between 85 and 115. Nothing in the brain corresponds to the number 100; it is the midpoint of a ruler somebody designed.
A useful comparison is shoe sizing. A size 10 is a real, repeatable fact about your foot, but the number 10 is arbitrary — it is 44 in Europe and 9.5 in the UK for the same foot. Nobody concludes their feet grew on a flight to Paris. IQ numbers work the same way: the underlying performance is real, the number attached to it depends entirely on the scale and the group it was set against.
This is why comparing scores across different tests and different eras is treacherous. A score only means something in relation to the reference group it was scaled against. Change the group and the same performance produces a different number.
Percentiles say more than the score does
If your score is 115, the useful statement is not "115" but "around the 84th percentile" — roughly 84 out of 100 people in the reference sample scored lower. Percentiles also make the compression at the extremes visible. The gap between 100 and 110 covers a lot of people; the gap between 140 and 150 covers very few. Ten points is not always ten points.
Think about running times instead of scores for a moment. Going from a 30-minute 5k to a 27-minute 5k moves you past a huge crowd of recreational runners. Going from 15 minutes to 14 minutes is a far smaller clock change and a far bigger achievement, because almost nobody is in that stretch of the distribution. Test scores compress in exactly the same way at the top and bottom, which is why two people arguing over a five-point difference are usually arguing about noise.
Every score carries error
Testing is measurement, and measurement has error. Your attention, your sleep, your familiarity with the question formats and plain luck on a handful of items all move the number. Supervised clinical tests reduce that error; they do not eliminate it, which is why psychologists report confidence intervals rather than bare figures. Brain Rate reports a range for the same reason. A range of 108-122 is not vagueness — it is the honest version of a claim that a single number would overstate.
You already accept this elsewhere without complaint. A bathroom scale that reads 74.3kg in the morning and 75.1kg at night has not measured two different bodies, and an election poll reported as 47% with a three-point margin is understood by everyone to mean "somewhere in the mid-forties". A single, decimal-free IQ number is the equivalent of a poll headline that drops the margin of error — tidier to read, and misleading for exactly that reason.
What a score is not for
- It is not a prediction of your career, income or worth.
- It is not fixed for life, and it is not a personality description.
- It is not a diagnosis. Learning differences and attention conditions need a clinician, not a test result.
- It is not evidence for any consequential decision — hiring, placement, legal or medical.
The everyday failure mode is small and quiet rather than dramatic. Someone scores in the low nineties on a phone at midnight, decides they are "not a numbers person", and steers away from the accounting module or the data role they were curious about. Nothing in a reasoning score licenses that decision. It describes an hour of performance on abstract puzzles, not the ceiling of what you can learn when you spend a year on something.
What it is good for is narrower and more interesting: a rough, honest read on how you handle certain kinds of abstract reasoning, and a profile showing where you are comparatively stronger and weaker. Read at that level, it is genuinely informative. Read as a verdict on a person, it is nonsense.