What is the IQ scale based off of?
What difference does 1 IQ more make? or 10 more make?
Can it ever change over time or is it a creature’s/person’s own level of understanding rather than what they know?
In: Biology
It can change over time, and most versions of how it is tested/used are meant to measure a child’s development *compared to other people their age*. A kid with a high IQ does not (necessarily) have more knowledge or skills than an adult with a lower IQ, because the adult has years of learning and development more than the child has. It also doesn’t mean that child will continue to learn and develop well unless they have the education etc available that’s needed for that.
As a comparative scale, the numbers are based on standard deviations, so they tell you where people fall on a bell curve, which has a lot of people who fall near the middle with it becoming increasingly rare to be far away from there. 10 points is 1 standard deviation. 100 is the average score and about 2/3 of people fall within 10 points (one deviation) either up or down from there. But in that area there is a *ton* of variation, it is not at *all* unusual for somebody to have a score closer to 110 compared to the “true” average of 100. But variation, and the number of people in each group, decreases as you get to higher scores. For somebody to have an IQ of 130 or higher has a rarity of almost 1 in 1000. A few more points could make them 1 in 2000.
This doesn’t mean they’re “twice as smart” but it puts them slightly higher in a group of people that is already exceptional, therefore it is very rare for people to have an IQ that high.
The scale is basically a [normal distribution](https://en.m.wikipedia.org/wiki/Normal_distribution) centered around an average of 100. Every 15 points is one standard deviation. 85-115 holds about 70% of the population. 70-130 covers 95%, and 99.7% of the population falls between 55 and 145. At least, that’s how it was intended. The average test score has shifted over time (generally but not always up). Usually when a new test is created, the scores are standardized as above, but the same people taking older tests will average out to greater than 100.
The IQ scale is set by what your mental age is, vs your actual age, times 100. So, if you’re 25, and you are as mentally able to function as a 25 year old should be, your IQ would be 100, which is the average.
IQs do change over time. Population IQs rise by three points every ten years. 10 points is just the standard deviation. (Think using the same ruler to measure in either direction from the middle.) A lot of people are over-proud about their IQ scores, but I find it humbling to think that a 50 IQ is just as different from the average as a 150 IQ is. They aren’t 1/3rd as smart as the other… they have something very much in common.
Side fact: since a person below a certain IQ level cannot be given a death sentence for a crime, there have been cases where lives have been protected by adjusting for IQ inflation.
It’s important to realize that IQ is not a precise measurement. Measuring intelligence is extremely difficult as there are many different ways in which we learn and apply skills, and even on a day to day basis we function at differing levels.
IQ was simply an attempt to try and measure intelligence in a person, but it cannot tell the whole picture, just a very vague idea that someone may have higher or lower aptitude for learning. 100 being statistically the average.
It’s similar to being able to tell how good someone is at a skill like playing darts. The score in a single game may not represent their skill, but if a person consistently can score high, you get the idea that they’re pretty good at the game. That said, just like with game scores, IQ of a few points here and there doesn’t tell you that much.
IQ is calculated by comparing a score determined from how well you did on a specific test compared to the expected result given your age, so yes it will change over time. An IQ of 100 means you did exactly as expected. If you get older but don’t improve on the test, your IQ will decline. It should be noted that IQ was created to measure a child’s mental development, and children are expected to improve mentally as they get older. Once you’re an adult, of course, that isn’t the case. IQ doesn’t measure knowledge, it measures a person’s ability to think critically and reason in certain ways.
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