For decades, academia has been debating the viability of the Intelligence Quotient (IQ). The debate seems to revolve around whether or not IQ tests can offer meaningful information about intellect. Why does it matter?
The psychiatric community and academia have been using IQ tests as a way to quantify the ability of people to process information. The results are often used to categorize people into "intellectual groups." It's also used to identify individuals who might have some kind of learning or information-processing disability. Mostly, test scores are used as a means of comparing people within a given group.
Before moving forward, it's important to note there are dozens of different IQ tests available. Each type goes about testing for intelligence in a different way. With that said, they all come back to a common scale that is often used as the means for categorizing people within any given group.
One of the most popular IQ comparisons is the comparison that takes place within an age group. This type of age comparison is also used to compare one age group with another. It's this latter comparison that will be the focus of this writing.
Why is an IQ Comparison By Age Relevant?
Presumably, we all get smarter with age. Our intellect is intended to increase as we get more education and more life experiences. Caution: IQ tests don't really test for details of what people have learned in school or in everyday life. Instead, these tests are specifically designed to test how people process information.
As everyone gets older, they should know more in terms of details and facts. Hopefully, they have also learned how to think more complexly and be able to solve more difficult problems with constructive or logical thinking. This is the true secret of education. Educators aren't supposed to be teaching facts, they are supposed to be teaching students HOW TO THINK. Quite literally, IQ tests test for a test taker's ability to think.
Age comparisons are typically done to measure an individual's intellectual progression. If a 12-year-old were to take the same IQ test as a college student, everyone would assume that the college student would score higher. Why? The college student has had more time to develop their intellect.
If the results of a comparison between a 12-year-old and a college student were other than expected, there would be one of two viable explanations. Either the 12-year-old is gifted or the college student has some type of learning disability.
This conflict gets resolved by comparing the 12-year-old with other 12-year-olds and or the college student with other college students. If the 12-year-old's test results fell within their age group, the college student might have a learning disability that needs to be addressed. Likewise, a college student that tested within the range of other college students would likely indicate that the 12-year-old is gifted.
To measure an individual's progression, it makes sense that they would need to take the same IQ test as they go through each relevant age group. In this case, the expectation is that the individual's intellect would increase at each level and presumably fall within the average for each age group. That would represent a natural progression of intellect.
The Scales BY Age
Now that you have a better understanding of why average IQ matters, it's time to look at the details. Remember that while different IQ tests will differ in terms of the process, they all report back to a common scale.
The IQ scale assumes a standard average score of 100 with a standard deviation of 15. For comparative purposes, each rate of distribution and category is assigned a "label" which is generally used to define each person's intellect. Here is the typical IQ scale and associated label:
140 or higher - .13% - Genius
120 to 139 - 2.14% - gifted or highly intelligent
110 to 119 - 13.59% - above average
90 to 109 - 34.13% - higher average
80 to 89 - 13.59% - lower average
70 to 79 - 2.14% - borderline deficiency” or borderline low
Below 60 - .13% - low IQ
Now, let's take a look at the average IQ by age to determine the progression of intellect. We'll start with a chart for children from 1 year old to 16 years old. We'll then provide a chart from 17 years old to senior age.
Chart for children:
1-year-Old - between 1 and 10
2-year-Old - between 1 and 10
3-year-Old - between 1 and 10
4-year-Old - between 5 and 20
5-year-Old - between 5 and 20
6-year-Old - between 5 and 20
7-year-Old - between 10 and 30
8-year-Old - between 10 and 30
9-year-Old - between 10 and 30
10-year-Old - between 30 and 50
11-year-Old - between 30 and 50
12-year-Old - between 40 and 65
13-year-Old - between 40 and 65
14-year-Old - between 60 and 80
15-year-Old - between 70 and 90
16-year-Old - between 70 and 90
Chart for adults
16 to 17 - 108
18 to 19 - 105
20 to 24 - 99
25 to 34 - 97
35 to 44 - 101
45 to 54 - 106
55 to 64 - 109
65 to 69 - 114
70 to 74 - 119
Note: After 74 years old, the average IQ starts to drop dramatically. It's at this age that health issues like dementia start to influence numbers.
Explanations
Since you probably expected continual progression upwards, a couple of things from these charts warrant explanation.
Average IQ increases until age 18 and then starts dropping slightly. Why? This is the age at which more than half the population ceases the formal education process. Over the next 16 years, the average continues to drop further as people get further from the educational process.
It's noteworthy that the average IQ starts rising again at about age 35. Why is that? It's at that age that life experience and maturity start factoring into the development of intellect. The simple fact is people reach a point where they can't help but be better thinks simply because they have so many experiences in life, experiences that challenge them to think and reason.
The average person's intelligence continues to grow into their mid-70s as life experiences accumulate. It's only at age 75 that a lot of people start to experience some level of diminished mental capacity.
In conclusion, you should take your IQ score too seriously. It's simply an indication of your intellect at any given point in your life. Learn more on how to take an IQ test here.