Most intelligence researchers believe that intelligence can be reduced down to one single factor. They believe that there are not multiple types of intelligence, only multiple ways to measure the one type.
There are several reasons why I believe this is wrong, and that there are multiple types of intelligence.
Firstly, there are sex differences in spatial intelligence. Males are better than females in spatial tasks. This is well-established and has solid evolutionary reasons behind it. Refer to my post here for evidence.
However, females have a slight advantage in memory tasks.
These simple facts prove that memory and spatial ability are different types of intelligence. If they were not different types, but rather different ways of measuring the underlying g factor, then they would not produce consistent sex differences. This proves that intelligence cannot be reduced down to g.
Secondly, the man who discovered g also discovered that g diminishes as IQ increases. This is known as Spearman’s Law of Diminishing Returns (SLODR). What does this mean?
Let us understand that g is essentially just variance. If you have 10 different intelligence quizzes (eg. maths, vocabulary, mental rotation, memory etc.) and people score roughly the same on all of them, then there would be very little variance. You could then say that this shows a general intelligence, or g.
However, if people score very different on each test, then you the variance would be high, and you couldn't really say that there is a general intelligence.
In most cases, people do score the same, and variance is low, leading people to believe in g.
However, people with high IQ have greater variance across tests. So for some people, say with an IQ less than 130, there is a general factor of intelligence. Bu for others higher than 130, there might not be a general factor. How do we reconcile this and decide whether g really exists or not?
The best way I think is to realise that there are multiple types of intelligence, but they have limits. Think of them being tied to each other with rope. You can be better at memory than spatial ability, but the gap can never be too wide. Meaning there is some overlap between types if intelligence.
The gap can be wider as IQ increases. Why would this be?
It seems to me that the gap is wider as IQ increases, because the gap can afford to be higher. A smarter person can afford to be quite bad in some areas, because their overall intelligence will compensate for it.
An average person cannot afford to be bad in one area, they will have trouble finding ways around this problem.
Smarter people can afford to specialise.
In a social species, this can help greatly, where some group members will invent things, or be creative to solve some problem for the group.
References
Lynn, R. (2021). Sex Differences in Intelligence: The Developmental Theory. Arktos
Complete overlap would make other measures meaningless as they would be identical. The correlation between individual measurements attempts to get at an approximation of “g”, but there is error involved which makes the measurements imperfect, hence an (acknowledged) approximation of “g”. We have multiple measurements (subtests) in order to cancel out as much error as possible in our estimate (of “g”), but “g” does not entail/require complete overlap or perfect correlation. There may be some “aspects of intelligence” as you put it, but that is not related to the concept of “g” per se. The aspect/concept of different intelligences was indeed that which lead to “g” in the first place. All the attempts at measuring “different intelligences” always wound up with collections of correlated sub-test scores.
I myself have no problem with “g” *and* different intellectual strengths and weaknesses as indicated by subtests. To me, “g” is like a measure of a highly efficient brain. The higher the “g”, the more “horsepower” so to speak. Whether the car powered by this engine has superior ability in handling curves, or off-road traction, or acceleration is not a show stopper for me.
Somehow author hasn't understood how group factors work before deciding to blog on it. A sex difference on a given test depends on its loading on g and the group factors, as well as the sex differences on each group factor. Men have a big advantage on the spatial factor and women a smaller advantage on the short term memory factor. The big debate is about the g factor difference, which Lynn, me etc think is about 4 IQ.