Why does IQ cluster around 100 points?

[rousseau]

I've been running through some ideas lately about why the IQ of most populations clusters around 100. It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

 

[J842P]

Um, isn't it normalized?

 

[rousseau]

Um, isn't it normalized?

You're answering the wrong question.

 

[J842P]

Um, isn't it normalized?

You're answering the wrong question.

Are you asking why IQ has a normal distribution?

Also, the idea that high IQ is maladaptive is certainly not new, and I think it is pretty reasonable and compelling.

The very high IQ people I know don't tend to be biologically fit.

Overall IQ, however, has been increasing dramatically. That is to say, someone who had an IQ of 100 in 1920 would probably score around an 80 now. This effect is way too fast to be explained by selection, likely, it is due to things like overall improved nutrition and a world that exercises the things that IQ measures more than the world of the average person from the 18th/19th century.

In any event, I would be careful of inferring too much from the shape of the distribution statically. A trait could be highly adaptive or maladaptive but the trait can still be normally distributed in a population at a given time. Especially a trait like IQ, which would be a classic example of continuous variation.

 

[rousseau]

Um, isn't it normalized?

You're answering the wrong question.

Are you asking why IQ has a normal distribution?

Also, the idea that high IQ is maladaptive is certainly not new, and I think it is pretty reasonable and compelling.

The very high IQ people I know don't tend to be biologically fit.

Overall IQ, however, has been increasing dramatically. That is to say, someone who had an IQ of 100 in 1920 would probably score around an 80 now. This effect is way too fast to be explained by selection, likely, it is due to things like overall improved nutrition and a world that exercises the things that IQ measures more than the world of the average person from the 18th/19th century.

In any event, I would be careful of inferring too much from the shape of the distribution statically. A trait could be highly adaptive or maladaptive but the trait can still be normally distributed in a population at a given time. Especially a trait like IQ, which would be a classic example of continuous variation.

The question isn't mathematical, the question is what reproductive advantage is there to people who fall within the average of the IQ distribution. Not is there an advantage, but what specifically is the advantage.

 

[Jokodo]

I've been running through some ideas lately about why the IQ of most populations clusters around 100.

Because that's how it's defined. IQ 100 isn't some objective value derived from natural constants, it is, per definition, the median.  Flynn effect: "When intelligence quotient (IQ) tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100 and their standard deviation is set to 15 or 16 IQ points. When IQ tests are revised, they are again standardized using a new sample of test-takers, usually born more recently than the first. Again, the average result is set to 100."

It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

The population does drift to the right - so fast in fact that it is highly doubtful that this is primarily, or even to a significant degree, a genetic effect. For the UK, the increase has been calculated as one standard deviation from 1942 to 2008.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

All of that may or may not be so, but IQs clustering around 100 points is the worst possible piece of evidence either way you could have come up with.

- - - Updated - - -

Are you asking why IQ has a normal distribution?

Also, the idea that high IQ is maladaptive is certainly not new, and I think it is pretty reasonable and compelling.

The very high IQ people I know don't tend to be biologically fit.

Overall IQ, however, has been increasing dramatically. That is to say, someone who had an IQ of 100 in 1920 would probably score around an 80 now. This effect is way too fast to be explained by selection, likely, it is due to things like overall improved nutrition and a world that exercises the things that IQ measures more than the world of the average person from the 18th/19th century.

In any event, I would be careful of inferring too much from the shape of the distribution statically. A trait could be highly adaptive or maladaptive but the trait can still be normally distributed in a population at a given time. Especially a trait like IQ, which would be a classic example of continuous variation.

The question isn't mathematical, the question is what reproductive advantage is there to people who fall within the average of the IQ distribution. Not is there an advantage, but what specifically is the advantage.

Assuming your conclusions?

 

[Politesse]

I've been running through some ideas lately about why the IQ of most populations clusters around 100. It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

The scale was designed that way...

 

[rousseau]

Assuming your conclusions?

Well for any trait that has a normal distribution, it would be pretty safe to say that there is reproductive value for people who hit the median. In the same way being an average height would be of value.

 

[ideologyhunter]

I'm pretty sure it was designed by the APA to appease the National Arts Council. Setting up the distribution encourages the phenomenon to occur in life. The distribution then affects the film industry, allowing for gigantic box office for Dwayne Johnson while allowing a livable market share for Jim Jarmusch. In literature, it allows for entire forests in the Pacific Northwest to become James Patterson titles, while allowing a decent share for Paul Theroux. Balance and diversity are the goals. (I forgot to mention that the polar opposites of Jarmusch and Theroux might be the Ernest movies and, in publishing, the works of Joyce Meyer.)

 

[Jokodo]

Assuming your conclusions?

Well for any trait that has a normal distribution, it would be pretty safe to say that there is reproductive value for people who hit the median. In the same way being an average height would be of value.

Can you make your reasoning here a wee bit more explicit?

 

[rousseau]

Assuming your conclusions?

Well for any trait that has a normal distribution, it would be pretty safe to say that there is reproductive value for people who hit the median. In the same way being an average height would be of value.

Can you make your reasoning here a wee bit more explicit?

If intelligence is heritable, which it is, and 68% of the population has an IQ between 85 and 115, and this proportion is relatively stable, this means that people in that range are producing children at a much greater rate than people with a significantly lower IQ or a significantly higher one. And if intelligence was completely arbitrary we wouldn't see a distribution at all, it would be random.

From that it follows that there is very little, to no discernible reproductive advantage of having an IQ above 115, as opposed to one between 85 and 115.

You could argue that the distribution is shifting right, and it possibly is, but theoretically there has to be an upper limit, intelligence can't increase infinitely.

 

[Jokodo]

Can you make your reasoning here a wee bit more explicit?

If intelligence is heritable, which it is, and 68% of the population has an IQ between 85 and 115,

68% of the population has an IQ between 85 and 115 as per the definition of "IQ 85/IQ 115". Whatever their intelligence by any other measure, this one follows from how "IQ" was set up to operate.

and this proportion is relatively stable,

Again, this follows from how IQs are defined. It couldn't be any other way whatever happens behind the curtains.

this means that people in that range are producing children at a much greater rate than people with a significantly lower IQ or a significantly higher one.

It doesn't mean any such thing because a) the way IQ is defined, b) the fact that a normal distribution is what you expect to get if intelligence (even if we were to measure it objectively) is the product of a multitude of unrelated factors, even if each of them has a uniform distribution, and c) a significantly higher (or for that matter lower) intelligence could well be selected for, as long as the additional benefit is small enough, you'd still expect a normal distribution.

And if intelligence was completely arbitrary we wouldn't see a distribution at all, it would be random.

Which adds up to a normal distribution as soon as there are multiple factors involved...

From that it follows that there is very little, to no discernible reproductive advantage of having an IQ above 115, as opposed to one between 85 and 115.

Nothing of that sort follows.

You could argue that the distribution is shifting right, and it possibly is, but theoretically there has to be an upper limit, intelligence can't increase infinitely.

You could say that, but that would be a totally different discussion from the one you started this thread with.

 

[Keith&Co.]

, the question is what reproductive advantage is there to people who fall within the average of the IQ distribution.

Near as i can tell, we don't see an evolutionary benefit from being smart because despite the Darwin Awards,being stupid is nowhere nearly lethal enough.

 

[rousseau]

Well, here is what Wikipedia has to say anyway.

 

[Bronzeage]

Why is a football field 100 yards long? Humans just like round numbers.

 

[untermensche]

The intelligence in humans that made them most fit to survive is group intelligence. The intelligence of a group working towards a goal, like the goal of killing some large predator or large powerful prey, or the goal of building shelter.

Individual intelligence is pretty meaningless and only has a chance to really express itself once civilization exists.

In small groups the most powerful might dominate, not necessarily the most intelligent.

 

[Speakpigeon]

The intelligence in humans that made them most fit to survive is group intelligence. The intelligence of a group working towards a goal, like the goal of killing some large predator or large powerful prey, or the goal of building shelter.

That's a very good point.

Individual intelligence is pretty meaningless and only has a chance to really express itself once civilization exists.

Still, I'm not sure there's anything other than specialised intelligence. Some people are good a Lego, others are good at relationships, etc. So, "group intelligence" wouldn't be enough of itself. You would need to have that plus the individual intelligence of at least some of the individuals in the group. A leader using the specialised skills of the others.

Still, this aspect seems a derail to me.
EB

 

[Speakpigeon]

I've been running through some ideas lately about why the IQ of most populations clusters around 100. It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

I think how intelligence interacts with fertility and the gene pool likely follows a very complicated law none of us is intelligent enough to break. I think we're stupid enough to make guesses, though.

My guess is that the intelligence of each individual, as it results and shows in behaviour, results from the interaction between a general capability and a focus of the mind of this individual on specific subjects of interest. The general capability would be essentially correlated to health, essentially the health of the brain. Health would be affected both by genetic factors and standards of living in rather unpredictable ways. Focus would be a matter of genes and life experience. Again, something very difficult to predict or even make proper observations about. Very intelligent people may only be interested in founding as large a family tribe as possible and thereby pass on their genes, experience and to some extent standards of living to many more descendants than me for example. But they may also be interested in things like logic and philosophy, possibly thereby missing out on their chance to reproduce and pass on their bright intellect. So, overall, too complicated a picture for us to sort out in any practical way. I think most intelligent people wouldn't spend any time on this issue. You'll see what happens to you anyway and I can assure you, trying to predict your own life is definitely a waste of time. Even idiots don't do it.
EB

EDIT
Hey, I think I'm the only one here to have replied with something more than a derail! Yes?

 

[Jokodo]

I've been running through some ideas lately about why the IQ of most populations clusters around 100. It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

I think how intelligence interacts with fertility and the gene pool likely follows a very complicated law none of us is intelligent enough to break. I think we're stupid enough to make guesses, though.

My guess is that the intelligence of each individual, as it results and shows in behaviour, results from the interaction between a general capability and a focus of the mind of this individual on specific subjects of interest. The general capability would be essentially correlated to health, essentially the health of the brain. Health would be affected both by genetic factors and standards of living in rather unpredictable ways. Focus would be a matter of genes and life experience. Again, something very difficult to predict or even make proper observations about. Very intelligent people may only be interested in founding as large a family tribe as possible and thereby pass on their genes, experience and to some extent standards of living to many more descendants than me for example. But they may also be interested in things like logic and philosophy, possibly thereby missing out on their chance to reproduce and pass on their bright intellect. So, overall, too complicated a picture for us to sort out in any practical way. I think most intelligent people wouldn't spend any time on this issue. You'll see what happens to you anyway and I can assure you, trying to predict your own life is definitely a waste of time. Even idiots don't do it.
EB

EDIT
Hey, I think I'm the only one here to have replied with something more than a derail! Yes?

The OP is a derail, replying with anything other than a derail is off topic.

 

[rousseau]

I've been running through some ideas lately about why the IQ of most populations clusters around 100. It seems strange to me that if intelligence, reason, and problem solving skill are generally considered positive traits, why the population doesn't drift to the right. Instead it seems like there is some kind of reproductive advantage of not being too smart.

But to take it a bit further I've been asking myself: well, what is a person like that's not too smart? Some thoughts:

- They're more likely to take social norms for granted
- They're less likely to question ideologies that act as social bonds
- They may be worse at family planning so reproduce more at the expense of their future
- High IQ might come at the expense of EQ, which is more critical to forming relationships

It's an interesting point to consider because it suggests that, in some ways, intelligence can be maladaptive. So it's possible that all of the issues we see with people and strange beliefs is a feature, not a bug, of our species.

Your thoughts?

I think how intelligence interacts with fertility and the gene pool likely follows a very complicated law none of us is intelligent enough to break. I think we're stupid enough to make guesses, though.

My guess is that the intelligence of each individual, as it results and shows in behaviour, results from the interaction between a general capability and a focus of the mind of this individual on specific subjects of interest. The general capability would be essentially correlated to health, essentially the health of the brain. Health would be affected both by genetic factors and standards of living in rather unpredictable ways. Focus would be a matter of genes and life experience. Again, something very difficult to predict or even make proper observations about. Very intelligent people may only be interested in founding as large a family tribe as possible and thereby pass on their genes, experience and to some extent standards of living to many more descendants than me for example. But they may also be interested in things like logic and philosophy, possibly thereby missing out on their chance to reproduce and pass on their bright intellect. So, overall, too complicated a picture for us to sort out in any practical way. I think most intelligent people wouldn't spend any time on this issue. You'll see what happens to you anyway and I can assure you, trying to predict your own life is definitely a waste of time. Even idiots don't do it.
EB

EDIT
Hey, I think I'm the only one here to have replied with something more than a derail! Yes?

Thanks for the reply, and yea that's the sense I was getting from the Wikipedia article. There is such an enormity of factors involved that it's almost impossible to isolate the answer. Kind of like in diet science.