Why does IQ cluster around 100 points?

[Jokodo]

Plausible and implausible can be operationally defined. Please try that since this is a science forum. Then maybe someone can make sense of things.

That sounds like a reversal of the burden of proof. It's rousseau postulating a hypothesis, it's his job to show it's plausible. The default is implausible, especially when it relies on mechanisms we know not to have been in place before 60-100 years ago having shaped human nature for millennia: Up to 60 years ago, how many kids you had depended more on how much sex you had than on how many you wanted (of course, that's hyperbole, but only slightly); up to 100 years ago, your reproductive success depended more on the survival rate of your kids than on their number.

Oh and I think one can make a strong argument that more than 50% of all humans who have ever lived are not hunter gatherers.

https://www.scientificamerican.com/article/fact-or-fiction-living-outnumber-dead/

All one needs to do is check rates since about 10k years ago when the ratio of farmer or sedentary to migrant or hunter gatherer changed dramatically in favor of those who did not routinely move of hunt. This also corresponds to populations exceeding 250,000 at any one time. Another simplification would be to presume generations are 20 years to reduce the need for continuous change versus longevity given longevity began it's latest increase around the time farming was established. Also presume longevity rose above 50 in 1900.

So although humans minimally have been around for 50k years their populations have only been over 250k for about 10k years. For convenience one can presume 100% before 10k were HG and 100% after 10K were sedentary. Evben if one adjusts for continuous decline in HG to today's about 2% I'm sure that with the as a starting point one can see more later than sooner even though only about 7% of all humans are alive now. I leave calculation to those who really need to do such things.

That may be so, but it doesn't affect my argument. If you carefully read my post, you will indeed find that it's peasant populations I used to illustrate that things were different in the past.

My argument survives as long as 0% of people older than our great-grandparents lived in post-industrial societies with ready access to modern contraception.

 

[rousseau]

That sounds like a reversal of the burden of proof. It's rousseau postulating a hypothesis, it's his job to show it's plausible.

Honestly, I don't think the evidence exists to solidly support any type of theory. I could try to track data down, but even if I did it would still be a stretch. So we're basically left with conjecture, which is what I'm doing.

I think the evidence that does exist is pretty clear that after a point intelligence and fertility are negatively correlated, though, and that fertility rates of people within a certain window are higher than those outside of the window:

https://www.sciencedirect.com/science/article/pii/S0160289607000244

Many studies have found a small to moderate negative correlation between IQ and fertility rates. However, these studies have been limited to the United States and some European countries. The present study was a between-nation study using national IQ scores and national fertility rates. There were strong negative correlations found between national IQ and three national indicators of fertility.

From there I don't think it's a huge stretch to consider that the evolutionary make-up of the average human mind is oriented in such a way to ensure the likelihood that babies are made, intelligence being a component of such minds. Given the negative correlation between IQ and fertility, it's likely that less intelligence leads to a greater propensity for having kids.

Why? I'd guess because within the sweet-spot culture is normalized and an alternative isn't really known. If financial security is there, babies happen. Yes, it's conjecture, but I don't think it's a huge stretch.

I'm not trying to convince anyone, though, I'm just looking for an answer to the problem and so far this is the only one that makes any sense to me.

 

[bilby]

That sounds like a reversal of the burden of proof. It's rousseau postulating a hypothesis, it's his job to show it's plausible.

Honestly, I don't think the evidence exists to solidly support any type of theory. I could try to track data down, but even if I did it would still be a stretch. So we're basically left with conjecture, which is what I'm doing.

I think the evidence that does exist is pretty clear that after a point intelligence and fertility are negatively correlated, though, and that fertility rates of people within a certain window are higher than those outside of the window:

https://www.sciencedirect.com/science/article/pii/S0160289607000244

Many studies have found a small to moderate negative correlation between IQ and fertility rates. However, these studies have been limited to the United States and some European countries. The present study was a between-nation study using national IQ scores and national fertility rates. There were strong negative correlations found between national IQ and three national indicators of fertility.

From there I don't think it's a huge stretch to consider that the evolutionary make-up of the average human mind is oriented in such a way to ensure the likelihood that babies are made, intelligence being a component of such minds. Given the negative correlation between IQ and fertility, it's likely that less intelligence leads to a greater propensity for having kids.

Why? I'd guess because within the sweet-spot culture is normalized and an alternative isn't really known. If financial security is there, babies happen. Yes, it's conjecture, but I don't think it's a huge stretch.

I'm not trying to convince anyone, though, I'm just looking for an answer to the problem and so far this is the only one that makes any sense to me.

Your conjecture is contradicted by the fact that throughout history, number of children born is negatively correlated with financial security - and that this trend has accelerated as people become wealthier overall.

Financial security is not only NOT a prerequisite for having children; It has consistently been observed to have the effect of reducing the number of children people have.

 

[rousseau]

Honestly, I don't think the evidence exists to solidly support any type of theory. I could try to track data down, but even if I did it would still be a stretch. So we're basically left with conjecture, which is what I'm doing.

I think the evidence that does exist is pretty clear that after a point intelligence and fertility are negatively correlated, though, and that fertility rates of people within a certain window are higher than those outside of the window:

https://www.sciencedirect.com/science/article/pii/S0160289607000244



From there I don't think it's a huge stretch to consider that the evolutionary make-up of the average human mind is oriented in such a way to ensure the likelihood that babies are made, intelligence being a component of such minds. Given the negative correlation between IQ and fertility, it's likely that less intelligence leads to a greater propensity for having kids.

Why? I'd guess because within the sweet-spot culture is normalized and an alternative isn't really known. If financial security is there, babies happen. Yes, it's conjecture, but I don't think it's a huge stretch.

I'm not trying to convince anyone, though, I'm just looking for an answer to the problem and so far this is the only one that makes any sense to me.

Your conjecture is contradicted by the fact that throughout history, number of children born is negatively correlated with financial security - and that this trend has accelerated as people become wealthier overall.

Financial security is not only NOT a prerequisite for having children; It has consistently been observed to have the effect of reducing the number of children people have.

This would take a while to unpack completely, but I'll try to be brief:

First - define financial security. It doesn't necessarily mean wealthy, just ability to raise ones kids to adulthood by any given means. This could mean modest agriculture, could mean welfare state, does not imply wealth. All it implies is that food is present so kids don't die. By this definition the poorest of the poor in Africa have some means of financial security.

Second - even if some means of financial (let's call it food).. food security isn't present, this re-iterates the theme that those of less intelligence will have more kids despite that being problematic. So the trend will exist on the lower end of the spectrum, rather than the higher. This reinforces the theme that those of lower IQ are worse at avoiding having children.

Third - where real wealth is negatively correlated to fertility this is a result of children being expensive to raise. This doesn't indicate less of a propensity to have kids, but rather less capacity to have kids. Different issues, but still those with less intelligence will be more likely to overreach their capacity.

So I don't think your argument quite hits its target in reference to my post.

 

[Under the Rose]

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 come late to this discussion and have not the time to read all of the responses though I have reviewed a cross section of them.

My person thoughts on the matter from observations in my own life and country would be that we are a 'herd species' like several others and the larger group determines the parameters of 'acceptance'. Those who are too different from the average get selected against in many ways, some obvious and others more subtle. Historically, our education system was geared toward the average and extremely intelligent students were just as likely to opt out as those who were lacking.

Being too different led to bullying and disenfranchisement while if born into wealth or power, such individuals were merely regarded as eccentric.

Follow the money. Currently our society is making a strong verbal show of supporting 'individualism' on many fronts but the actual cash flow does not reflect those values. They are merely convenient politics. Our god is still the GDP numbers and my thoughts are that where the average IQ is presently pegged has proven to be the most profitable for industry to this time though I strongly suspect that is about to change.

 

[Trausti]

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 come late to this discussion and have not the time to read all of the responses though I have reviewed a cross section of them.

My person thoughts on the matter from observations in my own life and country would be that we are a 'herd species' like several others and the larger group determines the parameters of 'acceptance'. Those who are too different from the average get selected against in many ways, some obvious and others more subtle. Historically, our education system was geared toward the average and extremely intelligent students were just as likely to opt out as those who were lacking.

Being too different led to bullying and disenfranchisement while if born into wealth or power, such individuals were merely regarded as eccentric.

Follow the money. Currently our society is making a strong verbal show of supporting 'individualism' on many fronts but the actual cash flow does not reflect those values. They are merely convenient politics. Our god is still the GDP numbers and my thoughts are that where the average IQ is presently pegged has proven to be the most profitable for industry to this time though I strongly suspect that is about to change.

Humans are not herd animals. We are predators with hierarchy. Being different/individual isn't bad if it gives you a selective edge.

 

[untermensche]

Humans were a lot more scavenger than predator in their history. They cannot chase down their prey. They hunt in a coordinated group with each member acting autonomously, not by using a hierarchy. Just like a pack of dogs.

The only hierarchy that is natural to humans is the hierarchy of the bully. We have moved beyond that. The natural hierarchy has no legitimacy anymore.

But a modern human is nothing like the first humans, even if they are the same exact thing genetically.

A modern human does not hunt or kill. It is a weak frail thing totally dependent on having a society for survival and prosperity. And most are forced to submit to unnatural illegitimate hierarchies because they have no choice.

 

[George S]

Humanity arose in Africa. Their environment was such that they didn't have to be exceptionally brilliant because resources were essentially free. Their competition was not other species but other tribes. When we left Africa for colder climes the need to plan ahead arose; winter had to be planned for. As a result the emigrant population had to get smarter then those who stayed in Africa.

In those tribes those whose male population varied widely from dumb brute to brilliant leader while the female population clustered around the average succeeded. A randomly chosen woman is likely to be closer to 100 IQ than a randomly chosen man. Tribes that had three populations survived better: the fighting males, the leadership males and not stupid but not brilliant women. Stupid women did not reproduce or did not raise their children well. Brilliant women were not content to stay at home and raise children.

The Australian aborigines average around 65, the sub-Saharan Africans around 70, the northern Africans and Arabs around 85, the Maori about 90, the southern Europeans around 95, the northern Europeans (the standard) 100, and east Asian around 105. One group, the Ashkenazim, had a severe culling during the Russian pogroms and only the smartest survived leading to a 115 average.

The world population has, on average, around 90 and with today's blending of races that may become the most common IQ everywhere over time.

Criminality, regardless of race, peaks around 84 so it is predictable that an area populated by mostly 85 IQ people will be high crime areas. The unproven theory is that below 80 they're so dumb they get caught and those 90 and above don't need to be criminal to succeed.

There are high and low IQ people among all the races. Although the IQ of groups can be used to predict behavior of the group, it is not appropriate to judge any given individual by their group's average IQ.

 

[bilby]

Humanity arose in Africa. Their environment was such that they didn't have to be exceptionally brilliant because resources were essentially free. Their competition was not other species but other tribes. When we left Africa for colder climes the need to plan ahead arose; winter had to be planned for. As a result the emigrant population had to get smarter then those who stayed in Africa.

In those tribes those whose male population varied widely from dumb brute to brilliant leader while the female population clustered around the average succeeded. A randomly chosen woman is likely to be closer to 100 IQ than a randomly chosen man. Tribes that had three populations survived better: the fighting males, the leadership males and not stupid but not brilliant women. Stupid women did not reproduce or did not raise their children well. Brilliant women were not content to stay at home and raise children.

The Australian aborigines average around 65, the sub-Saharan Africans around 70, the northern Africans and Arabs around 85, the Maori about 90, the southern Europeans around 95, the northern Europeans (the standard) 100, and east Asian around 105. One group, the Ashkenazim, had a severe culling during the Russian pogroms and only the smartest survived leading to a 115 average.

The world population has, on average, around 90 and with today's blending of races that may become the most common IQ everywhere over time.

Criminality, regardless of race, peaks around 84 so it is predictable that an area populated by mostly 85 IQ people will be high crime areas. The unproven theory is that below 80 they're so dumb they get caught and those 90 and above don't need to be criminal to succeed.

There are high and low IQ people among all the races. Although the IQ of groups can be used to predict behavior of the group, it is not appropriate to judge any given individual by their group's average IQ.

Cool story, bro.

It's almost a shame to point out that these kinds of just-so stories are valueless; That this specific story is deeply mistaken in almost every possible way (according to actual archaeological and anthropological research, and to the actual definition of IQ); and that it is a narrative that was discredited over a century ago - which however didn't prevent it from being used as a foundation for racist atrocities ever since.

Hey, at least the first sentence is probably right.

 

[untermensche]

Humanity arose in Africa. Their environment was such that they didn't have to be exceptionally brilliant because resources were essentially free. Their competition was not other species but other tribes....

Utter nonsense. Human populations in Africa dwindled greatly. It was extremely difficult to survive.

Ever heard of these things called lions and hyenas?

What resources were free? What are you talking about?

 

[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 come late to this discussion and have not the time to read all of the responses though I have reviewed a cross section of them.

My person thoughts on the matter from observations in my own life and country would be that we are a 'herd species' like several others and the larger group determines the parameters of 'acceptance'. Those who are too different from the average get selected against in many ways, some obvious and others more subtle. Historically, our education system was geared toward the average and extremely intelligent students were just as likely to opt out as those who were lacking.

Being too different led to bullying and disenfranchisement while if born into wealth or power, such individuals were merely regarded as eccentric.

Follow the money. Currently our society is making a strong verbal show of supporting 'individualism' on many fronts but the actual cash flow does not reflect those values. They are merely convenient politics. Our god is still the GDP numbers and my thoughts are that where the average IQ is presently pegged has proven to be the most profitable for industry to this time though I strongly suspect that is about to change.

Humans are not herd animals. We are predators with hierarchy. Being different/individual isn't bad if it gives you a selective edge.

I agree with this, although toward the lower end of the spectrum of intelligence you may get something like this happening. Those intellectually incapable of finding and building a sustainable relationship, for instance, will be selected against. It's just not necessarily the same issue on the opposite side of the spectrum, although it would seem it can be with various types of neuroses.

 

[Elixir]

Humans are not herd animals. We are predators with hierarchy. Being different/individual isn't bad if it gives you a selective edge.

I agree with this, although toward the lower end of the spectrum of intelligence you may get something like this happening. Those intellectually incapable of finding and building a sustainable relationship, for instance, will be selected against. It's just not necessarily the same issue on the opposite side of the spectrum, although it would seem it can be with various types of neuroses.

Humans are opportunistic omnivores, not exclusively predators.
Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250? I don't think any tests have been devised to catalog that. IOW, isn't it possible that the height of the bell curve is a remnant of the measurement process?
Late to the game here and it's a long thread so, sorry if this has been discussed.

 

[bilby]

Humans are not herd animals. We are predators with hierarchy. Being different/individual isn't bad if it gives you a selective edge.

I agree with this, although toward the lower end of the spectrum of intelligence you may get something like this happening. Those intellectually incapable of finding and building a sustainable relationship, for instance, will be selected against. It's just not necessarily the same issue on the opposite side of the spectrum, although it would seem it can be with various types of neuroses.

In a tribal/small village environment, being intellectually incapable of finding and building a sustainable relationship is not selected against, as long as those who have those traits have sex at least occasionally. A child whose parents don't care for it will be raised by the village. Indeed, so will a child whose parents DO care for it.

 

[bigfield]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

 

[bilby]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

I am not sure that scores below zero are impossible (at least in principle, if not in practice given the way tests are written).

If IQ had been defined to produce an average of zero - that is, if the definition of IQ were identical to the current definition, but with 100 subtracted from every score - what would then be the lowest possible score, and why? It seems intuitively obvious that zero is a barrier none shall fall below, (ie that it is what you score if you get every question wrong, no matter how simple the question) but I am unsure that this is or should be necessarily the case. If IQs are normally distributed, then there shouldn't be an upper or a lower limit to the distribution, for an arbitrarily large population.

Or am I missing something?

 

[bigfield]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

I am not sure that scores below zero are impossible (at least in principle, if not in practice given the way tests are written).

If IQ had been defined to produce an average of zero - that is, if the definition of IQ were identical to the current definition, but with 100 subtracted from every score - what would then be the lowest possible score, and why? It seems intuitively obvious that zero is a barrier none shall fall below, (ie that it is what you score if you get every question wrong, no matter how simple the question) but I am unsure that this is or should be necessarily the case. If IQs are normally distributed, then there shouldn't be an upper or a lower limit to the distribution, for an arbitrarily large population.

Or am I missing something?

I see your point about limits. But the "quotient" in intelligence quotient is (edit: historically) the ratio of a person's "mental age" and their actual age. If the test evaluates a person's mental age to be negative, then that should be a clue that the test isn't measuring what we think it is.

 

[Elixir]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

? That would make sense. But even as a 10 year old I remember conjectures about dead guys' IQs that ranged above 200. They had Goethe at 210. And googlespeak has this even this day. I assume that "recorded" means they actually tested, which I would doubt about Goethe:

The highest IQ score ever recorded

Ainan Celeste Cawley (IQ score: 263)
William James Sidis (IQ score: 250-300)
Terence Tao (IQ score: 225-230)
Marilyn Vos Savant (IQ score: 228)
Christopher Hirata (IQ score: 225)
Kim Ung-Yong (IQ score: 210)
Edith Stern (IQ score: 200+)
Christopher Michael Langan (IQ score: 190 – 210)

 

[Elixir]

I see your point about limits. But the "quotient" in intelligence quotient is (edit: historically) the ratio of a person's "mental age" and their actual age. If the test evaluates a person's mental age to be negative, then that should be a clue that the test isn't measuring what we think it is.

But if a 2 week old baby is writing mathematical conjectures and critiquing Shakespeare, would that algorithm apply? He'd have an IQ of about a zillion. Still not quite the opposite of the zero IQ of the comatose baby, though. The good news for the comatose baby is that his IQ can't go down. Whereas the rest of us... can console ourselves that our inevitably nosediving IQs are recompensed by decades' accumulation of hard-won wisdom.

As the victim of too many IQ tests as a child, some lasting 3-4 hours, I can tell you two things:

1) The tests measure a limited frequency range within the real spectrum of "intelligence", almost no matter how you define or understand intelligence.
2) My IQ has gone down since I was as a kid. Even if I was still kid age, it will have gone down. Not only because of my age-related decline, nut also because those tests are comprised of bunches of little skillsets that greatly improve with practice. And if they're testing you all the time, practice is unavoidable. I got good at taking those tests. But few of those skillsets apply to anything but taking IQ tests so I will have long forgotten most of it.

 

[Elixir]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

I am not sure that scores below zero are impossible (at least in principle, if not in practice given the way tests are written).

If IQ had been defined to produce an average of zero - that is, if the definition of IQ were identical to the current definition, but with 100 subtracted from every score - what would then be the lowest possible score, and why? It seems intuitively obvious that zero is a barrier none shall fall below, (ie that it is what you score if you get every question wrong, no matter how simple the question) but I am unsure that this is or should be necessarily the case. If IQs are normally distributed, then there shouldn't be an upper or a lower limit to the distribution, for an arbitrarily large population.

Or am I missing something?

No, that's right I think. The problem lies in the inability to test for very low or very high IQ's, then. That's probably why the mean isn't zero - it messes with that pretty bell curve, and raises the likelihood that if those extremes were measured, there might be a long thin tail off to the right, and would end abruptly on the left.

 

[Loren Pechtel]

Clustering of IQ measurements probably has a lot to do with inability to accurately evaluate the extremes. On the left of the curve, zero is not attainable short of death or a congenitally comatose individual. At the other end, are there even ways to measure an IQ in excess of say, 250

IQ is supposed to be normally distributed with a mean IQ of 100. Since scores less than zero are impossible, scores greater than 200 should also be impossible. Based on that, scores over 200 should indicate that the testing instrument isn't giving accurate scores.

IQ is not normally distributed. It's close enough that we consider it normal but obviously the tail on the low side must be chopped.