With the full development of the genetic technologies described above …. , it might be possible to ensure that new individuals are on average smarter han any human who has yet existed
p43
This would be huge! Assuming IQ is normally distributed, there have been, there have been more than a billion people in history, so we could reasonably expect to have seen a 6-sigma IQ person—a person with an IQ of 190. So we’d need to see a 90point gain in average IQ.
Ok, now I see that Nick claims that 10 generations of 1 in 10 selection could give us that. So perhaps this should be a “part you find most surprising” rather than “part you find least persuasive”. I certainly would have spent a little bit more time on this possibility!
The normal distribution is just a model. You have to be very careful about expectations that happen at 6 sigma. Nothing guarantees your gaussian works well that far from the mean.
Yes, but leplen’s point is that the construction doesn’t map directly to reality. An ‘IQ score’ is not calculated by lining everyone up by raw score and determining where they fall; we create a mapping from raw scores to IQ from a reference distribution, and then compare people’s scores to the distribution.
As you might expect, the IQ tests start to lose statistical validity as you go further and further into the extremes. How well can we differentiate a person of 175 IQ and 190 IQ with our current tests? Not nearly as well as we can differentiate a person of 95 IQ and 110 IQ.
And the biological model of what makes people score particular ways on IQ tests looks normally distributed from afar, but is that true everywhere? Obviously not in certain cases (think of stuff like Down’s), and so possibly not so in the upper extreme, as well.
What did you find least persuasive in this week’s reading?
p43
This would be huge! Assuming IQ is normally distributed, there have been, there have been more than a billion people in history, so we could reasonably expect to have seen a 6-sigma IQ person—a person with an IQ of 190. So we’d need to see a 90point gain in average IQ.
Ok, now I see that Nick claims that 10 generations of 1 in 10 selection could give us that. So perhaps this should be a “part you find most surprising” rather than “part you find least persuasive”. I certainly would have spent a little bit more time on this possibility!
The normal distribution is just a model. You have to be very careful about expectations that happen at 6 sigma. Nothing guarantees your gaussian works well that far from the mean.
Isn’t IQ normally distributed by construction?
Yes, but leplen’s point is that the construction doesn’t map directly to reality. An ‘IQ score’ is not calculated by lining everyone up by raw score and determining where they fall; we create a mapping from raw scores to IQ from a reference distribution, and then compare people’s scores to the distribution.
As you might expect, the IQ tests start to lose statistical validity as you go further and further into the extremes. How well can we differentiate a person of 175 IQ and 190 IQ with our current tests? Not nearly as well as we can differentiate a person of 95 IQ and 110 IQ.
And the biological model of what makes people score particular ways on IQ tests looks normally distributed from afar, but is that true everywhere? Obviously not in certain cases (think of stuff like Down’s), and so possibly not so in the upper extreme, as well.
There are more than a billion people now! According to this article there have been around 108 billion people born ever.
Yes, but the mean IQ over those 108 is probably sub-100.