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Reaction times are strongly correlated with IQ which, in turn, has strong inverse correlations with many of the characteristics for people who are, and have bee

Reaction times are strongly correlated with IQ which, in turn, has strong inverse correlations with many of the characteristics for people who are, and have been, reproducing the most. The paper proposes this, 'dysgenic fertility', as a possible explanation. As an aside this is not an implicit reference to e.g. Africa. This problem exists on an international and intranational level. E.g. in the US people who have household income of less than $10,000 have a fertility rate 150% that of those with a household income greater than $200,000 with a surprisingly smooth fertility:income gradient between the two. [1] Crucially, the heritability of IQ seems to be only increasing the more we learn about it. Older studies showed it to 'only' be around 60% with more modern research indicating it is upwards of 80%. [2] One peculiar, and confounding effect, here is how IQ behaves on youth. In young age environmental conditions can play a more substantial role in IQ, yet as youth approach adolescence and beyond their IQ tends to approach their 'genetic expectation.' --- And all the above assumes something many do not seem aware of (based on a different thread). IQs in the developed world seem to have started to substantially decline with no viable convenient explanation. Environmental or educational conditions achieving diminishing returns are what we would like to believe, yet of course if that was the case we'd expect to see an asymptotic decline of growth approaching 0. Instead we are seeing an actual decline in IQ. [3] One conflicting bit here is that most evidence indicates this decline started happening sometime in the mid 90s. Prior to that IQs had been increasingly, though more slowly over time - but that decline of growth is to be expected. [1a] - https://www.statista.com/statistics/241530/birth-rate-by-family-income-in-the-us/ https://www.statista.com/statistics/241530/birth-rate-by-fam... [1b] - https://www.census.gov/topics/health/fertility.html https://www.census.gov/topics/health/fertility.html (the statista graph presents this data in a cleaner format - adding this as just a more reliable source than random internet site) [2] - https://en.wikipedia.org/wiki/Heritability_of_IQ https://en.wikipedia.org/wiki/Heritability_of_IQ [3] - https://en.wikipedia.org/wiki/Flynn_effect#Possible_end_of_progression https://en.wikipedia.org/wiki/Flynn_effect#Possible_end_of_p...

Joeri 8y ago
IQs in the developed world seem to have started to substantially decline with no viable convenient explanation. Maybe what's happening is that IQ has been declining for a longer time, but the gains in health and nutrition were offsetting the effect. An interesting variable to compare to is life expectancy, which is a proxy for health. Its growth in western countries has been slowing and in the US it has even started declining. Studies have shown a link between IQ and life expectancy. Those studies generally looked towards a reason why higher IQ would lead to higher life expectancy, but perhaps the causation is reverse.
- AstralStorm 8y ago
  We do not even have good enough data to support IQ results in a single generation related to this... (there are problems when checking across cultures) Additionally, the tests were modified over time. Is the reaction test the same? Was it checked for reproducibility? Has an alternative hypothesis of slower muscle speed been excluded? So, drawing any conclusion from these numbers is very, very risky, even riskier over time - unless you somehow invent time travel and give Victorian era people the exact same test we give people now. Remember, IQ tests are graded across average in a generation...
  - TangoTrotFox 8y ago
    One standard measurement of IQ is the Stanford-Binet exam. It's been around since 1916 with extensive concern given to consistency in the 5 updates it has received over the century. And that consistency is determined through thousands of trials with demographically representative samples to avoid predictable issues like a self selection bias in testing. But like you mention the tricky part is that IQ is measured across an average in a generation. The mean is normalized to 100 with a standard deviation of about 15 points. An IQ of 115 does not mean you 'scored' 115 in a vacuum, it means you performed better than 84% of people. The idea that IQ would substantially increase or decrease for an entire population over very short periods of time (thus changing the meaning, in a vacuum, of e.g. 115 IQ over short periods of time time) was surprising, and that's precisely what the Flynn Effect [1] is. However that change is precisely measurable and enables researchers to produce comparable values between generations. [1] - https://en.wikipedia.org/wiki/Flynn_effect https://en.wikipedia.org/wiki/Flynn_effect
SomewhatLikely 8y ago
Re: correlation of income to fertility. The causation could perhaps go the other way when looked at as potentially genetic preference for smaller families. Smaller families mean children receive a larger percentage of their parents' time and money which will give them an advantage over children whose parents divide their resources among more children. Of course effective birth control is still so new that it throws a wrench in this argument.

Joeri 8y ago

IQs in the developed world seem to have started to substantially decline with no viable convenient explanation. Maybe what's happening is that IQ has been declining for a longer time, but the gains in health and nutrition were offsetting the effect. An interesting variable to compare to is life expectancy, which is a proxy for health. Its growth in western countries has been slowing and in the US it has even started declining. Studies have shown a link between IQ and life expectancy. Those studies generally looked towards a reason why higher IQ would lead to higher life expectancy, but perhaps the causation is reverse.

AstralStorm 8y ago
We do not even have good enough data to support IQ results in a single generation related to this... (there are problems when checking across cultures) Additionally, the tests were modified over time. Is the reaction test the same? Was it checked for reproducibility? Has an alternative hypothesis of slower muscle speed been excluded? So, drawing any conclusion from these numbers is very, very risky, even riskier over time - unless you somehow invent time travel and give Victorian era people the exact same test we give people now. Remember, IQ tests are graded across average in a generation...
- TangoTrotFox 8y ago
  One standard measurement of IQ is the Stanford-Binet exam. It's been around since 1916 with extensive concern given to consistency in the 5 updates it has received over the century. And that consistency is determined through thousands of trials with demographically representative samples to avoid predictable issues like a self selection bias in testing. But like you mention the tricky part is that IQ is measured across an average in a generation. The mean is normalized to 100 with a standard deviation of about 15 points. An IQ of 115 does not mean you 'scored' 115 in a vacuum, it means you performed better than 84% of people. The idea that IQ would substantially increase or decrease for an entire population over very short periods of time (thus changing the meaning, in a vacuum, of e.g. 115 IQ over short periods of time time) was surprising, and that's precisely what the Flynn Effect [1] is. However that change is precisely measurable and enables researchers to produce comparable values between generations. [1] - https://en.wikipedia.org/wiki/Flynn_effect https://en.wikipedia.org/wiki/Flynn_effect

SomewhatLikely 8y ago

Re: correlation of income to fertility. The causation could perhaps go the other way when looked at as potentially genetic preference for smaller families. Smaller families mean children receive a larger percentage of their parents' time and money which will give them an advantage over children whose parents divide their resources among more children. Of course effective birth control is still so new that it throws a wrench in this argument.