Do you have a prefered explanation for the Flynn effect?
The Norwegian military conscripts above were part of a paper suggesting an interesting theory I hadn’t heard before: that children are less intelligent as more are added to families, and so intelligence has risen as the size of families has shrunk.
My guess: different causes of the Flynn effect dominated at different times (and maybe in different places, too).
For instance, Richard Lynn argued in 1990 that nutrition was the main explanation of the Flynn effect, but Flynn has recently counterargued that nutrition is unlikely to have contributed much since 1950 or so.
Another example. Rick Nevin reckons decreasing lead exposure for children has made all the difference, but when I did my own back-of-the-envelope calculations using NHANES data for teenagers from the late 1970s to 2010, it looked like lead probably had a big impact between the late 1970s and early 1990s (maybe 5 IQ points, as average lead levels sank from ~10μg/dL to ~2μg/dL), but not since then, because blood lead concentrations had fallen so low that further improvement (down to ~1μg/dL) made little difference to IQ.
Shrinking families would likely be a third factor along these lines, maybe kicking in hardest in mid-century, bolstering IQs after nutrition fell away as a key factor but before declining lead exposure made much difference.
Edit, November 27: fixing the Richard Lynn paper link.
And these different trends would tend to be consistently upwards rather than random, because we are consistently trying to improve such things? (Though the families one would probably still be random)
I’m not sure we do consistently try to improve these things. Nutrition, yes. But lead exposure got appreciably worse between WWI and 1970-1975, at least in the UK & US, and shrinking families is a manifestation of the demographic transition, which is only semi-intentional.
Reading Steve Wozniaks biography iWoz I support your view that parents nowadays focus more on education in youngest years. Steve learned about electronic components even before he was four years old. His father explained to him many things about electronics before he was old enough for school. He learned to read at the age of three. This needs parents who assist. Steve Wozniak praised his father for explaining always on a level he could understand. Only one step at a time.
His exceptional high intelligence, he cited a test IQ > 200, is for sure not only inherited but consequence of loving care, teaching and challenging by his parents and peers.
There no good reason to think about this effect based on individual anecdotes. We do have controlled studies about the effects of parenting and it suggests that it doesn’t matter much.
You are right. I needed some time for reading. The Flynn effect documents long term rise of fluid intelligence. Parenting and teaching are improving predominantly crystalline intelligence.
Do you have a prefered explanation for the Flynn effect?
The Norwegian military conscripts above were part of a paper suggesting an interesting theory I hadn’t heard before: that children are less intelligent as more are added to families, and so intelligence has risen as the size of families has shrunk.
My guess: different causes of the Flynn effect dominated at different times (and maybe in different places, too).
For instance, Richard Lynn argued in 1990 that nutrition was the main explanation of the Flynn effect, but Flynn has recently counterargued that nutrition is unlikely to have contributed much since 1950 or so.
Another example. Rick Nevin reckons decreasing lead exposure for children has made all the difference, but when I did my own back-of-the-envelope calculations using NHANES data for teenagers from the late 1970s to 2010, it looked like lead probably had a big impact between the late 1970s and early 1990s (maybe 5 IQ points, as average lead levels sank from ~10μg/dL to ~2μg/dL), but not since then, because blood lead concentrations had fallen so low that further improvement (down to ~1μg/dL) made little difference to IQ.
Shrinking families would likely be a third factor along these lines, maybe kicking in hardest in mid-century, bolstering IQs after nutrition fell away as a key factor but before declining lead exposure made much difference.
Edit, November 27: fixing the Richard Lynn paper link.
And these different trends would tend to be consistently upwards rather than random, because we are consistently trying to improve such things? (Though the families one would probably still be random)
I’m not sure we do consistently try to improve these things. Nutrition, yes. But lead exposure got appreciably worse between WWI and 1970-1975, at least in the UK & US, and shrinking families is a manifestation of the demographic transition, which is only semi-intentional.
Reading Steve Wozniaks biography iWoz I support your view that parents nowadays focus more on education in youngest years. Steve learned about electronic components even before he was four years old. His father explained to him many things about electronics before he was old enough for school. He learned to read at the age of three. This needs parents who assist. Steve Wozniak praised his father for explaining always on a level he could understand. Only one step at a time.
His exceptional high intelligence, he cited a test IQ > 200, is for sure not only inherited but consequence of loving care, teaching and challenging by his parents and peers.
There no good reason to think about this effect based on individual anecdotes. We do have controlled studies about the effects of parenting and it suggests that it doesn’t matter much.
You are right. I needed some time for reading. The Flynn effect documents long term rise of fluid intelligence. Parenting and teaching are improving predominantly crystalline intelligence.