3 ms·

Could it have other causes such as pollution, PFAS, microplastics, hormones in the water supply, less physical exercise (which is linked to brain growth) …?

by Tepix 4y ago

eesmith 4y ago
Remember this paper is only one data point. It even points out that: > These results are directly at odds with the differences of 0.20 to 0.33 SD per decade observed by Flynn, 1984, Flynn, 1987, Flynn, 2007 and the 0.15 to 0.195 SD per decade observed by Trahan et al. (2014), where more recent norming samples had higher IQ scores It may well be that the variability in this sort of analysis is too high to say anything. Not only is there the well-known problem that "intelligence" isn't easy to measure (and different tests give different numbers), but also people don't always make the same effort at doing the tests. If there's a secular trend to not caring about these tests then the numbers would likely go down. (Call it "Facebook quiz burnout. :) The paper then goes on to say: > these findings are consistent with studies that have found a reversal of the Flynn effect (Dutton and Lynn, 2013, Dutton and Lynn, 2015; Rönnlund et al., 2013; Sundet et al., 2004; Teasdale and Owen, 2008; Woodley and Meisenberg, 2013). Those studies are from Finland, Sweden, France, Norway, Denmark and the Netherlands, so if it's something like pollution then it needs to explain how that trend appeared in northern Europe even back in the late 1900s. I say "late 1900s" because I skimmed through the Sweden study ("Secular trends in cognitive test performance: Swedish conscript data 1970–1993" at https://www.sciencedirect.com/science/article/abs/pii/S0160289612001055 https://www.sciencedirect.com/science/article/abs/pii/S01602... ). It says: > Finally, evidence that the FE has ceased during the last decades has been provided in a recent set of studies. First, a study based on Norwegian conscripts revealed gains up to the mid 1990s after which a tendency of decline was actually observed until 2002 (Sundet, Barlaug, & Torjussen, 2004; cf. also Teasdale & Owen, 2005). ... > Finally, performance on Piagetian measures showed a decline corresponding to 4.3 IQ points per decade, over the years 1975–2003 in British samples (Shayer, Ginsburg, & Coe, 2007), suggestive of a reversed FE. Since pollution levels decreased by the end of the 1900s (more emissions control, no leaded gasoline, etc.), that broad category seems unlikely. Similarly, my knee-jerk thought was a cause might be the negative consequences of focusing on high-stakes testing in the US. But that can't explain any negative trends in Europe which started before "No Child Left Behind." But again, this might just be the sort of result you get from trying to analyze noisy data. Sometimes it's high, sometimes it's low, and your measurement tools are bear skins and stone knives.
- slowmovintarget 4y ago
  I'd bet on the underlying factor being nutrition. Processed foods, sugar substitutes, and forever chemicals in everything to an extent earlier generations never saw. But that's a wild guess.
  - eesmith 4y ago
    End of the abstract from that Swedish study at https://www.sciencedirect.com/science/article/abs/pii/S0160289612001055 https://www.sciencedirect.com/science/article/abs/pii/S01602... : > Finally, comparisons of trends in cognitive performance and in standing height show that the gains in cognitive performance over the years from 1980 to 1993 occurred in the absence of overall gains in height, which speaks against nutrition as the cause of the Flynn effects. Thing is, you can point to all sorts of changes. Perhaps it's more screen time, or any other pet peeve. From my cursory reading of those papers, there's no clear reason for the Flynn effect, nor its (putative) reversal despite lots of correlation studies.
DoreenMichele 4y ago
Despite Occam's Razor, I will suggest the answer could be both poor education and health issues of the sort you list.
pjc50 4y ago
The pandemic? Heck, even plain old mean reversion - the site mentions the Flynn Effect, an unexplained gradual increase in IQ scores; there's no guarantee that such an effect should continue forever.
- sokoloff 4y ago
  > From 2006 to 2018, the age groups measured generally saw declines in the IQ test used by the study I’ll wager it wasn’t the pandemic.

Could it have other causes such as pollution, PFAS, microplastics, hormones in the water supply, less physical exercise (which is linked to brain growth) …?

by Tepix 4y ago

Could it have other causes such as pollution, PFAS, microplastics, hormones in the water supply, less physical exercise (which is linked to brain growth) …?

eesmith 4y ago

Remember this paper is only one data point. It even points out that: > These results are directly at odds with the differences of 0.20 to 0.33 SD per decade observed by Flynn, 1984, Flynn, 1987, Flynn, 2007 and the 0.15 to 0.195 SD per decade observed by Trahan et al. (2014), where more recent norming samples had higher IQ scores It may well be that the variability in this sort of analysis is too high to say anything. Not only is there the well-known problem that "intelligence" isn't easy to measure (and different tests give different numbers), but also people don't always make the same effort at doing the tests. If there's a secular trend to not caring about these tests then the numbers would likely go down. (Call it "Facebook quiz burnout. :) The paper then goes on to say: > these findings are consistent with studies that have found a reversal of the Flynn effect (Dutton and Lynn, 2013, Dutton and Lynn, 2015; Rönnlund et al., 2013; Sundet et al., 2004; Teasdale and Owen, 2008; Woodley and Meisenberg, 2013). Those studies are from Finland, Sweden, France, Norway, Denmark and the Netherlands, so if it's something like pollution then it needs to explain how that trend appeared in northern Europe even back in the late 1900s. I say "late 1900s" because I skimmed through the Sweden study ("Secular trends in cognitive test performance: Swedish conscript data 1970–1993" at https://www.sciencedirect.com/science/article/abs/pii/S0160289612001055 https://www.sciencedirect.com/science/article/abs/pii/S01602... ). It says: > Finally, evidence that the FE has ceased during the last decades has been provided in a recent set of studies. First, a study based on Norwegian conscripts revealed gains up to the mid 1990s after which a tendency of decline was actually observed until 2002 (Sundet, Barlaug, & Torjussen, 2004; cf. also Teasdale & Owen, 2005). ... > Finally, performance on Piagetian measures showed a decline corresponding to 4.3 IQ points per decade, over the years 1975–2003 in British samples (Shayer, Ginsburg, & Coe, 2007), suggestive of a reversed FE. Since pollution levels decreased by the end of the 1900s (more emissions control, no leaded gasoline, etc.), that broad category seems unlikely. Similarly, my knee-jerk thought was a cause might be the negative consequences of focusing on high-stakes testing in the US. But that can't explain any negative trends in Europe which started before "No Child Left Behind." But again, this might just be the sort of result you get from trying to analyze noisy data. Sometimes it's high, sometimes it's low, and your measurement tools are bear skins and stone knives.

slowmovintarget 4y ago
I'd bet on the underlying factor being nutrition. Processed foods, sugar substitutes, and forever chemicals in everything to an extent earlier generations never saw. But that's a wild guess.
- eesmith 4y ago
  End of the abstract from that Swedish study at https://www.sciencedirect.com/science/article/abs/pii/S0160289612001055 https://www.sciencedirect.com/science/article/abs/pii/S01602... : > Finally, comparisons of trends in cognitive performance and in standing height show that the gains in cognitive performance over the years from 1980 to 1993 occurred in the absence of overall gains in height, which speaks against nutrition as the cause of the Flynn effects. Thing is, you can point to all sorts of changes. Perhaps it's more screen time, or any other pet peeve. From my cursory reading of those papers, there's no clear reason for the Flynn effect, nor its (putative) reversal despite lots of correlation studies.

DoreenMichele 4y ago

Despite Occam's Razor, I will suggest the answer could be both poor education and health issues of the sort you list.

pjc50 4y ago

The pandemic? Heck, even plain old mean reversion - the site mentions the Flynn Effect, an unexplained gradual increase in IQ scores; there's no guarantee that such an effect should continue forever.

sokoloff 4y ago
> From 2006 to 2018, the age groups measured generally saw declines in the IQ test used by the study I’ll wager it wasn’t the pandemic.