3 ms·

A lot of interesting hypothesis in this thread. But I’ll offer the simplest, and unfortunately least optimistic: This is simply downstream of the Flynn effect.

A lot of interesting hypothesis in this thread. But I’ll offer the simplest, and unfortunately least optimistic: This is simply downstream of the Flynn effect. There were serious gains in IQ between the cohort aging into Alzheimer’s 30 years ago and today. This was mainly due to improvements in childhood nutrition, healthcare, and education in the post war period. It’s well known that Alzheimer’s rates tend to be much lower in the high IQ. Not because the incidence of disease is lower, but because it’s harder to diagnose. John von Neumann would have to experience some serious mental decline before he started failing the standard cognitive batteries. This is less hopeful for two reasons. Number one the disease still exists and is having an effect. It’s still bad if you experience mental decline even if you start at a high baseline. And if life extends far enough, eventually it will get you in a real bad way sooner or later. Number two IQ gains, like height, started seriously after this cohort. So we wouldn’t expect to see continued declines at the same rate.

kqr 5y ago
This is a good point. As the traditional wisdom goes: when your data indicate a signal, first suspect the validity of your data.
alexgmcm 5y ago
>Not because the incidence of disease is lower, but because it’s harder to diagnose. While it's seems true that "High IQ can mask early Alzheimer’s symptoms"[1] I would be surprised if that could explain such a large decline in incidence as they mention in that report that while it did mask the early symptoms, that just made the decline appear more sudden. The cognitive decline is really incredible, I saw it happen to my grandmother and she went from being a perfectly normal person to not recognising family members and becoming increasingly confused and aggressive all within a few years. So I think even more educated/intelligent people would eventually be diagnosed (perhaps a few months later) and thus any effect on the incidence would be small (due perhaps to these people dying prior to diagnosis). Furthermore, the Flynn effect is quite small, no - around 14 IQ points over more than half a century and now some talk of a decline, the "reversed Flynn effect" so it's not even clear how substantial an IQ difference we could expect. If the decline is due to "improvements in childhood nutrition, healthcare, and education" then I think that's quite good though, as those are things we can control. [1] https://www.heraldnet.com/news/high-iq-can-mask-early-alzheimers-symptoms/ https://www.heraldnet.com/news/high-iq-can-mask-early-alzhei...
rendall 5y ago
> This was mainly due to improvements in childhood nutrition, healthcare, and education in the post war period. Even controlling for these improvements, the Flynn Effect is still happening. The cause of the Flynn Effect is as-yet unknown, but it is not due to these improvements. There's speculation that it's due to society increasingly being an environment that develops abstract thinking, which is the kind of thinking that is tested in IQ tests. So it's not that people are organically developing a higher IQ, but that people are just getting better at IQ tests

kqr 5y ago

This is a good point. As the traditional wisdom goes: when your data indicate a signal, first suspect the validity of your data.

alexgmcm 5y ago

>Not because the incidence of disease is lower, but because it’s harder to diagnose. While it's seems true that "High IQ can mask early Alzheimer’s symptoms"[1] I would be surprised if that could explain such a large decline in incidence as they mention in that report that while it did mask the early symptoms, that just made the decline appear more sudden. The cognitive decline is really incredible, I saw it happen to my grandmother and she went from being a perfectly normal person to not recognising family members and becoming increasingly confused and aggressive all within a few years. So I think even more educated/intelligent people would eventually be diagnosed (perhaps a few months later) and thus any effect on the incidence would be small (due perhaps to these people dying prior to diagnosis). Furthermore, the Flynn effect is quite small, no - around 14 IQ points over more than half a century and now some talk of a decline, the "reversed Flynn effect" so it's not even clear how substantial an IQ difference we could expect. If the decline is due to "improvements in childhood nutrition, healthcare, and education" then I think that's quite good though, as those are things we can control. [1] https://www.heraldnet.com/news/high-iq-can-mask-early-alzheimers-symptoms/ https://www.heraldnet.com/news/high-iq-can-mask-early-alzhei...

rendall 5y ago

> This was mainly due to improvements in childhood nutrition, healthcare, and education in the post war period. Even controlling for these improvements, the Flynn Effect is still happening. The cause of the Flynn Effect is as-yet unknown, but it is not due to these improvements. There's speculation that it's due to society increasingly being an environment that develops abstract thinking, which is the kind of thinking that is tested in IQ tests. So it's not that people are organically developing a higher IQ, but that people are just getting better at IQ tests