Outside of environmental factors, social factors should also be considered.
Oversimplified:
Maybe everyone is being too safe and not exposing children to stimuli that promote better development.
I suspect several factors are contributing to this. 1) As more toys are discovered to be 'dangerous' or 'have small parts' children have less exposure to complex objects or it is deferred to later ages. 2) Adults have less, or are less inclined to, time to properly care for children and thus don't understand that judgement and supervision can allow 'supervised' use of toys that can be dangerous if not properly used, but would be fine if used while supervised. 3) I wonder how strongly this correlates to all parents within child rearing units being in the workforce (single parents, dual income parents, etc)? 4) Or how it relates to decreasing access to natural areas to explore as a child?
These are only some of the social influences that could also be part of the cause.
> 2) Adults have less, or are less inclined to, time to properly care for children
Rather the opposite, I suspect: the amount of time (well-off) adults spend tutoring, coaching, and otherwise interacting with their kids has gone through the roof in the past few decades.
When I was a kid (in Europe), both my parents worked. Starting in first grade, I walked to and from school unsupervised and was responsible for keeping myself entertained in the afternoons until they got home, which generally meant roaming the neighborhood with a pack of friends. This is pretty much inconceivable today.
I had the opposite upbringing, in that one of my parents was always home (at least until later in life when I was more self-sufficient); nowadays you can't seem to make ends meet or own a house unless both parents are working.
I mean I'm the age my dad was when his third child was coming and I was only able to buy a reasonable house last year. He / they were able to buy a bigger house, newly built, with more land on a single, low income wage and a 12.5% interest mortgage nearly 40 years ago.
"As Flynn and Shayer note, Scandinavian IQ declines might well presage future trends in other countries. It may be that, once we’ve made our schools as good as theirs, we’ll see our Flynn effect max out, and then whatever channels feed their anti-Flynn effect will show up in our data, too."
The summary of the study the article mentions and links to doesn't show if the trend is an average of some sort or if it's the result of a more self-selecting sample region.
Unfortunately between that and only having first-hand local culture knowledge, I am unqualified to speculate in a meaningful way about the differences in culture and environment.
Also, just because a trend is increasing does not also mean that there's an underlying masking effect or that there isn't overall convergence. Ideally at least similar studies would be performed on a global basis if a global comparison is occurring.
Oversimplified: Maybe everyone is being too safe and not exposing children to stimuli that promote better development.
I suspect several factors are contributing to this. 1) As more toys are discovered to be 'dangerous' or 'have small parts' children have less exposure to complex objects or it is deferred to later ages. 2) Adults have less, or are less inclined to, time to properly care for children and thus don't understand that judgement and supervision can allow 'supervised' use of toys that can be dangerous if not properly used, but would be fine if used while supervised. 3) I wonder how strongly this correlates to all parents within child rearing units being in the workforce (single parents, dual income parents, etc)? 4) Or how it relates to decreasing access to natural areas to explore as a child?
These are only some of the social influences that could also be part of the cause.