Color me skeptical. Pretty much every intervention ever tried has failed to measurably increase IQ long-term. The only exceptions are fixing nutritional deficiencies. If you could reliably raise IQ by a standard deviation in reasonably nourished children, it would be one of the most profound socio-political developments of all time (on the scale of major economic transitions like agriculture -> manufacturing -> knowledge work).

Well average IQ of the human population around the world has been increasing in the past decades if not centuries. And it's not because we're evolving within a few generations.

There's been really interesting work showing correlations between this increase in IQ and improvements in diet.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3044837/

IQ of groups around the world have been improving, but the composition of groups has changed.

Eg Africa went from 1/2 the population of Europe in 1950 to 1.6x the size today.

Minor nitpick. I understand what you're saying but average IQ is by definition 100 (with a deviation of 15). The scale itself moves, e.g. new 100 would usually be more than 100 in previous iteration of the test [1]

[1] https://en.wikipedia.org/wiki/Flynn_effect

There have been massive improvements in average nutrition over the last few decades though.

Your parent is right: IQ has been increasing. Even in countries where you wouldn't expect the cause to be improved nutrition. But nobody really knows why, nor has anybody discovered an intervention that can, on its own, reliably increase IQ.

Not only nutrition, but overall childhood experience is getting better worldwide. Even in countries that had no malnutrition, there was a lot of space to improve in children<->parents relationships etc.

Meanwhile some countries that were really good in all areas a while ago are now reporting minor IQ decrease..

I certainly studied for a major IQ test, over the course of a week. Basically, I went online and did every free IQ test I could find. You start to learn the various tricks and patterns they search for, and my overall range of scores increased over time (though there was wild variance from test to test).

Ostensibly, given all the nebulous argumentation of what "intelligence" is, the only thing an individual IQ test concretely measures is how good you are at taking IQ tests. ;-)

when I got my first home PC in 1993 there was IQ test software on it. I took the test tired, drunk, happy, caffeinated, all sorts of ways. I had huge swings in the score . +- 40 points for me personally.

I came to the same conclusion as you - that it only ranks how well I can take an IQ test.

The abstract for your source covers only children. Is there evidence of the same claim in adults?

That article studied IQ gains in students aged 17 or younger. I’m a bit skeptical the same findings generalize to adults and older, but I’d shown otherwise with other studies/sources