Yeah. I read it. I also read that it's all from germany, so anything that happened in just that country could have shaped the outcome that the study couldn't account for, and also that only about 150 people total responded back to filling out the questionnaire and returning it.

That it was a voluntary mailed out follow up sent out to thousands of people and only 150 responded back is a huge variable that goes into the question of "what type of people would respond back?"

So this headline is really wrong then. As IQ is measured relative to age, it's a lot easier to be slightly ahead of your peers as a kid, than it is as an adult.