I have a theory. It is based on my observations only. There is nothing scientific behind it.
The human brain is like a sponge. A sponge can absorb water many times its weight. But eventually the sponge gets full and can not absorb any more. Once full, every drop that is added causes another drop to drip out.
The human brain is similar to a sponge. It can absorb all sorts of knowledge, but eventually it gets full and for every new thing that is learned, something is forgotten.
This brings me to China. My theory is the Chinese language is so complex that it takes up an inordinate amount of space in the brain when compared to the Romance languages. Since the language is used every day, it is seldom forgotten. Thus people who speak Chinese have fewer brain cells devoted to non-language knowledge.
This explains much of the distinctive Chinese behaviors, customs, and methods of doing things that don’t seem to make sense to westerners.