[X4]

Fully agree with jerf on that, adults not only have the mental barrier, but also their mental adaptivity ratio is lower than that of kids. I am not sure, if it's just the neural plasticity that's reason for this or the amount of neural circuitry's rewiring that is necessary at a higher age, due to more synaptic connections.

I mean chinese parents who teach their kids to learn many languages, maths etc. at age 1 and up may be cruel, but if they actually don't force the kids, but let them have fun and let them do those tasks voluntarily, then I fully support the early education method.