But an adult will never learn second languages faster than a child, and in fact will never learn a first language at all if not during childhood.
The same is true with sports. I imagine that if an adult has never learned to walk (somehow) that it would take a lot longer than a few months to learn to walk (a newborn doesn't take years to learn to walk...he/she takes years to build muscle strength, and then typically a short time to learn to walk and then immediately run).
I think we all wish McWilliams was correct...I just don't think he is.
will never learn a first language at all if not during childhood.
Pretty much true.
But an adult will never learn second languages faster than a child,
There's probably some fading of plasticity, but there's lots of other explanations too. Children learning languages are surrounded by it, and spend all their time learning it. Almost all adult language learning is part time, rather than full time immersion. Fluency in either case requires several years, but "can get by in" is plausibly shorter (weeks to months, say) for an adult learning se...
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