We haven't chosen to teach any foreign languages to our children. Our older son dabbled in Spanish for a while but his interest fell off, and we didn't insist that he continue.
If a very young child of mine has a finite capacity for learning new vocabulary, as well as limited time resources spent on that, I'd actually prefer that this learning be in the primary language, since one would naturally tend to learn the basic words of everyday life before more advanced terms. This hopefully leads to the ability to discuss more complex and abstract topics early on, instead of simply learning duplicate words for the same thing but in different languages. Instead of hoping for a generalized cognitive benefit from learning extra languages early, I'd rather my children learn one language deeply to directly enable higher-level learning, discussion and thought.
I suspect that the D'Souza woman from the article is deluding herself when she attributes enhanced math and science ability to her choice of extra foreign languages for her children. It might be true, but there's no way she could know it to be so, and I'm skeptical until I see some actual evidence.
I'm also guessing that many gifted people, at least the verbally gifted, would pick up languages much more easily than the general populace, at any age. That's true in my case, and I didn't learn my first foreign language at a young age.
