Depends on if you are "truly" bilingual. Only "truly" bilingual people can think in both languages. Many that speak more than one language are not truly bilingual in this sense. I do think the truly bilingual have advantages in how they think and perhaps concentrate...but it isn't necessarily the edge one might hope as there are many factors involved. I would say it could perhaps help a pool player.
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Just curious: what is the basis for saying you have to be able to think in both languages to be truly bilingual? I'm pretty fluent in Spanish -- taught by my parents and having lived outside of Madrid for three years -- but I've never thought in Spanish. Still, I'd consider myself bilingual.
Lou Figueroa