I was thinking of someone who would be totally fluent in, say, two languages: for example, english (learned as a child ---> compulsory), and spanish (learned as an adult ---> by choice). When I say "fluent," I mean able to speak, read, and write in the language skillfully.
Under those conditions, the learning difficulties which, let's face it, we all experience as a child, could still leave traces in the mind years later when using one's primary language. The primary language would be associated with those frustrations that we all experience to some degree, while the secondary language might not.
I've heard from many people that after a second language is learned, it is relatively easy to learn a third and fourth language. This could be due to some blockage being overcome once more than one language is learned.
