Sky, I like this idea. I think you’re saying that in learning a second language, we actually notice syntactic patterns. With the first language, we learn entire expressions more than generative rules. If this is the case, sampling another programming language would make us more fluent.

If I were shooting from the hip, I would think that learning Esperanto before French would better enable one to see where the language structure intersects. That is, what parts of learning a language are really fundamental rather than specific to a given language. If you were just learning French and someone gave you a grammar rule, it would be harder to know if the rule was some specific, arbitrary thing as opposed to an intuitive ‘natural’ extension of building a language. What the two languages have in common is more likely to be fundamental to building a language, and that is the only thing that would be reinforced by learning both languages. (Apart from the meta-data that is associated with the learning environment.)

You’d expect to get the same thing with programming, even though programming is a different kind of thinking. We don’t build programming languages by starting with monstrously complex things and trimming them down, we start with small ideas and build up. Thus, where languages share common features, those features are more likely to be obvious or intuitive methodologies for constructing the languages, and a bigger part of the core of what problems the language structure is designed to solve.