sudanglo:You start to understand how your own language works once you start studying foreign languages

I have learned so much about English from spending time around non-native speakers and also from trying to learn other languages.

For example:
I don't know why that is.
I don't know. Why is that?

We switch the that and is when we ask a question versus when we make a statement. I never realized this until seeing the structure of other languages.

sudanglo:

You start to understand how your own language works once you start studying foreign languages

This seems to me a view which is often expressed to support the learning of foreign languages. But I am not convinced.

How many native English speakers who have learnt Esperanto are equipped to explain the real difference between Have you seen and Did you see, because they have learnt Esperanto.

Or how does learning of French reveal the meaning of 'will' (as an auxiliary verb) and what idea is being expressed in 'I am seeing John tomorrow' versus 'I shall see John tomorrow'.

What learning foreign languages can do is reveal potentially ambiguity in your mother tongue, because the foreign language may require two separate translations. So it becomes apparent that a particular sentence in your own language may embody two different ideas. (Esperanto is particular strong in that regard for native speakers of English.)

But that is quite different to understanding what concepts underlie the grammar of your mother tongue and bringing those to consciousness.

If the foreign language confounds what your own language expresses separately, I suspect you learn nothing (except for a certain contempt for the foreign language unable to make the distinction).

I see where you are coming from, but I'd argue that in the case of a monolingual person with no idea what a present perfect or simple past tense is in any language is at a far lower level of understanding than someone who has a perfect understanding of them in a second language. ("Cxu vi estas vidinta" versus "Cxu vi vidis" )
Although there are those cases with no equivalents or even worse with false similarities (like gerunds and present progressive, etc.). These shouldn't be overlooked when considering this issue, but then I'd even say that knowing how to classify parts of speech and understanding the workings of grammar in general is very helpful to understanding any language.

Speaking from personal experience I learned more about grammar in Spanish classes than in English classes. I think seeing the same ideas re-hashed in a different (and to me more intuitive way) made the concepts click in my mind. My understanding of grammar from English classes was very rudimentary at best, and I still find myself thinking of Esperanto when I am unsure of whether I am using correct English grammar in some instances (vs. "colloquial grammar" ).

The acquisition of language is not a "one-on-one" concept. We cannot specify why understanding that the word for a four-legged creature that barks should be called chien, Hund, or perro - but we can understand that these names are not related to the object that they signify - they are arbitrary signs for the signified. Just understanding that concept helps the learner relate to her/his mother language and the way that signs and signified relate.
Also understanding that "do you prefer cake" does not translate into Spanish as "haces tu preferir pastel" or "ĉu vi havas preferi kukon" en Esperanto, but that rather each language has its own way of formulating utterances, is a revelation. I therefore full-heartedly agree that studying Esperanto indeed fulfills the goals of studying a foreign language for furthering educative inquiry in a student.

I am of the US, and unlike some here, perhaps, I myself very strongly support an "official English" approach for this country. You might call me a "melting potist." When my ancestors (and a now deceased dear friend) came to this country they learned English. They did not expect others to accommodate them in their own languages, and they did not expect to retain all of their own culture. They were going to be Americans, which meant learning English and joining the dominant (English speaking) culture.

However, at the same time I am a strong, strong supporter of the ideal of a common language which is nobody's private language, just as Zamenhof envisioned for Esperanto. I would be quite happy to see Esperanto (or whatever constructed auxiliary language) widely taught throughout the USA -- and the world -- as a common tongue for dissimilar communities, still keeping English (here) as the official national language. Unfortunately I do not see that happening here in my lifetime (which will be only a few more decades at most, anyway).

bartlett22183:I am of the US, and unlike some here, perhaps, I myself very strongly support an "official English" approach for this country. You might call me a "melting potist." When my ancestors (and a now deceased dear friend) came to this country they learned English. They did not expect others to accommodate them in their own languages, and they did not expect to retain all of their own culture. They were going to be Americans, which meant learning English and joining the dominant (English speaking) culture.

That's all fine and good, but what about the Native Americans who were here first and got English imposed upon them. Or the people living in the Southwest (who were Spanish speaking) who maybe didn't consent to being annexed into the United States? What right do English speaking usonanoj have to tell these people, "hey, you're Americans now (even though you didn't actually go anywhere), so give up your language and learn English." If you came here of your own volition I can see it. But if you were annexed, you should have the right to use your language and have your language used to you by the government.

Now we're getting into the whole idea of imperialism, which Esperanto was made to prevent.

It's not much of a diverse pot if one ingredient is vastly more prevalent than the others.

Robb, understanding that foreigners do it differently, and they are not just speaking English in a foreign language, does not per se reveal the mechanisms of one's mother tongue.

In learning a foreign language you learn a different system. But it requires an extra leap of logic to the conclusion that this makes conscious in the student the previously unconscious knowledge of his own language.

You might just as well say that learning to roller skate makes explicit the skill of walking.

I believe in Universal Grammar a la Chomsky. I do believe from my observations with many, many language learners that the UG does not just fade away with age. It was in tapping into my own UG that I became aware of deep structure, a deep structure that underlies all human speech. The problems faced by most who study another language is that they get caught up in idomatic expressions in both the L-1 and L-2 (source language and target language, if you will). The first step for serious language learners is to be able to discern between the trappings of expression in one language, filter out the information that is to be transmitted, and then recoding it into a new system.
It seems that many people don't see their own language system for what it is. E.g., English speakers have litte or no understanding of "do-fronting" though they use it all the time. Once they understand that "do-fronting" is an English idiosyncracy they can go beyond. Good English speakers "fight" with the urge to shift tonic stress in the target language. When I watch BBC news I always get coniptions when they pronounce Japanese place names. Americans do poorly with foreign proper names but the Brits really take the cake (e.g. h'rOshema). It is only that they are not aware of other phonetic systems. If they were, they would adapt their speech accordingly to be more internationally intelligable.
That is why Esperanto is so nifty in Foreign Language instruction. There are few idiomatic expressions and a sound to sign relationship that is fairly straight forward. The morphology is also fairly straight forward. Once the learner becomes aware of a differing phonetic, semantic, syntactic and morphological pattern per se, then she/he can apply that to other languages.

robbkvasnak:I believe in Universal Grammar a la Chomsky.

OMG! OMFG! I AM NOT ALONE!

Seriously, Robb, you made my day.

I believe in Universal Grammar

What is meant by Universal Grammar?

A grammar is a description of the rules governing the composition of clauses, phrases, and words in a language. It is implausible that an elegant and economical grammar of one language is going to fit another language.

Rules can be very different in different languages. The rules of cricket won't do as a description of football.

What place would Esperanto's accusative of direction and time have in a description of English. What place would the (six?) different ways of talking about the future in English have in an account of Esperanto?

Maybe at some level of abstraction (if you try hard enough) a grammar could be produced which fits all languages. But again this seems implausible, and such a grammar likely to be very unwieldy and of little use to a language learner.

If Universal Grammar is a neurological hypothesis - that circuits in the brain for language processing operate in a similar way in all human beings, regardless of their mother tongue - then this is pure speculation, given our current state of knowledge about how the brain works.