If it's worth saying, but not worth its own post, then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should start on Monday, and end on Sunday.
4. Unflag the two options "Notify me of new top level comments on this article" and "
Languages I speak, in chronological order of starting to learn, are: Slovak, Hungarian, English, Russian, Esperanto. (Of these, Hungarian and Russian remain on the level of "I am able to read a text slowly, but I need to use a dictionary, and my vocabulary is so limited I can't speak fluently, and my grammar is horrible, but if you give me time to find the right words in the dictionary, I will be able to communicate the meaning.") So you could argue that more languages make learning another language easier.
However, after Esperanto I also tried learning Spanish, Japanese, and German, but didn't get very far. Of course, it's not like I spent the same amount of time and attention on each, so it's not a fair comparison. But I believe that if German would be as easy as Esperanto, I would be already speaking it fluently.
With regard to similarities, Slovak is similar to Russian, and I learned Russian 4 years at school, and read a few books. I spent much less time learning Esperanto.
I don't know how to compare difficulty of languages, because different languages are complicated in different ways. For example in English there is the complicated pronounciation, and irregular verbs. On the other hand, German has gramatical genders, and declination. Not sure which one of those is more complicated. Slovak and Russian have probably the same kind of complexity as German, only worse. Hungarian seems mostly regular, but has the definite vs indefinite verbs (not sure I am calling that properly).So, it seems like natural languages evolve complexities in different places.
I suspect there might be a "law" that keeps complexity of languages within certain limits: too complicated languages become difficult to speak properly, so some parts get simplified, but beyond certain level the knowledge of the complexities of language becomes a matter of signalling (the smarter and more educated people are more likely to get those complexities right), which creates a social pressure against further simplification. For example, in Slovak langauge we have two letters that are pronounced exactly the same ("i" and "y"), the reason for having them is historical: thousand years ago they were pronounced differently. Children spend a lot of time at school learning proper rules which one of these letters should be written in which situations; the rules are complicated, require memorizing long lists of word roots, and you still have many exceptions afterwards. But proposals to simply use one of those letters and just forget the other one are met with horrified reaction "but that would seem stupid!"; i.e. today the ability to write "i" and "y" properly is perceived as a signal of intelligence and education, so writing "i" everywhere pattern-matches being stupid and uneducated. And of course we wouldn't reform our language towards a state that feels stupid for us today. Essentially, wanting to remove a useless complexity makes you seem like complaining that you are too stupid to memorize it properly.
Yes, but it wouldn't work in the opposite direction: I would not understand when someone else says "visible"... or "audible", or "comprehensive", etc. But in Esperanto I can often understand words I never heard before, such as "see-able", "hear-able", "understand-able", simply because I am already familiar with the root and the suffix.
This happens very frequently in Esperanto, because even words that would be considered "obviously independent" by an English speaker are considered "related" by an Esperanto speaker. An example that horrifies many people are opposites: instead of "dark" you say "un-light", instead of "short" you say "un-tall". With this simple hack you have removed a need to learn hundreds of words. There are more such hacks; instead of "knife" you say "cut-tool", instead of "hospital" you say "un-healthy-person-place". Nouns / verbs / adjectives / adverbs differ by the last letter, so you don't need to learn "fast", "speed", "quickly", and "hurry" as four independent word roots; and instead of "accelerate" you say "make-more-quick".
This is probably difficult to get across, because when I just use "see" and "visible" as an example, you probably feel like "yeah, so there is this one weird example, but there still remains 99.99% of the language to learn". But Esperanto is more like taking a language and throwing 75% of words away because they can be derived from other words, and making the remaining 25% regular. So with the same energy you would learn 100 English words you can learn 150 Esperanto words (because they are more regular), which you can start putting together like a Lego and create maybe 1000 Esperanto words. Realistically speaking, you are not going to do this systematically, so it will feel like you only know 150 Esperanto words, but there are the potential 850 other words that you don't know you know, but when you meet them for the first time, your brain goes "oh, I actually know what this means".
(By the way, the composed words are usually not too long, because the common prefixes and suffixes are typically monosyllabic. Or, as an Esperanto speaker would say, "one-syllable-y".)
Some of them are raised bilingually, with Esperanto as a second language; but some of them are actually trilingual, coming from mixed marriages where parents use Esperanto to talk to each other. They are very rare, and I have no idea which model is more frequent.
I agree that this is quite likely. Maybe it wouldn't happen under the "Esperanto as everyone's second language" scenario, but it certainly is a risk with the "native speakers". (And various signallers, who believe that Esperanto needs more word roots because it e.g. allows better poetry. Sigh. Priorities.)
EDIT: In another comment, you say how Esperanto is much easier to learn for a French speaker than for e.g. a Tamil speaker. That is certainly true. But if you give the Tamil speaker a choice between learning English and learning Esperanto, in both cases the language will be completely unfamiliar, but in one case there will be the advantage of greater regularity and "Lego system". So while the Tamil speaker would complain that speaking Esperanto gives an unfair advantage to the French, they would still prefer Esperanto to English (if the advantages of learning either language would be the same, which is obviously not the case.)
This is actually an objection frequently made against Esperanto. People are familiar with the concept of "some languages are similar to each other, some are completely different", but unfamiliar with the concept of "Lego languages are much easier to learn", so of course they are going to attribute everyone saying "Esperanto was easy for me" fully to the former. Yes, it plays a role, but the regularity also plays a role. Esperanto has also fans outside Europe/America.
(I don't have much I want to say in response to this, but want to note that I read it and found it interesting and insightful.)