I agree with all that Risto says below.
Do want to add some thoughts.
“Ease of learning” will greatly depend on what is meant by learning. There are degrees and fields of many sorts in the learning process.
The issue of Indo-European vs. non-Indo-European is so often trivial.
There is great variance among Indo-European languages, even among those that are typically used for the raw material of IAL’s.
Moreover, “learning” to read/write will depend on what one wishes to read or write. Nobody ever learns everything. Do you want to converse online without any major error or misunderstanding? Or without any reference to things like dictionaries or spellcheckers? Do you want to be able to write legal contracts? Novels? Do you want to be able to write learned articles that will be accepted in scientific journals?
Grammar/syntax may play a role in ease, regardless of language group. If you speak a certain type of SOV language, you may find a similarly structured one easier, though it comes from the ends of the earth. The issue of Indo-European vs. non-Indo-European is not involved; Nepali is not structured like Norwegian.
Spoken language has its variables and registers. Do you only want to speak well enough to go shopping, or to order at a restaurant? Or do you want to do important business during a conference call?
Learning to speak will also depend on how well one wishes to be taken for a native speaker, and what sort of native speaker. A German agent parachuted into Britain during World War II would have to be very proficient, and in the right dialect.
The issue of Indo-European vs. non-Indo-European has little meaning in respect to comparative pronunciation patterns. Danish and Dhivehi do not have the same phonemes.
A speaker of Indonesian is likely to find Italian less difficult to pronounce than a Japanese would find Italian. An Italian is likely to find Russian more difficult to pronounce than he/she would find Japanese. Japanese often have a great deal of trouble pronouncing Chinese, but find less trouble with Malay, or even many Indo-European languages.
In my opinion, this adds up to the fact that the simple issue of Indo-European vs. non-Indo-European is not going to teach us much here.
Regards to all, Leo Moser
25.6.2014 19:14, Jeffrey Brown wrote:
Truly, all I want is to find any experimental evidence that Esperanto (or any other Euro-auxlang) is easy (or easier) than Euro-natlangs for non-IE speakers.
Ease of learning a language depends on many things, including teacher, learning materials, learning environment, and learners themselves. All of these variables should be somehow controlled in a proper scientific experiment to compare two languages.
Anecdotal evidence is interesting, but not valuable from the scientific point of view. Consider my testimony for example, maybe I found Esperanto difficult in some places because I didn't have a teacher or peer learners. I used a "teach yourself Esperanto" kind of book alone. It's a bad way to learn to speak any language.
Ease is a subjective thing. However, in addition to subjective variables, ease also depends on some objective variables. One of them is simplicity of the target language. I believe it is fair to say that Esperanto is objectively simpler than any Euro-natlang. Therefore we can conclude that, all else being equal, it is easier to learn Esperanto, which is simple, than Euro-natlangs, which are complex.
Unfortunately in reality all else is never equal. There are more and better teachers, books, video, audio, immersive environments etc for learning natlangs than Esperanto or any other constructed IALs. It is a huge disadvantage for conIALs.