Lessons from a 7 (well, 8) language polygot
I think the reason many users are on Duolingo is to be able to speak multiple languages.
This guy speaks 7 language, and ASL (American Sign Language).
Here is a TEDx talk (in English) https://www.youtube.com/watch?v=_yhnWnR1g7M
And an AmA (Ask me Anything) on Reddit: http://www.reddit.com/r/IAmA/comments/y70v0/by_request_i_ama_polyglot_multilingual_person/
TL;DR: The guy says he has a poor memory, had trouble in school to learn languages but then easily learned multiple languages when he tried USING the languages with others.