Gender-based languages (particularly German)
Hey, I'm an avid duolingo learner and I'm trying to learn German on your system right now but consistently failing because I don't think the course as is does a very good job of isolating the genders.
I don't think you should necessarily change any of the present skills, but could you add three skills in a row somewhere near the early middle where you just barrage learners with a bunch of masculine nouns, a bunch of feminine nouns, and a bunch of neuter nouns, respectively? Learning them all together will do wonders to actually conceptualizing the objects inside as masculine, feminine, and neuter things.
Sapir-Whorf has been widely criticized by many, but one area where the two really struck a chord that has been replicated multiple times is the fact that speakers of a given language where its objects have a grammatical gender consistently describe objects associated with a certain gender in masculine, feminine, or neuter terms respectively. If you really want to teach the genders well (this goes for German but could really be applied in any gendered language, which I would also appreciate because I am learning most of them), consider making the sentences in the three skills I'm suggesting use consistent semantically masculine/feminine/neuter adjectives and verbs to really embed the concept in the user's mind.
Let me know what you think. At the very least, I know I would benefit a ton from this while using your system.
Could anyone who has studied linguistics give a simple explanation why on earth have genders of nouns developed at all in several languages? I can fully understand cases of nouns - because cases convey additional meaning. But genders add just complexity without any positive side.