A few suggestions
Require users to correct themselves. I often just quickly hit enter twice in a row, to check answer and move on, expecting to get the question right. The problem is, I frequently get it wrong, but I don't get a chance to see what I did wrong, or to correct myself. If users were required to fix their mistakes before moving on to the next question, they would most likely not make the same mistake again.
(NO LONGER APPLIES WITH THE NEW UPDATES) Vary the given time for bonus rounds depending on difficulty/length of sentences. I get really frustrated when I am only given a minute for a bonus round with really long, difficult sentences, that takes me at least 2 minutes to complete. I think that different lessons should have different time limits for the bonus rounds.
The same sentence is often repeated too many times. I will often get the exact same sentence many times within each practice exercise, and then the bonus rounds, and the review. For example, I have seen "¿Qué tienes bajo el sombrero?" probably about 15 times within about 2 exercises and 2 bonus rounds. And, I have never gotten that particular sentence wrong. I can understand why a sentence might be repeated over and over again if a user kept getting it wrong, but I haven't been.
When users struggle with a certain word on a certain type of question, give them that type of question more, not just the word. If users struggle with a word only on a certain type of question - say for instance they have trouble recognizing the word when it is spoken - they need more practice with that specific aspect of the word. Duolingo will just give them more questions where they have to translate it either way, or they have to select it from a drop-down list. But if they only struggle recognizing the spoken word, that is what they need more questions with. Similar with any other forms of questions.
I continue to marvel at the elegance of duolingo. And while incremental improvement is good for all of us, I just wanted to express my appreciation for so excellent and versatile a language-learning application as it exists today, at the price it is provided, and without the distractions of revenue-generating ads. Simply, for me, WOW! And, THANKS!
I agree with all the suggestions, but I also know that the first is a well supported (i.e. in education studies) technique for reducing errors in writing, and therfore promotes more acurate learning. So that would be a priority. The fourth is less studied but also seems to help : using the same vocabulary with different sentences (or vice versa) will help extend learning to new contexts.
I don't hit enter twice. I look at it so carefully because I don't write anything down. Duolingo is fun for me because it's like a game. I don't want it to feel like school work.
I'd rather get it wrong a number of times until it's etched in my brain and then I'm sure I've learned it.
I agree very strongly with point number 3. I've already studied Latin, French and German elsewhere, so I have a proven record in learning languages. Once a phrase, a vocabulary word or conjugation is clearly mastered, endless repetition only wastes time which could be better spent making progress. I am extremely tired of ninas beben agua !!! (for instance) Checking back to see if material remains in mastery is a very good idea, but endless repetition of exactly the same phrases is simply BORING, BORING, BORING. However, I really appreciate the service Duolingo provides, and am grateful for the opportunity to learn another language. Thanks for that.
I also agree with all of the suggestions, especially #1 and #3. I am leraning french and it sometimes happens to me that the same sentence has to be tranlated up to three times within one exercise, sometimes even in consecutive questions. Repetition I think is necessary, but if the sentences vary slightly you have to concentrate more, which should have a biger effect than the repetition of exactly the same sentence. Nevertheless, I enjoy learning with duoling, never thought it would be so easy to learn another language without living abroad
One and Three are great suggestions. In the strengthen skills section it seems to just repeat seven or eight words and sentences over and over again. I would also recommend more translations from the language you know to the language you are learning - as it is a lot easier to pick out what it means without actually knowing how you would write or say it to someone.