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Improvements in Skill Strength

Over the past few weeks, we've been testing an improved version of the mathematical model that determines the strength ("goldness") of your skills. So far this experiment has been running on 50% of users, and the results look very promising, so today we've started running it for all users.

In the experiment, we attempt to determine which word(s) you're having trouble with based on your answers. As an example, if you're asked to translate "Yo soy una mujer" (which means "I am a woman") from Spanish into English, and you type "I am a girl", we will infer that you've forgotten the meaning of "mujer" but that you still know what "Yo", "soy", and "una" mean. We use this information to update the strength of your skills more accurately, based on the words that each skill teaches.

Going forward, this change should make it easier to keep your skills at full strength. On the other hand, it may slightly reduce the current strength level of some of your skills. We apologize if you are surprised, and appreciate your understanding as we continue trying to make Duolingo the best it can be.

June 10, 2015



My tree has been destroyed lol. Over 50 skills need strengthening, I'm going to need a 2 liter bottle of Mountain Dew and a bag of Doritos to take care of this.

My fluency seems to have improved though, I'm at 50% now and I think I was at 48% or 46% I don't remember ever being at 50%.


Your Mountain Dew and a bag of Doritos comment cracked me up. Here's a lingot to help you buy groceries :D


I wish my grocery store took lingots.


Me too. If I had a dollar for every lingot that I had, I'd be able to buy a lot of groceries!


My lingots would just about cover my summer Pimms requirements.


I could buy a return flight to Paris if my lingots were sterling!


Thank you very much!


My tree has a huge amount of color on it! Too bad this won't go back in time and re-anylize your answers and possible reduce my color on my tree!


Ya, that happened to me, I was at 27 and It boosted me up to 31!!


Somehow I was under the impression that it always worked that way. I'm curious though, if one got the sentence wrong in the past, did all the words in it get an increased decay rate?

Also in your example you specifically refer to a noun, what about a verb, what happens if you get the form "am" wrong, but "is" right? For example, I think there was a sentence in french that had something like "Je suis un homme, et elle est une femme". Or sentences where a particular word may be repeated and you get one right and the other wrong, e.g. Je suis un homme et je suis fort - I am a man and I is strong.

Anyway, this seems like a great improvement, but this post should be made into a sticky, in the past whenever such changes were made the next week or two we'd see numerous posts of people complaining about this.

P.S. Such announcements could probably be added to the tree itself, such as the tree change announcement.


That was also my first thought when I read this: "Didn't it already do that?"

Actually, because it is able to identify where your error was by crossing out that one word with a red line, I assumed it just knew which word you messed up and counted it.

It's like being told we took a step forward and realized we were actually standing five steps behind where we thought we were. I'm really excited about the progress, I was just under a very different impression.


Indeed, according to this post by tatou:

Many words get strengthened per session. When you practice, Duolingo targets your weakest words and gives you sentences for them. However, all words you see in those sentences are strengthened (not just the 9 or so we show at the end of the session). For example, if you practice the "Travel" skill, any words from "Basics" in those sentences will also get strengthened.

This new one may be more focused because it can actually test people immediately using the adaptive lessons rather than simply spitting random sentences to end the lesson. It can also conceivably fetch earlier sentences from other skills that use the word. Although that may not work well because of the different forms a word may take.


My guess is it decreased the strength of the word the sentence was made to teach, that is, the word it introduces in the skill. There are a minimum of the sentences per word.

In case you got the sentence right though, all the words were strengthened (still a guess), which is why you did not have to strengthen the first skills too often.


Thanks. This certainly sounds like it should be an improvement.


So, why is my tree still all gold? I`ll take the doritos, though. :-)


Same. It means we were in the 50% of people who already had this feature.


Or.... you just knew the material in your tree really well.


That makes sense. A few other thoughts:

Some time ago I realized that I wasn't doing as much learning the language as I was learning how to be a good duoLingo test taker. The modules facilitated this by giving away cues to the correct response versus allowing me to make learning decisions. This resulted in me being able to continually move farther along without actually learning what I was given credit for learning. I don't like being able to "cheat" this way, so here are my suggestions:

  • Always include the gender article with nouns in the word matching sections. Space is limited, yes, but I wouldn't mind scrolling through a short list to find the match. Doing this will help make repetitive areas more relevant. I'm sure I've never been wrong about the meanings of "orange," "phase," or other words that share the very same spelling and meaning in both languages. However, they keep being presented to me instead of the words that need learning. Including the article will at least let me learn that new part of a "known" word.

  • Related to the above... if they must remain capitalized, consider keeping word matching for nouns separate from other words. I do less learning when it's easy to pick off the noun match(es) because of the capital letter(s).

  • In the word matching sections, include two additional words that don't match. Once the last correct match is made, you automatically move to the next screen. Right now, I don't have to make a learning decision about the last two words, although I still have to tap them.

  • Don't capitalize non-nouns in the sentence assembly sections. This way, I really have to make a learning decision on sentence structure, which is one of my weakest areas. I know plenty of words, but need a better opportunity to understand how to assemble them.

Something else I've encountered:

  • I don't always understand why something is incorrect, so perhaps give a quick reminder on single wrong answers. For example, if I write "einen" instead of "einem," include a brief explanation like, "This gender article becomes 'einem' because..."

  • There have been times where I've tapped a word to get help, typed it, and then found a completely different word that wasn't on the list is the correct answer. Example: "My destiny." The help said it was either "Los," "das Schicksal," or "Schicksal." The correct solution was "Bestimmung." Don't know what to make of this.

Hope this helps, -Mark


Awesome reply & yes I agree with you.


Thanks for the info. I left the house with one skill to strengthen in Dutch, and came back with ten. This will probably help, eventually, though, but right at the start - ugh!


Thanks so much for the announcement. It was shocking, to be sure - but then seeing this somehow made it so much better. It makes all the difference when we get a "heads up" like this. Thanks so much for constantly working to make Duo better!

[deactivated user]

    5 minutes before the update: everything gold (1 tree and a half). After the update: 24 skills to strengthen. "Slightly".


    Luckily I went into Discussion before looking at my tree !! Would have been a bit better to get this message on a window prompt as soon as we connect to the site... To avoid a big shock... However I am looking forward to this improvement, sounds nice.


    Seconding this; it'd be nice to have a notification when a change like this is pushed out, something to clarify quickly that it's not some kind of error. I thought there might have been some data loss on the back end, or something!


    My tree turned into a colorful rainbow! Looks like I'm gonna be needing 2 bags of Doritos and maybe a Red Bull. Haha!


    This probably explains why it has been so easy for me to keep my Spanish tree shiny recently. Only 5 skills a week decay, very manageable, much more so than previously. Now if they could just work on tyop recognitiun.


    I appreciate this announcement (although not losing the last two hours of my life). On the other hand, when I left this morning, I was at 49 percent fluency, and then came back to 47. Strengthening all two dozen or so skills has not made it budge. Is this a casualty of the new algorithm?


    This sounds great. I really do just turn into a moron when dealing with some specific words & language features, so having duo pick up on those doesn't have an obvious downside.


    I logged in this evening to go "Dear Lord, what just happened to my trees?!"

    I think this is a great idea, but in the short term... yeep. Just a lot of work for me to re-gild my trees...


    Wow, my whole tree became golden.


    17 skills need strengthening :)


    Thanks for it ;)

    You are always making Duo better


    Thank you for this Improvement. Duolingo rocks!


    This is great and will improve learning in my opinion. I was considering asking for this feature as I had noticed that it didn't seem to recognize which part of the sentence was incorrect.


    Thank you for the update, I was a little confused when I logged on today and saw that my Swedish skills had gone stale at random, but not only does this clear that up but it is good news indeed. :)


    Yeesh... looks like I'm going to need to spend a day or two just regilding my trees, now...

    But I'll appreciate the change a whole lot more, once I've done that.


    I hope you will appreciate the change even more than you hope.


    You should also infer that they don't know the word for girl. You shouldn't ignore that. Thank you for the improvements.


    This sounds amazing and probably the best feature implemented since Duolingo for schools. I will definitely be actively learning German when I have time.


    I need to strengthen my tree to, I have been waiting for the flash cards, but I need to Stop being lazy and procrastinating all of my work. So, I guess I will start working.


    Sounds good. Thank you!


    Yep, don't have very much gold on my screen anymore.

    But sounds like a great plan, thanks. :)


    Time to clean up eleven previously gold trees (5 of them complete). :/

    edit: 203 skills total to strengthen. :(


    Oh. I got 27 Portuguese skills to strengthen today - instead of 2 or 3 that I used to get these days. I guess it's a sign to drop reviewing Portuguese and move on to Swedish, lol.


    For anyone who still has issues with Demonstratives 2 on French from English as I am now having, It has been officially confirmed that there is still an ongoing issue with that one leveling up to full level and is being looked into.


    Are you also considering hovering on the words for strength of knownledge? I often hover on words that I forgot the meaning and this means to me that it is a weak word, which should come again in the near future during exercises.


    Thanks for the information. I do not like the change, I do not have time to redo so many skills a day. My golden tree will become a color tree. For me this change is demotivating.


    It was a surprise, and not in a feel-good way, I'll give you that. But would you rather be falsely told "Wow, you're doing great!" or would you rather suck it up for a while and have the opportunity to really learn the language? It sounds like they're getting better at helping us focus on our weak spots.

    Maybe try just re-gilding 3 or 4 skills a day. It might be more manageable that way.


    I actually think that, in the long term, the change should make it easier to keep your tree gold. I was in the group that already had this feature (apparently, since nothing about my tree or my skills list has changed today), and I haven't had to strengthen a skill for weeks.

    I assume this is because any time I correctly translate a whole sentence, I've been getting credit for each individual word, and any time I incorrectly translate a sentence only a single word or two deteriorates.

    For this reason, when I use the "strengthen skills" button, it is almost always relevant to words I actually need practice with. I have never had to strengthen 'fille' or 'homme' or etc because I never get them wrong.

    I've been wondering why everyone else is always complaining that the strengthen skills button stinks or is irrelevant to their needs -- for me it's as precise as a laser. I'm glad that everyone gets to use the site this way now.


    I've had the same experience with my French tree lately. I've seen posts discussing "rapid tree degilding."

    I thought maybe my policy of "never look at the word hint or peak at its meaning" might have contributed to this, but this post's explanation makes sense, too.


    One of the problems with the strengthen skills button most recently has been that the skill level didn't actually strengthen on certain skills. When you hit the "strengthen skills" button, then did the skill exercise, the skill wouldn't strengthen. All in all though, I figure Duolingo's metrics are a work-in-progress. And I do like what all they offer...FOR FREE ESPECIALLY. So I'll keep working with them and hoping they work out the kinks.


    Depending on how many lessons a skill contains (and therefore how many words it covers) this may in some cases be unavoidable (if enough words are at the right level of weakeness, then to strengthen the whole skill you may need to do two or three skill strengtheners to cover enough of the vocab in the skill).

    Having said that—this current change is an excellent one because when you hit skill strengthen it should ensure that what you strengthen is chosen by the algorithm more efficiently. If so, then what your describing should happen less.


    Well, I hope this new effort does work. But as far as the redo of the skill strengthen button, it was glitchy, because others were having the same issue. What resolved it on the user level was to simply redo the whole exercise as if had not been done, then everything would strengthen and would stay at 5/5 or whatever the numbers would be for much longer. As I said, I'm willing to keep working the Duolingo's program and watch and see how things progress. They do offer a lot that's good.


    I can't see how what you're describing is a glitch. Some skills just require more work to strengthen because I don't know very well, or learnt quickly, or have made lots of mistakes on causing the words degrade quicker. That's the point of Duo's algorithm. By re-doing the skill you're—basically—learning more deeply material that the Duo algorithm thought you didn't know as well as you do other parts of the language.


    Sorry I'm very tired and my grammar in that comment was TERRIBLE.


    I just tried out one of the skills that had the issue and it's still the same, it doesn't increase even if I get more XPs. And it doesn't offer any other options but the same sentences over and over. This was one that many, not just I, were having issues with. If it offered other sentences, I could see where redoing it could benefit.


    My apologies, I had not understood you to have described the problem you perceive of repeating the same sentences.

    But, having said that, there's an issue of perception: How many times have you refreshed the skill? Are you sure that all the sentences are exactly the same?

    I completed the bottom of my Spanish tree very quickly, and then couldn't keep up with refreshing all the skills every day. So I'm slowly working my way through them to regild. Sometimes it takes me 2/3 goes to move up one bar, one or two of the skills it might take a little more. That's because I haven't learned the material, and amazingly the Duo algorithm can work that out.


    I have been re-gilding 2 or 3 skills at the time, that was fine. I am working hard to learn German, I am level 25 and I am doing reverse tree, I have books, I do Memrise etc. For me this is demotivating. I think it is just too boring to do 20 skills in one day, I have more German activities that will bring better results such as reading and trying to talk to people.


    If that is the case then it sounds like you don't need to use Duolingo for German anymore. At a certain point (tree finished, level 25) you have learned what you can from this site and you will get a better results with the other German activities you mentioned.


    I like to refresh the material so I do not forget it. My goal is to keep the tree gold for the rest of the year. But I agree with you I need something else in addition to this.

    [deactivated user]

      I was in shock when it happened to my German Tree. All the effort I put in making it gold disappeared.


      I just got my German tree gold (or the 2/3 I've done of it anyway) a few hours ago, and now I have 17 skills to strengthen. A perfect excuse to procrastinate!


      Once again, I don't seem to be on the A/B test. Which is okay, it means I have far less skills to strengthen right now.


      This is a great change.

      Although I suddenly have loads of skills to strengthen, and couldn't catch up with them all yesterday!


      And... has this change also affected my fluency rating? I've somehow jumped from 51% to 55% fluent in Spanish in one day.


      NO KIDDING! Same here. Losing gold on the tree raises my fluency level. Maybe if I lose ALL my tree levels, I'll be at 100% Fluency!!! WOO-HOO!!!


      Hahaha. Or, in Spanish, jajaja.


      unfourtunatley, u cant get 100% :(


      I give up I'd finally got to a reasonable state and ready to move on and then come to it again this morning and find myself back at the beginning of the refresh half of which I know I don't need because I completed only a few days ago.


      Is this why a few days ago, after finishing a new lesson I also got a popup saying "You strengthened skill X"? It only happened once so I thought it was a glitch.


      No, that does happen occasionally. It just means that the new lessons contained a word or two that happened to be in the old lesson as well, and so it got strengthened at the same time.


      Well that explains the desolation in my tree. On the other hand, I did think I was getting gold a bit too easily. Hopefully this will direct me back to weaker words faster!

      [deactivated user]

        I like this new feature I just have a question. If I make a mistake in my grammar does it know it was a grammar error or does it assume I don't know the word? For example if I use present tense but I should have used past tense. Or if I don't know the past tense of a word but I do know the present tense?


        Lower my gold standing on the tree, raise my fluency level. Makes sense to me!!!


        I wondered why a lot of my French skills that had been golden became all colourful again


        Hey, I just noticed that they've changed the voice on the skills. The voice is actually human, no more android-voice.


        I was very confused when my French tree started degrading so quickly! Thanks for the heads up! Time to sit down with a cup of coffee and get to it!


        This sounds like a great improvement, thanks a ton. Second all previous replies about making this post sticky, and even considering a notification. Fun fact is that I checked discussions before I went into my trees, and I was pretty scared after reading some posts, expecting a rainbow tree instead of golden. Turns out that my Italian tree stayed golden all the way, except for 1 skill: Basics 1. Well, I guess I can cope with that


        <entvoice>These trees were my friends! D: </entvoice>


        Arigatou, Hideki san, for keeping us well-informed! ^_^


        Awesome, this is definitely a great improvement. I sincerely hope that this A/B test will be conclusive =)


        Niiicee, impressing job, bless you all


        Thanks :-) I already wondered what had happened. I went from five golden trees to a single golden tree and more that 70 skills to refresh spread over the 4 other trees. Only my Spanish tree remained golden, but then again it is the oldest of all. It will take me a few days to get back to golden trees, but that is not a problem. In the end it is not about golden trees, but working with these languages on a daily basis.


        It seems to me, that I'm part of this Test for some weeks to month in the mobile App, and since a few days with the web-interface.

        What I experience, however, does not really fit to your intents as described: Now I only get the main words strengthed (about 5-7 each session), but all the other words in the lections around that words are completely ignored. To make it clearer: In former days, doing a lesson strenghed about 20-30 words, now it does so only on 5-7 words. This results into the tree degrading quickly and I'm being unable to keep it golden with approx 5 sessions a day---quite frustrating.


        A week ago i felt to be in the same situation as the one you now experience. During the days after my previous comment (see above) I have spent a lot of time on reguilding my trees. Since then, I don't have an issue keeping the trees golden. On average 2-3 skills need an update per day in each tree.


        I think the new strengthening algorithm is an utter DISASTER. The results seems to make little or no sense whatsoever. I can do a lesson today, and do quite well on it, yet be required to "strengthen" that skill four times in the next week. My daily goal is 20XP, which is an average sort of plan. I resolved that I would do the 20XP in new lessons (so that I am learning something new each day), and as extra practice above and beyond the 20XP, I would strengthen anything else that needed strengthening. That worked fine for a time until you screwed with the system. Now I have anywhere from 13 - 16 items appearing throughout the day that need strengthening. What began as "a few minutes every day" is now becoming a marathon, requiring a couple of hours or more every day. For me, that is simply not sustainable.

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