"Strengthen Skills" bug?

I love the idea of the "Strengthen Skills" feature, but it does not work well for me. If I use it, I end up practicing extremely elementary skills, which is not very useful, and it's not getting any harder.

For example, every day it asks me to translate "la niƱa". It definitely asked me to translate it both today and yesterday. However, if I look at the list of words in my vocabulary, it says I haven't practiced it in three days.

Perhaps there is a bug where practice isn't being properly accounted for?

June 3, 2017


Unfortunately, this isn't a bug; they added a new algorithm which decreases the strength of each category within 24 hours (mentioned here:, thus making the strengthen skill feature in the main page impractical for daily learning of advanced words since it only cycles through the most basic categories.

I have been experiencing this as well for almost 4 months now and even posted several topics and discussed with other posters with the same issue as this and yet no moderators are addressing this issue. The fact that they changed the frequency of devaluing of each categories makes it hard to keep up with the more recently learned words through the strengthen skills option. I am aware that there is a manual option in each category, but it is inefficient and time consuming.

If, say for example, a user has the whole tree completed and needs to review advanced words, he/she needs to choose the advanced categories manually, which will most likely make him/her miss out on other advanced words in other categories which he/she might not noticed or forgotten. The fail-safe way to counter this is doing the strengthen skills option in the main page to run down through every categories in his/her tree, but this way is very impractical since it will just waste precious time relearning well-known words which might make about half of the tree, and not to mention, this must be done everyday. If the users are paid per hour to do this, I would gladly do so, but it isn't.

I can't be having to waste almost half my day just going through all the learned categories everyday to ensure every word is still in my memory; the old algorithm serves this well already since it only cycles through your weakest categories and periodically adds other words to check if you still remembered it.

In my opinion, there's no need for change since the old algorithm delivers as is, in fact, the newer version of this algorithm just made it SHI-... *ahem* broken.

June 4, 2017

I noticed the exact same thing. I always use "Strengthen Skills" to practice but now it only repeats the same simple phrases (for example "nord" in Italian) and they doesn't seem to count as done, that's why they are repeated over and over. Also, my skill is not strengthening, unless I reach all 20 questions of the quiz. Otherwise I keep repeating the same phrases again and again. This feature is useless for me now and maybe I will stop using the app. I don't learn enough in the amount of time I spend.

June 5, 2017

Using this feature, it will begin with the first skills that have lost strength, which is why you'll end up reviewing easier skills. You can go to a specific skill to strengthen it to avoid reviewing more simple skills.

June 3, 2017

Thanks for the response. I understand the idea behind starting at the beginning, then progressing forward. But if every day I need to start back at the beginning, it is not a useful feature to me.

My theory is that there's a bug that's not properly counting the words I practiced the previous day, which is why my practice is so repetitive. I'm hoping the Duolingo team can look into this and implement a fix.

June 4, 2017

My thoughts are with you; the feature isn't useful at all. Another user mentioned before that the strength of a skill decreases within 24 hours, as stated in a discussion thread:

June 4, 2017

Moreover, if they are using this as a ply to gain more income for staying afloat (and I understand that they need to reach at least their break-even) which was implied here:, they must at least had have compromised with the users in which way is the best for both parties.

As I see it, Duolingo's staff's lack of communication between them and the users causes issues like this since they rarely post upcoming changes with user feedback in mind. If this continues, most likely that Duolingo will be shooting itself on the foot and in the long run, with the popularity of other language learning sites, they would likely fall behind other competitors.

June 5, 2017

As a follow up, here are screenshots demonstrating the issue:

June 6, 2017
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