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Strength Bar Lessons

Our goal is to find the best way to teach languages. One of the key initiatives we're working on is to make our lessons adapt to you. Already, the Duolingo practice sessions use everything we know about your language abilities -- what concepts you know, how well you know them, etc. -- to generate exercises that help you refresh what you've learned so far. Going forward, we want to make the lessons themselves more adaptive to each user: from choosing examples that introduce new words while letting you practice old concepts you haven't mastered, to rearranging the tree to suit your learning goals.

As a first step toward this vision, we've been testing out a new game mechanic for lessons, and today we're starting to test it with 50% of our entire user base. In this new format, the goal of a lesson is to fill up a strength bar. When you answer exercises correctly, the strength goes up, and when you get them wrong, the strength goes down. There are no more hearts, and there is no need to redo entire lessons when you've lost all your hearts. Instead, if you are comfortable with the material in a lesson, you'll be able to breeze through it, and when you don't know it as well, you'll have to do more exercises until you master the concepts in the lesson.

As part of this test, we're trying out two visual designs for the strength bar. One is a simple green bar similar to the one used in the placement test:

The other is a larger, centered bar that includes the skill icon:

So far, the test shows that new users are more engaged with this format, so we're hopeful it will also be a success with existing users. If it does succeed, this new lesson format will pave the way for a more adaptive Duolingo experience, so I'm very excited.

As usual, we'd love to hear what you think!

P.S. Since this experiment replaces the heart system, we've automatically refunded anybody who purchased a heart refill through the store. : )

December 3, 2014



I think that's a great idea, Luis!

Being able to continue practicing the same material until you actually reach the right amount of strength seems less disruptive than having to restart the lesson each time you lose three hearts. I'm no expert in language acquisition or learning, but it seems that repeating concepts as often as necessary, for a significant amount of time, within one exercise, may be a great idea for really getting those words and concepts down. That seems to work for me, anyways. :)


Same here Lavinae. This sounds like heaven has finally answered our prayers. Everyone in Group A needs to ramp up their learning so this thing can beat the A/B test. I want it, please. ;)


so, no more lingots from a perfect lesson? that's a bit dissapointing.... (yes, i know that they are useless, but i like collecting them)


Same here, but if you complete a whole skill, you'll still receive your two lingots. Not receiving one lingot is a disappointment for me as well.


You are right. And I like the Lingots for the bonus functions


And no more bonus XP either, leveling up will now take up to 30% longer...


I have the new system with the old type bar. Less frustrating yes, but Im not sure the motivation is quite the same. I hated losing a heart and it made me less slapdash. It was an incentive to finish with full hearts. Now i will finish eventually and feel a bit cheated to finish with no error and no corresponding pat on the back. Is it possible to get an extra couple of points or a lingot for a perfect lesson? It doesnt matter that it is a worthless currency, for me the reward system works. I have to say I have really really enjoyed Duo Lingo (been obsessive even!) and I have tried at least a dozen, if not more, other courses many thanks :)


For new lessons, I prefer the old system (hearts). To refresh lesson (without timer) I'd choose the new one.


I'd like to see this version A/B tested!


My thoughts exactly.


New lessons is the time when I HATE the hearts system, not when I like it (which is never)! Imagine starting a new skill, then getting 5 questions wrong because you're just starting the skill when you're only a few questions away from the end of the lesson! This new system seems like it would fix everything about that, so they should definitely introduce it because it would be a HUGE improvement. I can't even comprehend how ANYONE can like the hearts system.


Part of the test group! (Centered bar) During the heart system, I was always checking words even if i knew them - which was actually hurting my long-term memory. I've noticed that for something to stick in your mind, you need that active recall process happeneing (i.e. you won't memorize by reading something 15 times, but by reading it, trying to recall, reading it again, trying to recall more, etc. - at least for me). So for me, this system works better and I don't feel so paranoid about making mistakes.

In contrast, as for the centered bar, I guess they're still working out knicks, because my icon always shows the broken-egg rather than the actual skill's icon, although the color is matching fine. The number shown next to the egg confused me though. I think I would prefer it without a number there. Or maybe just a countdown to the number of correct responses? The current way it just counts up total responses (wrong or right).


Right! Exactly! I, too, would always check and thought about the same thing -- it was hurting my ability to recall! This new way I can already tell that I'm not checking as much and I'm more likely to try to recall it! And recall is just like a muscle -- you've got to use it or you'll lose it!


A number is totally fine with me. It's a good question whether they should rather implement a countdown, though, because if you have five wrong sentences, you'll need to translate 27 sentences in total and that is quite a lot if you ask me. Thus, a countdown might be a great idea, but I obviously don't know what other people will think concerning this question.


This evening I found I'm in the test group, simple green bar subgroup.

After some lessons and practice, I'm a fan. Going back to the Android app and its hearts is going to be a real wrench. The new system fixes my main problem with DL. I'm not much motivated by lingots - buying hearts seems like cheating - so crashing out of sessions, especially near the end, double specially when down to a careless mistype, or (worse) phone keyboard autocorrection or DL rejecting UK English, was punishment without significant reward.

The upshot was DL was starting to remind me of my school French experience (1974 O level, for UK old-timers). For a flavour of this, check out the scene in Life of Brian where Brian has his Latin corrected at gladius point by John Cleese's centurion. I had many Latin lessons just like that - minus the cutlery, just with the same threat level.

With DL starting to feel like the punishment/reward system was all downside, the most important thing was At All Costs Don't Make A Mistake. Don't use your memory, but check the word translations, and as much else as you can. I've never managed to learn any language to a useful degree, and know that especially with French I am terrified, incoherent and tongue-tied when actually in France, because I'm sure I will make a mistake. I suspect that, in reality, if you want to learn to speak a language, you have to take the plunge, try, and make a bucketload of mistakes all over the place. With the new system I am far more relaxed about making mistakes, because they're not going to chuck me back the beginning of a lesson, and so I'm not checking nearly as much.

TL;DR: Bravo! Thanks for the change.


Thanks for your great story!


That French teacher must be a great traveler because I had her in HS in NY. The last language I'll try on Duo will be French. I'll finish hoch Klingon and still not go near French. I loved your so wise statement re no longer using other aids to do the sentences. Guessing is a highly prized skill in language learning and now we can "afford to go out on a limb."

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