Monday, September 29, 2014

Duolingo: Language Learning as a Game

What is Duolingo? (Updated December 30, 2014)

Duolingo is an award-winning free, web-based program for learning foreign languages. Duolingo manages to make language learning fun by turning it into a video game, but, more important, it also manages to be very effective. It presently offers English speakers a choice of five languages (plus four in beta and seven under development), and has lots of options for non-English speakers as well.

I have been using Duolingo since January 2014 (351 days as of December 30, 2014). I have completed the Spanish and Italian courses, I expect to finish the French one in April 2015, and I have just started the German one. I'm very impressed with Duolingo, and I strongly encourage anyone who wants to learn a language to give it a try. For a free service, the quality is astonishing.

And it's not just me. In a December 2014 article, PC Magazine said, "Duolingo is the best free online language-learning service." So it's worth taking a look at it.

In this posting, I'll describe the basics of how to use Duolingo, I'll talk a bit about how it works, and I'll finish up with suggestions on how to get the most out of it. I won't talk about the mobile version (even though I know it's very popular) simply because I haven't tried it myself. Nor will I talk about the "Immersion" feature, in which advanced students collaborate to translate documents.

How Do You Use Duolingo?

Skill Tree

Like any system for learning a language, Duolingo has a set of "skills" that you need to learn, divided between vocabulary (e.g. "Household," "Places," "Directions," etc.) and grammar (e.g. "Irregular Plurals," "Verbs: Past Imperfect," "Determiners," etc.) Unlike a textbook, which might have twenty chapters, Duolingo has a "tree" comprising 60 to 70 skills. Here's the top portion of my new German tree:

The gold skill, "Basics 1" is the only one I've completed so far (after three days). The two colorful ones under it represent skills that I'm allowed to attempt now. The gray ones below are skills I'm not allowed to try yet. When you complete the tree, you have "beaten the game." Note the similarity to a computer game where you complete quests that set you up to do more quests until you reach the final goal.

The upper right corner shows "experience points" (XP) which are earned by answering questions correctly. You earn XP by completing lessons, which advances you in the language (and opens more of the tree). XP lets you compare your progress with friends and family.

In the upper left corner, you can see that I'm currently at level 2 in German. Level is a function of the number of experience points (roughly the cube root, so each level requires more and more points). Again, note the similarity to a video game.

When you have finished all the skills, you have learned the language. If you did nothing but Duolingo, you would probably reach a CEFR level of A2. That's enough to "get by" if you travel somewhere. It's not enough to do much reading or hold serious conversations, but it'll sure impress your friends.

If you supplement Duolingo with other resources (as I'll describe later) you should easily reach B1 and possibly B2, at which point you can read newspapers and attempt novels. But even A2 is nothing to sneeze at. It sure is a lot more than you get out of most video games! It's quite a lot to get from a free one.

Lessons: Inside a skill

If you look closely at the tree above, you'll see that the "Basics 2" skill looks like a pie chart. That skill comprises five "lessons," and so far I have done two of them. If I click on Basics 2, I can see the whole list.

Each lesson is described in terms of which words it teaches. Lessons must be done in a particular order. If I click on "Lesson 3," it begins the quiz for that lesson.

Some lessons (especially the earlier ones) include grammar tips. It is almost always best to read these after attempting the lessons. Otherwise your eyes will glaze over--much as they might have in your high-school language classes. The best time to read a grammar rule is at the point where you're wondering "why do I have to say it like that?" Anyway, the tips are generally good--just don't think you have to read and understand them before doing a lesson.

Quizzes: How you complete lessons

Quizzes currently have seventeen questions, of which there are seven types:
  1. Foreign to English Translation. These show you a sentence in the language you are trying to learn and ask you to translate it into English.
  2. English to Foreign Translation. You see a sentence in English and must translate it into the foreign language.
  3. Listening. You hear a sentence in the foreign language and must type what you hear. (Not a translation.)
  4. Multiple choice. You are given a sentence in English and shown three sentences in the foreign language. You must pick the ones that correctly translate the English sentence. This works best if you try to do the translation before you look at the multiple choices.
  5. Match the picture. You are shown a word in English and three pictures, each labeled with a foreign word. You pick the picture that matches the word. Most (not all) new vocabulary is introduced this way.
  6. Translate one word. Sometimes it gives you a single word in English and asks you to type it in the target language.
  7. Speak into the microphone. This one is supposed to test your pronunciation by having you read something, but I was unable to make it work at all. Reports from those who've tried it suggest that at this writing the feature doesn't work all that well at the best of times, so I didn't try too hard to fix the microphone problems. Disabling the mic in the settings menu makes these questions go away, and I think that's what most people do.
Most of the question types give you lots of opportunities to hear the foreign language spoken. You can repeat what you hear, but other than the speak-into-the-microphone question type, there's no feedback from the program.

Obviously the translation exercises have the problem that there are often hundreds or thousands of ways to translate a given sentence. The Spanish ¿Es su libro? Could mean "Is it your book" or "Is it his book" or "Is it her book" for example. Duolingo generally has all the reasonable translations, and it benefits from a mechanism for users to report missing ones, so it gets better over time.

In the year I've been on Duolingo, I have seen them adopt at least 100 of my suggestions, so they do listen to their users.


Here's an example of a German-to-English translation question with a correct answer.

The red bar across the top shows how much of the lesson I've done. The word in gold, sind, is new vocabulary in this lesson. the number 2 on the right is the total number of questions I've answered so far--right or wrong. Whenever I get an answer wrong, the bar moves one to the left. That means each wrong answer cancels out one correct answer. You never "die" (like in many video games), but it can take a long time to win. The only way to lose is to click that Quit button in the upper right.

Other types of questions have slightly different formats, but the basic idea is the same: answer questions to complete lessons. Complete lessons to master skills. Master all the skills to learn the language. That's the whole thing in a nutshell.


If you look back at the skill tree, you'll see a long blue button on the right titled "Strengthen Skills." This creates a custom quiz based on the words or phrases you either seem to be having trouble with or which just haven't come up in a while. Doing review lessons doesn't advance you down the tree, but it does keep it from "weakening." If you don't do any review lessons, after a while the earlier skills will turn from gold back into some other color. They'll even have strength bars (like a wi-fi signal) that will gradually drop. It's Duolingo's way of saying that it thinks you haven't really learned this material. Weakened skills don't affect you finishing the tree, but most people want to keep their tree all gold. That's a good thing. I have written at length about the best strategy to keep a Duolingo tree gold.

The optimal mix seems to be to do two review lessons for every new lesson you attempt. You don't need to do a new lesson every day, but it's a good idea to do at least two review lessons each day. Three lessons a day takes about 30 minutes. (Longer if you do outside study.) If you can't commit 30 minutes a day to it, you probably shouldn't be trying to learn a new language in the first place.

If you really can do one new lesson every day, it takes about one year to finish a language. Since you'll have days when you don't want to do a new lesson, figure anywhere from 18 months to two years.

How does it work?

We don't need no grammar lessons

Despite the extensive grammar tips for the lesson above, Duolingo expects you to learn the language by trial and error--not by learning rules.

In a Redit Discussion in 2014, Luis Ahn, the founder of Duolingo said, "I, personally, don't like vocabulary, grammar or verb conjugation. My dream in life is to be able to teach you a language without you needing to read textbooks about indirect objects. In fact, I consider the use of grammar to be discriminatory against those who unfortunately didn't have a very good education in their own native language (which is the majority of the world's population). I think slapping 30 pages of grammar before every lesson is the easy way out -- instead we should strive for something that everybody can consume."

The person who approaches Duolingo purely as a video game will miss questions over and over until he/she has memorized the words and phrases needed to finish each lesson. Keeping the tree gold requires remembering all those words and phrases. The whole concept is that the brain will deduce the patterns so it can reduce the memorization effort and that after a while, correct expressions will start to "just feel right." To some degree, this really does happen.

The makers of Rosetta Stone have a similar philosophy: they too believe that through repeated exposure to sentences in the foreign language, your brain will naturally deduce the grammar rules, and you'll speak the language without ever having studied the grammar at all. After all, children learn their native languages without studying grammar at all.

Or do we?

Things aren't really this simple. Linguists don't believe that adults can learn languages the way children do, so one would expect a few problems. And there are.

Almost no one ever actually finishes Rosetta Stone. A University of Maryland Study showed that out of 150 people who had free access to it, all but one gave up during a twenty-week period. One wonders how they stay in business. My personal suspicion is that most people who paid $500 for the product a) blame themselves for not working hard enough and b) convince themselves that they're not really quitting--they're just putting it aside until "later."

Duolingo doesn't publish statistics, but it's clear from the discussion forums that only a fraction of those who start it ever finish their trees. City University of New York did a study that asked 88 people to use Duolingo for 30 hours over an eight-week period, or about half an hour per day.  One quarter of the people managed to do this. That sounds better than the Rosetta Stone numbers, but we don't know what the 20-week results would be like--never mind the 65-weeks it would take to finish the tree.

So it's not actually clear that Duolingo has a better success rate than Rosetta Stone, but it does have one very big advantage (other than being free): it has a strong online community.

Discussion as Study Group

If you look back at the last picture (of the failed French translation question), down at the bottom there's a button labeled "discuss sentence." If you click on that, it takes you to a forum where the users discuss the challenges of this specific sentence. These discussions are almost entirely about grammar.

Studying a language with Duolingo is like taking a college class from a professor who never bothers to show up to class, but somehow the TAs are regularly giving quizzes anyway, and they're harsh graders who can't be argued with. The discussion sessions are a study group where you and other students get together to try to teach yourselves the subject. Different people attempt to explain the rules, offering links to free outside material. Native speakers pop in to offer advice. And somehow it works. For those who stick with it, anyway.

Duolingo does listen. A year ago almost none of the lessons had any grammar tips whatsoever. In response to endless user complaints, they have gradually been adding more and more tips in more and more languages--and from what I can tell, those are largely based on the sort of questions users ask in the forums.

Supplemental Materials

I said above that if you do nothing but Duolingo, you'll reach A2 competence in the language in a bit over a year. But what if you want more?

Grammar Books

As with a video game, Duolingo has the equivalent of walk-throughs and game guides. These correspond to free online grammar sites and professionally-produced thousand-page grammar texts, respectively. For example, the French Grammar site is extremely popular with Duolingo users. For the first few skill levels, that may be all you want, but as you move through the language you're likely to want something more solid eventually.

For French, I bought Schaum's Outline of French Grammar: Sixth Edition, and it's quite good. Serious students will want a "Reference Grammar," which is more like an encyclopedia of the language and dives deep into difficult areas. I use Advanced French Grammar (L'Huillier, 1999), but most language students probably won't want anything that heavy-duty.

Either way, whenever you see something you don't understand, you thumb through the grammar book until you've figured it out. This is something you'd probably spend thirty minutes on once or twice a week.


For French, Spanish, and Italian, nothing beats WordReference. This free online dictionary gives you definitions, pronunciations, conjugations for words and phrases, and it automatically searches forums that have ten years worth of answers to questions about the meanings of words.

Flash Cards

Duolingo does a great job of drilling you on grammar (even though it purports not to teach grammar), but it's a little weak on vocabulary drill. If you supplement it with a few minutes a day of flashcard drill, it will make a big difference.

Duolingo has a very simple built-in flashcard program, but it drills word forms (e.g. mangeais "I was eating") as opposed to headwords (e.g. manger "to eat") and it only drills from the language you're learning to English--not the other way around. There are no "glosses"(hints that let you distinguish otherwise-equivalent words) so, for example, when it prompts with tiens you don't know if it means "I keep" or "hey there". Finally, it doesn't drill phrases, which doesn't help if you want to learn that it's commencer à not de. Duolingo's flashcard program is very new (as of this writing), so it will probably get better over time.

Instead, I use the Anki flashcard program, which is a free download. I create the cards myself based on what I get wrong or need to look up on Duolingo each day. Then I do a daily drill of up to 100 words per language (bidirectionally, so, for example, when I drill French, I see a mix of English-French and French-English cards), which takes from ten to fifteen minutes. I have a posting about using Anki flashcards for vocabulary drill.

The Duolingo Wiki

Finally, serious, long-time Duolingo users have created a Wiki for Duolingo which gives countless tips on how to make the best use of the software. Again, any serious videogame has a fan-maintained Wiki that gives you all the details; if you use Duolingo, you should bookmark the Wiki.

Speaking and Writing

Duolingo doesn't do a lot to directly develop your skills at conversation or composition, but it definitely puts you in a good position to do this yourself. I use the Lang-8 site to practice writing, and I have used Meetup to find local conversation groups for Spanish, Italian, and French. These are things that make more sense to try when you are almost finished with your Duolingo tree.


I have written at length about the importance of reading novels to help learn foreign languages. I still think this is the best way to advance, once you have reached an intermediate level. When you have learned the past tense in a language, I think it's time to start trying to read newspapers. Most of the worlds major foreign-language newspapers make at least some articles available for free. For French, I was delighted to learn that Le Monde has lots of free online content. Try to read just a paragraph or two a day to exercise what you learned from Duolingo. Use Wordreference for anything you couldn't figure out.

Once you get to the point where you can read entire newspaper articles, try books. I have some suggestions for how to pick a foreign novel to read. If you do this, you'll be pleasantly surprised to discover that Duolingo has done a good job of selecting vocabulary; especially if you like action-adventure and/or crime novels.

Alternatively, use Duolingo's own "Immersion" feature, which lets you practice translation in a collaborative environment with other learners. (Think of it as the co-op version of the game.)

Whichever route you take, read. As soon as you are able to do it, read. Unlike speaking or writing, you can do it every single day, and it has the potential to lift your abilities in all the other skills simply because it boosts your vocabulary so much.


Duolingo is a remarkably effective free service for learning a foreign language. By making it into a game, the Duolingo people have managed to make learning fun. This may be the most effective way ever designed to learn a foreign language, short of studying abroad.


Unknown said...

Excellent summary Greg. I love Duolingo!

Vee (Scratch) said...

Interesting Duolingo review. Luis Ahn's views on grammar is revealing, I think many DuoLingo's users should take note.

I have one small objection. DuoLingo is great for reading and writing, but you're being limited to finite text and one voice for listening. I'm not sure if Duolingo alone will be enough for CERF A2? Duolingo doesn't offer a variety of voices to hear. Duolingo does not provide a platform to practice speaking. I may be wrong but I'm not so sure about that claim. I think that you should obtain other resources, it may be necessary.

Greg Hullender said...

You're definitely correct that Duolingo doesn't prepare you for speaking, although it does push you to figure out how to express yourself.

Anecdotally, I've been told that Duolingo people do okay in the speaking portion of the CEFR simply because they're not afraid to speak. One of the hallmarks of the A1 student is that he/she is terrified of speaking. The comment I remember (partly in jest) was that willingness to speak bad Spanish was enough by itself to secure an A2 on the speaking portion.

Where Duolingo folks do have problems is with a handful of tasks like "address an envelope" that are expected of anyone doing any of the CEFR exams at those levels. They're easy to learn, but not part of Duolingo's curriculum.

I've seen no serious study of how Duolingo students do on CEFR exams. Anyone planning to take one should prepare for it by looking at the sample exams, if nothing else.

Anonymous said...

I liked your review, Greg. I LOVE the Mar Plateado idea! I have been searching for something like this for a while. I also am more interested in translating whole articles myself, rather than bits and pieces. I have sent a join request. I am ayePete on Duolingo.

PS: I am also a programmer, and I would REALLY appreciate it if you would check out my blog postings and give your criticisms. Thanks in advance!

Unknown said...

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Jim said...

You make a very persuasive case for Duolingo and I shall certainly now have a look at it. However, for anyone like me, not keen on staring at an LCD screen but very keen on grammar, the “Living” Series (Living Italian, etc) of grammar-based language course books is reliable and affordable. In addition, April Wilson’s German Quickly is outstanding and Franco & Sandberg’s Spanish for Reading great fun.

Dover offers a very good series of “Dual Language” books with en face translation that can aid the transition from learning a languge to reading it.

Harald H said...

About the microphone feature: It certainly does not work well - i've tried to speak total gibberish, made conscious errors etc and it often lets me through anyway. To say nothing about the times I do not succeed in pronouncing the sentences in the Swedish course even though I am a native Swedish speaker. BUT I keep the microphone feature on anyway, and for one good reason. Once I've said the phrase, I can listen to my recording, and then the Duolingo voice, and compare them to hear what I'm doing wrong, what makes me sound un-Italian or un-French. So there is a reason not to switch it of.

Anonymous said...

I love Duolingo and it's amazing that it is free, but I think you can't really get too far in any language with it. Duolingo in my view is best as a supplement to a formal course or in conjunction with other teaching methods. As a supplement, it is fantastic and wonderful and I salute everyone at Duolingo for the incredible job they have done.

Carl Kruse

smb.yoshi said...

Thanks for the detailed review, it was very informative.

I was wondering if it would be a good idea to learn strictly from Duolingo first, get to about A2 level, then branch off to the 'supplement materials' (the ones you have posted). Or should I read several articles a day from and other sites, while working on Duolingo?

Greg Hullender said...

I think it makes more sense to supplement Duolingo starting from the very first lesson. It's a great way to organize your language learning experience, but I don't think it's really enough by itself.

Anonymous said...

Greg, again thanks for the insights. I am studying Italian. I just returned from 3 weeks in Italy. Though I am not ready to carry on more than minimal conversation, I was able to use my Italian to improve both understanding Italian speakers and expressing myself to Italian speakers. Excited to have accomplished so much in 10 months, disappointed that I had not progressed further. I like the suggestion to pick up a grammar book. I ran across the Italian Grammar for Dummies book and even though I haven't finished it the book has explained things that DL doesn't. I plan to continue to work on my Italian. Once both trees are gold German is next. Autodidactyl (my duo personality).

MindTheGap76 said...

For folks looking for an automated flashcard solution, I've found is an excellent supplement to Duolingo. It is absolutely free, uses a similar game-ification approach as Duolingo, and solves the flashcard problems Greg describes above. Like Duolingo, it tracks which vocabulary you've had trouble with or not revisited recently and focuses on those areas.

Memrise works by signing up for various card-packs. There are a large number of language packs you can pick, but there's almost always an option for a Duolingo-specific pack that matches the vocabulary of the Duolingo lessons.