Tuesday, December 30, 2014

How to Make a Gold Duolingo Tree

Finishing Duolingo isn't enough; you want all the skills to be "gold," and you want them to stay gold. In this post, I'll talk about how to "regild" a completed tree, what to do about weak skills if you're half-way through a tree, and how to keep a tree gold from the very start. I'll also discuss how to do this in a way that actually teaches you something--it shouldn't be an exercise in aesthetics!

Those who are impatient can just skip straight to the end and read what I recommend as the best practice. For everyone else, I'll explain what it is we're talking about and how I reached the conclusions I did.

The Decaying Tree

When you first finish a skill, Duolingo turns its icon gold, and five "strength bars" (like on your phone) appear beside it. If you don't do regular "strengthening" exercises, though, the strength bars will gradually weaken from five to one, and at anything less than five, the skill appears in its original color--not gold. This is what we mean by "strong skills" and "weak skills." "Regilding the tree" means doing enough exercises to turn the whole tree gold again.

People who do new lessons but never do review lessons get used to the way a wave of color chases them down their tree. Those who took the placement test and skipped over a large part of the tree are often stunned when a huge slab abruptly turns color all at once. In both cases, Duolingo is sending a message that those are skills that ought to be reviewed. This post is for those who want to do something about weak skills and who want to enhance their language learning at the same time.

Why Bother?

As Duolingo warns, if you don't review what you learned, you'll start to forget it. Lots of people eventually abandon Duolingo because they get about a third of the way down the tree and then they have terrible trouble finishing new lessons, due to the fact that they've forgotten too much of the earlier material. Doing regular review lessons spares you from this.

Duolingo has a decent algorithm that tries to target the things you most need to review. Done right, the review lessons really shouldn't end up being a waste of time--they should help you solidify your understanding of the language. And they often contain material you didn't see when you did the skill for the first time.

Two Kind of Strengthening Exercises

To reverse this decay process, you can either do a skill-specific strengthening exercise or a general strengthening exercise. To do a skill-specific one, you pick a weakened skill and click on its icon. On the right, you'll see a colored box showing the strength of the skill, and inside that box is a button to strengthen the skill. Press that button and Duolingo gives you a review lesson targeting the skill as a whole. That is, it doesn't just repeat one of the lessons--it asks you questions drawn from all of them.

Because it only takes 17 correct answers to complete a lesson, and because Duolingo usually has far more than 17 possible questions per lesson, when you do a review lesson you will frequently see sentences you never saw when you did the skill in the first place. Usually not entirely new words, but you'll definitely see new ways to use the old words.

Depending on how weak the skill is and how big it is (i.e. how many words it covers), a single strengthening exercise may not be enough to make it gold again. Repetition may be necessary. On the other hand, occasionally you'll strengthen some entirely different skill that just happens to share a few words with the one you were trying to strengthen.

To do a general strengthening exercise, you go back to the main menu and click the blue "Strengthen Skills" button on the far right of the screen." This brings up a review lesson that has a random mix of things you have already studied but that Duolingo thinks are weakest.

Because the benefits of the general exercise are spread across the entire tree, it usually strengthens anywhere from zero to three skills--some people have reported as many as 13.

In short, your tree weakens over time, and you have to do strengthening exercises if you want it to stay (or become) gold. The question is how often to do them and what kind to do. To answer that, we'll start with a look at Duolingo's algorithm--what's known of it, anyway.

How it Works

Duolingo does not publish much about the algorithms they use for weakening and strengthening, but they did make at least one posting with hints about it. Further, a Duolingo user with the handle pinkodoug has made an extensive study of the Duolingo JavaScript and he has some plausible ideas about their algorithms for strengthening and weakening.

Drawing from those sources plus my own experiments, here's my best guess as to what they do. (N.B. these are my conclusions, so if they're wrong blame me--not the sources above.)

To Duolingo, strength is about words, not skills. Strong words have a score of 100%, and they decay over time until they reach zero. All words are decaying all the time, but some words decay faster than others.

You can actually see this if you click on the "Words" tab at the top of the home screen.

This shows all the words that Duolingo thinks you've studied so far. It tells you how long ago you practiced each one, and it gives each word's current strength using a bar system that goes from 1-4 (not 1-5 the way skills do). If you sort by "Last Practiced," you'll see that the older words tend to be weak while the latest words are almost all 4-bars strong. This is because all words weaken over time, but, as I said before, some words decay faster than others. We'll get back to this last point in a minute.

Every skill is associated with a set of words--probably the same words that you see in the individual lesson descriptions. Whenever those words have an average strength of 2.5 bars or more, the skill is gold. Otherwise, it shows the original color, and the skill-strength declines based on some function of the average word strength.

Whenever you do a review lesson, it targets some number of your weakest words for review. A skill-specific review only picks words from that one skill. A general review picks words from every lesson you've completed so far. Otherwise they're the same--with one important exception: in the tips that Duolingo offered, they said that skill-specific strengthening turns your tree gold faster than general strengthening does.

As long as you complete the review lesson, the targeted words all get set back to four bars whether you get them right or not. The catch is that getting them right makes them decay slower in the future. Getting them wrong or using the hints makes them decay faster. This is why some people report making tremendous efforts to strengthen every single skill only to watch them start decaying again a few days later.

The fact that some people seem to keep their trees gold without much effort suggests that there actually is an optimal way to do this. To determine what that might be, I did a few experiments--with help from a friend.


Greg's French Tree

For the past twelve months, I have been slowly going through Duolingo's French tree, following a rule of doing two review lessons per day followed by one new lesson. In that time, I have completed most of the tree, and it has never weakened. That is, although an individual skill has weakened two or three times, I simply strengthened it specifically and thus ended the day with a solid-gold tree. During that time, I had three different week-long vacations during which I couldn't do lessons. Even so, when I got back, the tree was still gold. Others have reported similar experiences.

This suggested to me that it is possible to have a durable gold tree without a whole lot of work. That is, it seemed that as few at two general strengthening exercises per day might be enough, if done daily for a long enough time.

Naomi's Italian Trees

My friend Naomi in New Zealand was interested in exploring this, and she agreed to help do a few experiments. She had finished her English-to-Italian tree (aka the "forward tree") in just a few months and wanted to gild it. She had also just completed the Italian-to-English tree (aka the "reverse tree") in a single day and wanted to keep it gold.

The experiment was very simple: On her forward tree, she did two general strengthens per day. On the reverse tree, she did three general strengthens per day. Back when Duolingo allowed you to fail, she would persist until she completed that number, although, as it happens, she rarely failed an exercise.

Here's what happened.

With three general strengthens per day, the reverse tree got worse for about 40 days, leveled off for about a month, and then started improving in an irregular sort of way.

The forward tree decayed steadily, reaching 57 weak skills on day 91. At that point, we changed our strategy.

Starting on day 92, Naomi began doing three skill-specific exercises instead of two or three general ones. She selected the skills to strengthen by picking the weak skills highest in her tree. She applied the same algorithm to both trees.

We only have 13 days of data with the new method, but the results speak for themselves.

This graph shows how many weak skills were left each day after Naomi did her strengthening exercises. This shows that the reverse tree was 100% regilded on day 99 and that it has remained so for six days now. On the present trend, the forward tree will be regilded in two more weeks.

Obviously this strongly suggests doing the per-skill exercises rather than the general ones--just as Duolingo had advised people. In fact, the per-skill exercises appear to be more than three-times as effective at regilding. It also suggests that two exercises per day was not enough.

We adopted one additional rule: substitute general exercises for specific ones if there are no weak skills left, but never do more than two general exercises on the same day. That is, if the tree has any weak skills, then Naomi still does three strengthening exercises--padding them out with general ones as needed, but if the tree was solid gold to begin with, then she only does two generals, not three. The idea is that, like with my French tree, a durable gold tree should eventually need only two per day to maintain it.

Note: Throughout the process, Naomi reported that the algorithm seemed to have a knack for finding exactly the things she was weakest on. She felt the exercise improved her Italian enormously, even if she did spend 91 days making no visible progress on regilding her trees.

Greg's Spanish and Italian Trees

During this time, I let my own Spanish and Italian trees decay. (Both had been gold on day zero of Naomi's experiment.) Over the next month or two I'll try to reproduce the results from Naomi's trees, but I wanted to share one key result that I got on the first day:

For the best learning experience, you should strengthen from bottom-up instead of top-down.

The reason to prefer bottom up is that it drills you in the skills you most-recently learned--the skills you are most likely to need help in. You'll discover that Duolingo has a lot more material for those skills that you never saw when you did them the first time. Most people have a weak grip on the last skills in a tree, so it makes a great deal of sense to prioritize strengthening them first. In contrast, the stuff at the top of the tree is far easier to do, but it's also far less valuable to review.

The exception would be for someone trying to resurrect a long-unused tree or for someone who has become overwhelmed and is considering quitting. Those folks should strengthen from the top down because it's equivalent to starting over, in a way, without losing everything you learned the first time. (In my view, no one should ever delete their Duolingo tree and start over.)

Other Issues

I always advise people to avoid timed practices and not to use the mouse-over hints unless absolutely necessary. I'll explain my reasoning for both suggestions.

Timed Practices

You buy the ability to do timed practices at the lingot store. It's a one-time purchase, but it's still a bad deal. The way it works is that when do a review Duolingo offers you the option to do timed practice instead of the normal kind. In fact, it becomes the default.

In timed practice, you only have a few seconds before the clock runs out and you lose the round. Every correct answer puts more time on the clock, so you need to go like lightening to keep ahead. In theory, this helps you develop the skills to handle conversation in real time.

Many of the people I've talked to who reported doing lots and lots of review lessons with little progress on regilding their trees told me they were doing timed practices. I think this strengthens the tree slowly because time pressure encourages people to skip long sentences. The earlier post from Duolingo said that every word counts, so it would make sense that skipping the long sentences would really hurt you.

Given that Duolingo's new UI is much more forgiving of mistakes, it probably makes more sense to try to get the same effect by simply going through the exercises as fast as you can, accepting the fact that you'll make more errors. As a bonus, when you do make an error, you can stop and study what you did wrong. Anyway, if you want to regild your tree, you should probably stay away from timed practice.


The other thing that seems to be strongly associated with lack of success is using hints. Using a hint means doing a lesson and mousing over a word to get Duolingo to show you the definition.

Unfortunately Duolingo takes this as a hint that you don't know that word at all, and it makes that word decay faster. Do use the hints if you really don't know the word. (We want to help Duolingo figure out what you really need to study, after all.) But don't use them just because you want to be 100% sure of a word before you press return.


Plan to do three exercises per day. If you can't invest that much effort, you probably can't do this in a reasonable time. With that, here is the system I recommend for making durable gold trees with Duolingo:
  • Always do a skill-specific strengthening exercise if there are any weak skills in your tree at all. Only do a general strengthening exercise if there are no more weak skills to do.
  • If there are multiple weak skills to choose from, always pick the one that is furthest down the tree. (That is, prefer skills you learned later over ones you learned earlier.) But, if you are effectively starting over (e.g. after a long absence or because you're overwhelmed) then pick the highest (that is easiest) weak skills first.
  • For an incomplete tree, do two strengthening exercises and then do one new exercise every day. If you're not ready for a new exercise, do a third strengthening exercise instead.
  • For a complete tree that isn't all gold, do three strengthening exercises every day, using general strengthening exercises if you run out of skill-specific ones.
  • For a complete, solid-gold tree, only do two strengthening exercises per day--both of which have to be general ones, of course.
Never do a timed practice. Never use hints.

Finally, take your time. Don't try to regild your tree in a day or two of inhumanly focused effort--followed by a month of neglect. A steady effort over a long period of time is the best way to do this. You'll learn the most that way, and it won't burn you out.

If you follow this plan, assuming that you are doing your best on the exercises, your tree will eventually be "durable gold," meaning it will stay gold with minimal effort on your part, even if you go on vacation for a week or so. How long it will take to get there depends on a lot of things, but a month or two seems typical. (It depends on how well you do the exercises and on how deeply decayed your tree was in the first place.) Have at it, and best of luck!

I would love to hear from anyone who gives this a try. Leave a comment and let me know how it went.

Sunday, December 14, 2014

Como Agua Para Chocolate

I finished Como Agua Para Chocolate ("Like Water for Chocolate") this week, and enjoyed it a lot. Other than requiring the reader to master a hundred or so words of cooking vocabulary, it should be well-suited to an intermediate reader with a good sense of humor. Young female readers may especially enjoy it, but it's really a fun read for anyone.

Outline of the story (no spoilers)

A basic but boring description

Tita la Garza is the youngest daughter of a wealthy Mexican family whose ranch lies in northern Mexico not far from the US border. The novel takes place during the Mexican Revolution in the early 1900s. Tita wants to marry Pedro Muzquiz, the boy next door, but her family's tradition says that the youngest daughter must stay home to take care of her mother. She rebels, but her mother is a very strong woman who brooks no disagreement. Tita boils with repressed anger and passion--like the water one boils to make hot chocolate.

A more exciting description

Strange things happen around Tita. Magical things. Surreal things. Forced to work in the kitchen, she pours herself into the work (and excels at it), but when she's very emotional--for better or worse--all kinds of things happen to people who eat her cooking. Even without Tita's help, the la Garza ranch is a place where people do strange things for stranger reasons, but Tita definitely pushes it over the top.

Strange things happen to the reader too. You laugh. You get angry. You get sad. And then you laugh some more. 

There are twelve chapters, named for each of the months of the year, although the story encompasses more time than that. Each chapter is organized around a particular Mexican dish that Tita will prepare, and you can bank on the fact that something unexpected will happen when people sit down at the table with it. 

The target audience

Unquestionably, this is a girl's book. The heroine is a teenage girl, all the strong characters in the book are women, and cooking is a major part of the story. That said, you don't have to be a girl to enjoy it, and there is a lot here to enjoy. For me, at least, the book flew by. I don't think I was ever bored.

Challenges Reading the Novel in Spanish


Como agua para chocolate has quite a lot of cooking vocabulary. You'll find the names of cooking utensils, actions for preparing and cooking food, and a long list of foods. Assuming you are reading on a Kindle, you'll find that the free monolingual dictionary almost always has definitions for these words, so be sure to check it whenever your bilingual dictionary lets you down.

A trick that is sometimes useful, especially for long lists of unknown words, is to use the translate feature on the Kindle. Although the translation often makes a hash out of complex sentences, when you have a simple list of nouns, it usually does a pretty good job, and it's far faster than looking up seven or eight words in a row.

There are a few references to the Mexican revolution that might throw you. One important one is that a follower of Pancho Villa is a *villista*, but none of my dictionaries told me that--I just had to figure it out.


For this novel, I tried an experiment: during the first chapter, I highlighted every word that I had to look up in the dictionary. I sometimes look up words even though I think I know them, so I didn't highlight anything if the result was what I expected. Just the words I really needed to understand the sentence.

At the end of the first chapter, I created a new deck of flashcards with Anki but instead of using my special template, I used the basic Anki template--the one that assumes you only drill in one direction and that you don't type the answers. On the front sides, I put the Spanish words I had looked up, and on the reverse I put the definitions.

Drilling on those words was really fast. For example, Anki might prompt me with:

I might think "that that means "to shell," and I'd press the space bar. Anki would show me the answer:

In this case, I'd be right, so I'd press space again to mark it correct and advance to the next card. If I was wrong, I'd press the "1" key, marking the card wrong for further review.

Although not as comprehensive as the sort of two-sided cards I create for serious vocabulary review, I could blitz through these one-sided cards like lightening, largely because I didn't have to type anything.

After drilling on the words from the first chapter, I proceeded to read the second chapter. Sure enough, lots of those words occurred again--even unusual ones. I repeated the experiment in chapters two and three. This fairly simple exercise made the rest of the book a good bit easier to read. I'll try this again with the next couple of books to see if I really think it's worth the trouble.

Amazon actually has a built-in flashcard feature called "Vocabulary Builder" which does almost the same thing. Unfortunately, as of this writing, there is a bug in the Vocabulary Builder that causes your Kindle to slow down and eventually lock up if you look up too many words with it. I can't get past a single chapter without having to turn it off.

Friday, December 05, 2014

Finding Foreign Novels to Read

One of the challenges of reading in a foreign language is finding novels to read in the first place. You want something hard enough to challenge you but not so difficult that you give up in despair. If you already have recommendations from friends or teachers, that may be all you need, but recommendations can go badly wrong too. (See the last section of this post for a story about that.)

Even if you follow my advice on reading a foreign novel with a Kindle, you are likely to spend a hundred hours or more on this book, especially if it is your first in the language. It's worth your while to take a couple of hours to pick one out.


Because my strategy calls for using a Kindle, it does limit you to books you can buy on a Kindle. This turns out to be a limitation, but not a fatal one.

Amazon has a large selection of foreign-language novels in the Kindle store, but you'll be disappointed to learn that it's only a fraction of what's sold in those markets. For example, I checked just now and there are 113,182 Spanish Kindle books in the US Kindle store, but on Amazon.es, there are 3,198,321 available. That calls for an explanation.

Unless you have a mailing address in the EU, Amazon cannot legally sell those books to you. This is because standard contracts with publishers set out different rules for different countries and those contracts usually only give Amazon the right to sell a book in a few markets. It's okay (in theory) to order copies of the physical, printed books, if you're willing to pay the shipping costs from Europe, but you cannot buy the e-books. The fault for this lies entirely with the publishers, who generally won't sign international contracts even for e-books. People complain about this a lot.

As a practical matter, there are plenty of interesting books in the US store; you really aren't going to run out. But sometimes I'll see a book review that praises the English translation of a foreign novel, and I'll want to see if I can read it in the original language. So far, I have never been able to.

The most you can do is write a letter to the publisher. Short of that, you can find the US Amazon page for the printed book and click the link that says "I want this book on the Kindle." 

The upshot is that you have to start your search with the set of books that are actually for sale on Amazon in the US.

Selection Criteria

As mentioned above, you want to pick a novel that'll be fun and challenging but not too difficult for you. Toward that end, I've come up with a set of rules. They aren't hard-and-fast rules, but they're a reasonable guide to start with. As you read more and more books, you can relax some of these rules.

The most important thing--above all else--is that you pick a book that interests you enough to stick with it. This is a principle that supersedes any rules.
  1. The book must be an "authentic novel." This means written by and for adult native speakers. That rules out translations, children's books, and materials for students. The reason is that these things all dumb-down the vocabulary and sometimes use unnatural grammar.
  2. The book must be new to you. If you already read an English translation of the book, don't try reading it again. It's not just that this makes it too easy--it also makes it too boring. Worse, because you already know what you're reading, it can lull you into a false sense of accomplishment--of thinking that you understand what you're reading when you really don't.
  3. The book should be exciting. I like crime novels, action-adventure, etc. Find something that sounds fun. If this is your first novel in the language, you'll need something interesting enough to get you through the first chapter. Young-adult novels may be a good compromise. They're only a little simpler than mainstream novels, and they're action-packed.
  4. The book should be contemporary. Books over 100 years old often use different grammar and/or spelling. Sadly, most of the free books on Amazon are old ones.
  5. The book should not be too hard. Literary writing uses a bigger vocabulary and often uses unusual grammar. Science Fiction often makes words up (some claim that this is offset by the fact that SF is otherwise simpler).
  6. The book shouldn't be too long. Under 200 pages is good. Over 500 is probably too much.
  7. The author should be one you haven't read before. Authors have favorite words and phrases that they reuse a lot. That's part of why the first chapter or two of a new novel is always the hardest to get through. But if you keep reading books by the same author, you're not growing. That said, if you really like an author, that can add a lot to your motivation to read.
  8. The book should be a professional publication. You do not want to be reading something with spelling or grammar errors in it! Almost all self-published books are really bad, and it doesn't matter what language they're written in.


Start by going to the foreign-language section of Amazon's US Kindle eBooks store. If you're in the UK, then visit the UK store.  Amazon Canada is more complex because French Books are listed separately from Foreign Books. In any case, look at the left-hand column and select the language you're interested in. That will then let you select the genre (e.g. crime stories, science fiction, romance, etc.) and finally you can look at the top twenty or so best sellers.

With that restriction, start at the top of the list and ctrl-click on every novel that seems like it might meet your criteria. This opens up a separate tab for each one. When you get to 10 or 15, go through them and discard any that don't meet the criteria above.

Now take some time and read the book descriptions on Amazon. Discard anything you're sure you wouldn't be interested in. (For example, I won't read anything that depends on some conspiracy theory being true.) Then have a look at the comments from readers--especially the three-star ones. To get more comments, go to Amazon's foreign-language site (e.g. amazon.es for Spanish) and read the reviews posted there. You can't buy anything from the foreign language site, but it's perfectly okay to read the reviews. Be suspicious of anything that doesn't have very many reviews. Goodreads is another place to look.

Of the books that remain, do Google searches for the titles and/or authors. See if they have Wikipedia articles that say anything positive about them. Look to see if they won prizes.

For any book that passed your screen, add it to a Wish List. Amazon lets you create private, named wish-lists to keep track of books you're thinking about but haven't decided to buy. Sleep on it. Review the list in the morning, and buy one!


Conventional Wisdom

Many people will tell you not to attempt a book if you need to look up more than five words per page. You'll get discouraged and give up. There is a lot of truth to this recommendation--it certainly describes my own pre-Kindle experiences. But I claim that advice is now out-of-date for the following reasons:
  1. A Kindle with electronic dictionary eliminates 99% of the work involved with dictionary lookups. That completely changes the equation.
  2. The notion of "a page" was always shaky (would that be a page from a hard-back book or from a paper-back book) but on a Kindle it makes no sense at all. Scholars studying reading usually talk in terms of words. To read a novel without a dictionary, you can only be confused about 1 or 2 words in 100. I would adapt this rule, then, and say that there should only be 1 or 2 hard words in every 100. That means words that take more than a few seconds to figure out even with the dictionary.
  3. If you use the old standard, there are almost no books that an intermediate student can read. The ones that are available are called graded readers, and they use a carefully restricted vocabulary. They're very expensive, they're rather boring (in my opinion), and there are very, very few to choose from. (Most of them are for people who are trying to learn English.)
  4. It makes more sense to estimate the difficulty after the first chapter. Unless it's really easy or the author is familiar to you, the first chapter will be by far the hardest. It's not good to give people reasons to give up so soon.

A Cautionary Tale

A friend or a teacher may recommend a book to you. You should welcome that, but check it out a bit before you read it. I'll illustrate just how bad it can be.

When I was a senior in high school, the teacher of my fourth-year Spanish class assigned each of us a novel to try to read over the Christmas holidays. She gave me La Gaviota by Fern├ín Caballero. For all the reasons I've described earlier, I failed to finish even the first chapter. Thirty-eight years later, I am still ashamed to admit that I lied to her about it, claiming I'd read it but that it was just really, really dull.

In the summer of 2014, after I'd mastered the technique of reading a foreign novel using a Kindle, I decided that after all these years I would finally make this right, so I bought a copy of La Gaviota and read it all the way through. Even with all the resources of modern technology, it took me weeks to finish it.  Part of the problem was that it was written in 1848 and the grammar and vocabulary were different enough to make quite a few sentences difficult to decipher. I eventually broke down and bought an English translation, which I consulted when all else failed. (The translation turned out to only cover the first half of the book, but fortunately I didn't need it after that.)

And it was awful. It's about a peasant girl whose talent for singing briefly lifts her to the top of Spanish society but whose selfishness and ingratitude destroys her life and the lives of those around her. There isn't a single likable character in the story. The book has an unfinished feel to it, at least by modern standards, because it has numerous plot elements that go nowhere and lots of characters who are introduced but never developed. Worst of all, the novel's message seemed to be that God was punishing her for rising above her place and punishing those her helped her do it. Yuk! (For a different opinion, read Eva's glowing review of La Gaviota.)

To add insult to injury, the book was actually a translation from French into Spanish, so it wasn't even an authentic Spanish novel in the first place.

On the bright side, I no longer feel quite so ashamed of myself. Mrs. Parker never should have assigned such a book to an 18-year-old boy. Not without strong guidance on how to read it, anyway.

So pick your novels carefully. If you like, you can review my own list of novels. These are books I've read, am reading, or thinking about reading.