Welcome to another week of Dear Duolingo, an advice column just for learners. Catch up on past installments here.

Hi there, learners! A few weeks ago, we mentioned mistake patterns in language learning—and hundreds of you immediately wrote in asking for more information. I'm not sure we've ever received so many messages, so quickly, about the same topic! Here is one representative question:

This week's question keeps it simple:

Dear Duolingo,

Mistake patterns info plz!


There are actually 2 kinds of mistake patterns we could talk about: those that are common to learners no matter the language they're studying and those that are language-specific. We'll get to the language-specific patterns another week… because there's so much to say about the universal patterns!

These patterns are the result of all of us coming to the learning task with the same machinery (brain, mouth, hands, tongue, etc). They reveal something about how our brains process new languages—what they pay attention to, what is hard to focus on, how we figure out meaning—and how our old and new languages interact with each other in our head.

One thing to keep in mind is that these patterns are what language researchers have observed for decades across learners, course types, and language experiences. Mistakes are a natural part of learning, no matter how or what you study!

Here are 8 mistake patterns that learners of all languages face:

🎢 U-shaped learning

One pattern all learners are susceptible to is called U-shaped learning: Learners start by doing something accurately, then they get worse at it (!!), then they return to using it accurately again. (Get it? They start at the top of the U, then sink down to the bottom, and then they go back up.)

Early stages of learning often involve remembering words and phrases as single chunks: You learn what to say, but you don't really understand the grammar rules behind it. As you learn more grammar, your brain has to make the new information work with the old chunk it had memorized. It develops hypotheses about what must be happening—and inevitably, certain (wrong) hypotheses become natural choices to test out. Then those mistaken hypotheses get replaced, again and again, until you land on the more complete, adult-like use of that chunk—complete with intuitions about the grammar behind it.

This pattern is something we see for both first and second languages:

  • Children learning English as their first language: When they are toddlers, English-learning kids will use I went accurately (I went to the store with Daddy) because they've learned it as a chunk—they group it together like Iwent. Then they start to catch on that you put -ed on the ends of verbs for past tense, so they start using that pattern (I goed to the store with Daddy). As they keep gathering data and hearing more language, they realize that go is irregular and they might say I wented. Finally, after more data and pattern-analyzing, they'll start using I went again—they've fully acquired how to form this irregular past tense (without ever knowing what it’s called)!
  • Adults learning Spanish as a new language: Very early on, students learn Me llamo ("My name is," but literally "I call myself"), and they remember it as a chunk: Mellamo. As learners see more Spanish and start learning about verbs, they realize that llamo must be a verb with an -o ending… but at this early point it's still unclear what that me is doing. Learners often cycle through variations like yo llamo (after all, that's how you form other verbs, right?), mi llamo (maybe the structure is actually "my name," so it should be mi?), and mi llamo es (a true mix of hypotheses about nouns and verbs, as they learn more and more Spanish). After seeing enough examples, and also learning more about reflexive verbs that use me, learners get back to the accurate Me llamo.
Illustration of Duolingo character Zari floating in space

👯‍♀️ Generalization

Because our brains do all that data collection and hypothesis testing, we love landing on a rule that works… and it's easy for us to overapply it! For example, both English-speaking kids and adult English learners will learn that adding -s to a noun makes it plural: cat-cats, dog-dogs, house-houses, bottle-bottles, etc. What a great rule! Except, of course, there are all kinds of exceptions, and young and old learners alike are apt to also say childs, gooses, tooths, foots, etc. Sigh… guess that hypothesis needs to be revised. 😉

⚖️ Preference for content-full words

Our brains prioritize content-full words over grammar words and endings, so sometimes we don't totally process those parts of grammar! For example, in English, a word like yesterday lets us know that something happened in the past. We also use the ending -ed to show past tense, so in a sentence like Yesterday we walked to the store, there's 2 bits indicating past tense: a content-full word like yesterday and the grammatical ending -ed. This means that learners' brains will process yesterday and possibly ignore the -ed since they both have the same meaning! That's why you might see more clues like yesterday in earlier lessons when you're first learning -ed… and eventually you have to get used to focusing on those endings alone.

📰 Better processing for new information

We also process the most meaningful words and parts of words before bits of grammar that don't add new information—so learners definitely have a cognitive reason to dread grammatical gender! Prefixes and suffixes that do add new information, like the un- in unlikely, will be processed more deeply than the -s on verbs like walks. (There are also other reasons why the English -s verb ending is so hard for learners!)

🥇 Importance of the first noun

Our brains also tend to assume that the first noun we encounter in a sentence is the subject, the person or thing doing the action of the verb. In English, this will often get you the correct understanding of the sentence, since English subjects come before the verb, but it can also trick you, too.

For example, in a sentence like The cat was chased by the dog, it's true that the cat is the grammatical subject of this passive sentence—but because we also focus more on chase than on the was or the -ed ending uses for passives, it means that learners are tempted to think that the cat did the chasing, since the cat is the first noun. (And if you're learning a language with more flexible word order, there's even more room for confusion!)

⏰ More attention early in a sentence

Even beyond the first noun, in general learners direct more attention to the early words in the sentence and are more likely to process those words more deeply than words, prefixes, and suffixes occurring later in the sentence. Our brains sort of run out of steam later in a sentence… but of course, there's going to be important grammatical information tucked away at the end, too!

🤔 Relying on real-world information

When understanding a new language, our brains use all the resources at our disposal to figure out meaning, including some strategies that don't even really involve language! We incorporate our knowledge of the world in general and the particular context in which we're using the language to help figure out the meaning of words and phrases and to learn the smaller bits of grammar.

For example, if you heard The cat was chased by the mouse in your new language, you might use what you know about cats and mice to deduce who is more likely to be doing the chasing—even though in this particular sentence, that conclusion would be wrong! Similarly, if you heard The chair was chewed on by the dog, even if you weren't totally sure about the word order or the grammatical endings, your real-world knowledge tells you chairs don't chew things, so your attention is directed away from that interpretation. You can see how many of these principles will interact in complex ways to understand even relatively short sentences!

Our natural reliance on probability is part of the benefit of encountering some silly sentences in Duolingo lessons: You really need to focus on meaning and the actual words and grammar in the sentence to reach the right interpretation.

We have to drag your brain away from just relying on that tempting real-world knowledge and skipping the grammar!

♻️ Language transfer

In addition to all these tendencies that have to do with how our brains focus on and attend to new information, there's another big factor to consider: We already know (at least) one language!

We mostly use the same parts of our brain to process our first language and ones we learn later on, so it's natural for our brain to apply rules, sounds, and grammar from a language we know to the language we're learning. In practice, that might mean putting words from the new language in the order of our first language, speaking with an accent, and leaving out words or endings that we're not used to using in our own language (like how Spanish and Italian don't require saying the subject pronoun, but it's necessary in English).

Let learning run its course!

Making mistakes in a new language can feel frustrating, but it's totally normal! Going through these stages is just part of learning this amazing and maddening new skill. Practicing can help you move through the stages faster, but you're at the mercy of your brain. Let it do its thing! 🧠

For more answers to your language and learning questions, email us at dearduolingo@duolingo.com.