Incidental Learning: How to learn vocabulary automatically

Incidental learning is something you do everyday. Learn how to use it for vocabulary learning. Photo by Jelleke Vanooteghem

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Imagine that you’re reading a novel – in French – say, Citadelle by A. de Saint-Excupéry. As time passes, you slowly crawl your way through a forest of unfamiliar French words, conjugations, and expressions. You can say that you’ve read more of your French-English dictionary than of the novel, but I bet that was Exupéry’s goal. What you want at this point, however, is to understand the book.

Understand the book, not to learn new vocabulary.

Nonetheless, since you can’t understand the novel without understanding the words of this novel, learning vocabulary becomes an essential part of reading. A part but not an ultimate goal, once again.

I bet you didn’t make a special list named  “500 words I learned from Citadelle“. You just check one word and keep going until you stumble over the next one. And although you don’t make any special effort to memorize all this vocabulary, your brain keeps track of it.

Should you be given a vocabulary test, you would perform quite well on both word recognition and word recall.

This phenomenon is called incidental learning.

What is incidental learning?

My best definition is the following:

Incidental learning is an example of the dark magic your brain does when it takes something from a situation where you didn’t mean to learn anything.

Now, attention… If you came to the conclusion that it is a totally unconscious process, you got in a trap set for you by the authors of linguistic and psychological terminology.

Incidental learning is not unconscious learning. You may be perfectly aware that you just learned a word from Citadelle. The main point here is that you didn’t have an intention to learn it. You had to learn it because you tried to understand the book.

If instead, you were scanning the chapter of Citadelle in search for unfamiliar words in order to cover a gap in your mental vocabulary, then we would talk about intentional learning. If, however, after reading Citadelle for pleasure, you came out with some ready-to-go definitions for “les vicissitudes” and “la vendange” wondering where the heck did these came from, it would be an example of fully unconscious implicit learning.

So keep these three separate.

How incidental learning helped you to learn 50000 words

How many words, you estimate, does include your English vocabulary?

According to calculations, high school students possess between 25000-50000 words vocabulary1. Now, do you remember explicitly learning 50000 words during the course of your life?

Probably not. And even if on your first anatomy class you were sitting and wondering what the heck the cerebellum is, you probably had it figured out by the end of the course. And even if you didn’t, you still may have a vague idea that it’s some part of the brain. All this just magically settled down without much of word lists, SRS programs or repeated chanting à la “cerebellum-cerebellum-cerebellum“. Whoa! How did this happen?!

Linguists believe that incidental learning is responsible for much of your 50000 words vocabulary. Somewhere in your teens, you picked up 10 new words every day without taking it any seriously. These words kept coming from your math class, from books you read and movies you watched and – at some point – even from the mouth of Vaas Montenegro from your favorite videogame.

All your life you were unconsciously experimenting with incidental vocabulary acquisition. Thanks to all those school tasks that forced you to deeply process, infer and internalize all those “metaphors“, “abscissas” and “predicates“.

And if it worked so well with your first language, can it help you acquire your second language vocabulary as well?

How to learn foreign language vocabulary incidentally?

Incidental learning works for second language acquisition as well. Moreover, it is often considered the best way to learn vocabulary in a new language.

Things are not that simple, though.

The long and fat body of linguistic research has indeed shown the effectiveness of incidental learning in all sorts of areas: from extensive reading, to narrow reading, to movie watching, to playing computer games. The formula is simple: engage in literally any activity in your target language and let your brain sort things out automatically. Substantial vocabulary gains are guaranteed.

For example, in their recent study linguists Stuart Webb and Elke Peters have found that after watching an hour-long documentary, learners acquired approximately four words. That’s a lot, comparing to another study where participants watched 10 TV episodes and gained only six words.2 Nonetheless, gains are gains.

What, are you already planning to watch 2-3 series of Money Heist in Spanish to learn 10 words per day?

Bad news for you, friend. Incidental learning is a tricky and unstable thing that highly depends on the ton of different factors, including your initial proficiency level.

What affects incidental learning of vocabulary?

There are three major factors standing in between you and effective incidental learning. Let’s sort these out.

Factor #1 Proficiency level

It may sound like Mark 4:25 but the more vocabulary you know the more vocabulary will stick to you while you do miscellaneous fun stuff in your target language.

It’s very hard to encode the first few hundred foreign words in memory. Your unfamiliarity with the linguistic system of your target language will just mess you up. Say you try to recall that Spanish word for “four” (which is “cuatro“). What you recall instead is a distant bell of some –atro on the background (I remember ending up with a Franco-Spanish mix of “quatro“). Or you will be visited by that vague feeling that you know how to say it but it just slipped your mind.

As British linguist Paul Meara puts it, incidental learning tends to work within the “low-high-low” framework. It translates into minimal efficiency for beginners (A1-A2), maximal efficiency for intermediate learners (B1-B2/C1) and again minimal for highly advanced learners (C2).3

This point is easy to explain. Beginners simply don’t have enough “core” vocabulary that would help them to figure out what on the Earth is going on in a book/movie/game. They also will have a problem parsing the content on important/unimportant. Highly advanced learners have already grasped all more-or-less frequent vocabulary, so they tend to ignore all this fluffy new stuff due to its obvious redundancy. You don’t need to know the word “bedraggled” if you know the word “wet”. Intermediate learners, on the other hand, take the full advantage of incidental learning. With the “core” words automatized, they can focus on filling the gaps and enriching their vocabulary on full speed.

Factor #2 Frequency

I were to create my own language learning pantheon, Frequency would be the goddess of painless vocabulary acquisition.

I mean, some words flash before your eyes so often that you just can’t ignore them. And I bet you don’t make any conscious effort but still end up memorizing them! This is something you really want to exploit. But there are only two options to do so.

The first option is to read, watch and listen to a lot of authentic target language content so that your brain automatically sorts out the most frequent words. Because the larger the data sample, the better the sampling.

The second option is to get a piece of authentic content where sorting was already done for you. Here come graded readers, children books, adapted literature and L2 textbooks filled with hand-picked “essential” vocabulary, meticulously dispersed along the lines.

Now, you might want to know how many times you need to encounter a word in order to learn it. Unfortunately, there is no formula. Despite this question being the favorite subject of linguistic research for the last ten years, nobody yet came up with a uniform answer.

What research is agreed upon is that Repetitio est mater studiorum.

Factor #3 Depth of processing

Let’s be honest, you don’t always turn to your dictionary when you see an unfamiliar word. Especially, if it is not essential for the meaning of the sentence. Come on, even Kato Lomb with her impressive baggage of 20-ish languages deliberately ignored the details:

It is much more of a problem if a book becomes flavorless in your hands because of interruptions rather than not knowing whether the inspector watches the murderer from behind a blackthorn or a hawthorn.

Kato Lomb, Polyglot: How I learn Languages

But… this approach has consequences. In the easiest case, you just end up not knowing a word. In the worst case, you actually end up knowing a word but under a wrong meaning. And in any case, this carelessness will cost you.

In 2001, two researchers Laufer and Hulstijn came up with “involvement load hypothesis”, which they considered the key to successful incidental vocabulary learning. The idea was simple: the more cognitive effort and motivation you put into establishing the connection between the form and the meaning of a word, the higher chances are that it will stick.4

And unlike all previous factors, this one is under your total control. There is a number of strategies to work your way up with incidental learning, especially when it comes to the depth of processing.

9 strategies for the top-speed incidental learning

Here is a sentence:

В глаза ярко светила луна: жирная и белесая словно червь луна.
The moon shined bright in my eyes: the fat and ??? like a worm moon.

Let’s me walk you through the Nine Circles of Hell Deep Processing.

Circle #1: Check the word form
It can be as dull as calculus class for a humanist. Nonetheless, the word form can give you some cues about the meaning. Here, we’ve got – look at that – an adjective. To be more technical: a singular, feminine Russian adjective.

Circle #2: Look at the context (if there is a context)
If you hated literary analysis in high school, just skip through. But I don’t recommend doing so because extracting the meaning from context is a powerful skill.
In this case, our adjective certainly means something disgusting. Moreover, it is a shared property of the moon and a worm. Hummmm…

Circle #3: Brainstorm for possible meanings
I mean… Imagine a worm. Imagine the moon. Give up and jump to the step #4
That’s the case when the context doesn’t actually give you enough cues to guess the meaning

Circle #4: Check in a dictionary
And so you open your fancy Cambridge Russian-English Dictionary, type the word in and discover that it means “whitish”. Yikes.

Circle #5: Practice pronunciation
There is literally 0% chance that you ever gonna use “белесый” in your everyday speech. Nonetheless, if you happen to encounter something useful be sure to check how to say that.

Circle #6: Write it down
No, seriously. Write the word in your language journal, create a flashcard in Anki or just save it with Readlang for future reference.

Circle #7: Use it in a sentence
When you write things down, keep them pinned to some context. Don’t just throw in space a card “белесый-whitish”. Try your best to write your own (preferably memorable) sentence containing this word – if the worm one wasn’t memorable enough.

Circle #8: Review it
Spaced repetition time! To make the most of your reading, stick to the SRS schedule and review this word. It will help you to remember it.

So you can do all this. It shouldn’t even take more than 20 minutes per word. 
Or you can simply check the word in a dictionary and use the ancient wisdom:

Circle #9: Commit it to memory
Mnemonic techniques like method Loci, for example, are naturally based on deep processing. So if you are familiar with Memory Palaces, be free to create an image of a fat whitish worm wraping around the moon and place it in your bedroom.

At this point, you may have begun to wonder if these 20 minutes word crusades are actually a part of incidental learning.

Can incidental learning still be deliberate?

If it seems to you that all this deep processing thing looks like very intentional and deliberate learning, you have a reason.

First of all, the review process certainly belongs to intentional learning activities. Sometimes, however, it happens naturally during reading when you simply encounter a word over and over again.

Second, incidental learning may include explicit memory and conscious thinking. And the deeper you go with your processing, the more your explicit memory is involved. And it’s all fine as long as you focus on reading/watching/listening for meaning.

Third, it is indeed merely impossible to go through all the stages of deep processing when you’re dealing with a novel, a movie or an hour-long podcast. It is impossible because the processing strategy was created for short stories like those in your textbook. With real books, you risk to crawl through the pages with the speed of a turtle and lose your initial “reading” intention on the way.

So how do you keep this balance?

How to keep the balance between efficiency and ease?

The strategy I use to keep things going is called Deliberate Filtering. And it’s a true antidote to the “blackthorn dilemma”.

When I see a word I haven’t seen before, I purposely ignore it for the first time. If it doesn’t show up in the next pages, I simply forget it. If it does repeat, I check it in a dictionary. This simple strategy helps me to filter out the vast amount of noise.

The point of this deliberate filtering, however, is to ignore the word just once. You can’t take advantage of frequency or incidental learning altogether if you see the word for the fifth time and still skip it.

Obviously, checking a dictionary is a cognitive pain including attention switching and refocusing. The real escape here is to use software that gives you an instant translation. I use Readlang, but you can always go with dictionaries like ABBYY Lingvo or even with Google Translate. Having the meaning of any word at your fingertips you can keep reading and learning vocabulary without losing momentum.

Obviously, it doesn’t have the same effect and doesn’t result in learning more words for a longer time. But:

Everything is a trade-off. The more you focus on details, the more difficult it is to decipher big ideas to take into your brain bank.

Sandra Bond Chapman, Make Your Brain Smarter

Out of three factors affecting incidental learning, frequency and depth of processing are complementary. Together, they make incidental learning extremely effective. But it is a heavy combo and a powerful pleasure-killing machine.

So drop one.

You can choose to ignore frequency and encode vocabulary with mnemonic techniques, so that you have minimal chance to forget it. Or you can drop the heavy stuff (deep processing) and bet on frequency alone to preserve the joy of reading (or playing a game, or watching a movie).

In any case, remember that it must be fun.

Author Details
Polyglot, Author and Founder of Linguapath
Hey! I am Alina Kuimova, and my long-lasting obsession with learning languages led to the creation of this site. Apart from being a grammar enthusiast, I enjoy reading smart books in any language available, finding easier ways for the brain to learn things and buffing productivity stats by 180%.
  1. Nagy, W.E., & Anderson, R.C. (1984). How many words are there in printed school English? Reading Research Quarterly, 19, 304-330.
  2. Peters, E., & Webb, S. (2018). INCIDENTAL VOCABULARY ACQUISITION THROUGH VIEWING L2 TELEVISION AND FACTORS THAT AFFECT LEARNING. Studies in Second Language Acquisition40(3), 551–577.
  3. Hulstijn, J. H. (2001). Intentional and incidental second-language vocabulary learning: A reappraisal of elaboration, rehearsal and automaticity. Dans P. Robinson (Ed.), Cognition and Second Language Instruction (p. 258-286). Cambridge: Cambridge University Press.
  4. B Laufer, J Hulstijn; Incidental vocabulary acquisition in a second language: the construct of task-induced involvement, Applied Linguistics, Volume 22, Issue 1, 1 March 2001, Pages 1–26,
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