Monday, July 29, 2013

Why I use flashcards (and you should too): Learn more with flashcards than without

There are two main reasons why you should use flashcards. The first is that, with a spaced-repetition system, they allow you to learn more quickly than exposure alone. I'll turn to that in my next post.

The second reason—and the one I'll cover in this post—is that they let you learn words that you otherwise wouldn't be able to learn.

Let's look at how this plays out in terms of numbers. To give us some goal posts to consider, I'll use the rough numbers that Alexander Arguelles uses to break down languages' levels of vocabulary, i.e., the top 250, 750, 2,500, 5,000, 10,000 and 20,000 most-common words. Wiktionary's 2006 TV and movie script frequency list will provide us with some concrete numbers to apply to those levels.

First, to give us an idea of how frequently the words around each of those milestones appear, let's see how many times the 250th, 750th, 2,500th, etc., words appear in the TV and movie scripts:

Nth most-common word: 250 750 2,500 5,000 10,000 20,000
Number of times it appears: 14,765 3,224 653 236 77 24

So nothing surprising here; the more common the word, the more times it appears in the TV and movie scripts.

Now let's take that one step further by making a couple of assumptions:
  • First, let's assume that the TV and movie scripts are the same as what a native speaker might encounter on a typical day. It's hard to say whether these numbers would match up with what a native speaker typically encounters (are scripts dumbed down to the lowest common denominator or are they more flowery because of all the English majors writing scripts?), so we'll just set that debate aside and take it as good enough.

  • Second, let's assume that the 750th most-common word is used exactly once per day, those less common are used less than once per day, and those more common are used once or more per day. This assumption is based on Alexander's estimate that the 750 most-common words are those that native speakers use every day.

Using those assumptions, we can work out how many days there will be between a native speaker's exposures to a word at a given frequency.

Nth most-common word: 250 750 2,500 5,000 10,000 20,000
Days between exposures: 0.2 1 5 14 42 134

Let's generously assume that the average time it will take you to completely forget something is 2 weeks, or 14 days. If you completely forget something, the next time you see it you are effectively starting from zero. To learn something, you need repeated exposures to it (approximately 15 to 20 exposures). However, if you completely forget something, you're always starting at zero and no subsequent exposure would ever count as a repeat.

Thus, you'll be limited to learning whatever gets repeated in 14 days or less. Based on the numbers above, that would eventually put you somewhere around 5,000 vocab words, which Alexander describes as being the rough active vocab of an uneducated native speaker. Not a terrible goal if that's what you're looking for—and not surprising considering that this is exactly the kind of exposure an uneducated native speaker would get.

But—and this is a big but—the numbers above assume you're getting as much exposure to the language as a native speaker. Let's conservatively say that a native speaker gets 8 hours per day of meaningful exposure to his or her native language. Let's also ignore the fact that, as a non-native speaker, much of your exposure to the language will only be meaningful after you spend the time to look things up, which will mean that you'll get less meaningful exposure per minute of exposure than a native speaker would.

If you're not getting so much exposure, it becomes much harder to get the requisite number of exposures to commit something to memory. Let's look at what happens when you get less exposure than a native speaker, e.g.:
  • 4 hours, or 1/2 of our hypothetical native speaker's exposure, which would be a very decent amount of exposure to be getting outside of the country where the language is spoken.
  • 2 hours (1/4), which might be the amount you're getting if you are being tutored and complementing that with some studying on your own.
  • 1 hour (1/8), which might be typical of someone studying on their own while work and the rest of their life continues.

Nth most-common word: 250 750 2,500 5,000 10,000 20,000
Days between exposures @ 8 hrs/d: 0.2 1 5 14 42 134
Days between exposures @ 4 hrs/d: 0.4 2 10 27 84 269
Days between exposures @ 2 hrs/d: 0.9 4 20 55 168 537
Days between exposures @ 1 hr/d: 1.7 8 40 109 335 1,075

Assuming again that, on average, you need to see something at least once every 14 days to put it to memory, things suddenly get a lot harder. With 4 hours of exposure per day, you'll still be past the 2,500-word "survival" milestone, but 5,000 words is out of reach. At 1 or 2 hours per day, you can't even reach the 2,500-word milestone. (As an aside, you might get an hour or two of exposure per day when taking a class, which jibes with the fact that classes alone typically never even get you to the survival level…)

So how do we go about getting more exposure to words than we otherwise would naturally? I think you know where I'm heading with this…


Flashcards, or—more accurately—spaced-repetition systems, are designed to do just that. They provide you with systematic exposures to words that you otherwise wouldn't get with enough frequency to commit to memory.

If you're content with the limitations of what you can learn from exposure without flashcards, that's a low bar, but it might work if your language-learning goals are relatively modest and you have a lot of time to commit to language learning. But if your goal is to try to approach the level of a native speaker in as little time as possible, you're leaving lots of learning on the table if you choose not to use an SRS.

This post is part of a series on using flashcards written in response to Why I don't use flashcards (and you shouldn't either) and other related posts on
  1. How to use flashcards the right way
  2. When to use flashcards
  3. How much to use flashcards
  4. Learn more with flashcards than without
  5. Learn faster with flashcards than without
  6. Translation is not the end result of flashcard use
  7. How to deal with the lack of one-to-one translations

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