If you stop speaking English now, you will eventually completely forget it.

It might take several decades of you not uttering your native language, but at the same time it’s normal: What you don’t use will be forgotten. It will vanish, as happened with all those important history dates you had to learn in school. (We had to memorize plenty, but I can only recall just a few.)

But there’s a flip side: when you will forget something can be predicted. And that’s how Vocab Ninja lets you study just enough, reviewing cards only when you’re about to forget them.

A walk in the Costa Rican jungle

Imagine this happened when you were five years old: you’re on a holiday in Costa Rica with your parents. They have all kinds of activities so they often drop you off at the resort’s children’s club. You hate it. The nannies only speak Spanish. So after some nagging and whining, your parents decide to take you along the next day. On the program is a jungle expedition.

Forgetting curve of you still remembering how to speak, after being abducted by friendly monkeys in the Costa Rican jungle

Hey, things like this do happen. But a lot more common than this Tarzan scenario is people forgetting their native language because of living in a foreign country for decades.

Forgetting your native language? Hard.

I remember seeing it on a news bulletin some years ago: a WW2 prisoner of war had never left Japan. For some reason he had stayed there, lived there, and now he was returning to the USA for the first time in more than 60 years. The gathered press at the airport bombarded him with questions the moment he walked through the gate. He could not reply. He did not understand any English. His native language was gone.

It’s not uncommon to lose parts of a language because of lessened exposure; it’s called language attrition. I have experienced it myself. When I’m out of Belgium for a while (I live abroad most of the year) I tend to speak Dutch only when calling friends and family. And during those calls a stupid, common, everyday word might be on the tip of my tongue. It’s like parts of Dutch were moved to a self-storage unit because there wasn’t enough room in the apartment.

Still, it takes many years to completely forget something as ingrained as your native language. It’s a lot easier to forget a language that you’re still learning.

Forgetting a new language? Easy!

Did you know that the French for ‘monkey’ is ‘un singe’?

Me neither. Well, let’s try to remember it.

Forgetting curve of fresh bit of information, heard only once.

The possibility of you and me still remembering this will drop rapidly. There’s only a one-in-two chance that we will still remember this tidbit of useful information in a few weeks. But this also depends on how much you would like to remember it, so I’ll probably forget it even faster. (I had the worst grades for French in school. I have no interest in learning it.)

But sometimes you’re obliged to remember stuff, like for an exam. So what do you do? You study it more. You review the material more often. You cram.

Forgetting curve after cramming for an exam

As you certainly have experienced, you will still forget most of the material once the exam is over. And that’s okay; it probably wasn’t worth remembering anyway.

But when you are studying something that you would like to remember for the rest of your life (like words in a new language), you should do it differently.

Learning without forgetting

When you review things regularly, you retain them better. The few days of cramming in the example above did help you remember the facts better afterwards. The curve tapered off slower than the first curve (where you learned that ‘un singe’ is a monkey only once).

When you already know things for a while you tend to forget them slower; they start to stick.

This forgetting curve (figured out by Hermann Ebbinghaus) can be predicted. This means that we can figure out when you will forget something and have you review it only at those times, and not earlier.

These are the intervals Vocab Ninja will use:

An optimal spaced repetition schedule

So, 3 days after you answered a card correctly you will see it again. Still remember it? It appears 7 days later again, then again in 17 days, and so on.

This is exactly what Spaced Repetition Software (SRS) does: It lets you study facts as efficiently as possible. I’ve written more in detail about the different kinds of spaced repetition (Leitner, SRS, SRS+) on flashcardapps.info.

Vocab Ninja is an ‘SRS+’ so it also takes the difficulty of a word into account when planning the next review date: An easy word will be reviewed less, a difficult one more often.

Other SRS+ apps use a set of buttons for rating how difficult a card was (like: ‘Didn’t know,’ ‘Good,’ ‘Easy,’ ‘Very Easy’). Vocab Ninja just looks at the amount of time you had to think before answering; I think not having to decide which button to tap is a better user experience.