I recently stumbled across some pretty interesting data on how quickly we forget things depending on how we were exposed to those things. From a post by AJ Kumar called "You Forget 80% of What You Learn Every Day!":
We learn:So how do the four core skills of the language-learning trade—reading, writing, listening, and speaking—fare in the above?
- 10% What we READ
- 20% What we HEAR
- 30% What we SEE
- 50% What we SEE and HEAR
- 70% What we DISCUSSED with OTHERS
- 80% What we EXPERIENCED PERSONALLY
- 95% What we TEACH TO SOMEONE ELSE
Well, reading alone is obviously at the 10%-retention level, and listening to something will boost that a bit to 20%. Seeing and hearing together results in a 50% chance of recollection, so it's probably safe to say that reading and listening together would be better than either alone. So, for example, you should add audio to your flashcards.
Where writing and speaking fall is less clear. As reading, hearing, and seeing are all passive activities, writing and speaking—as active activities—should result in more retention. Speaking might be part of "what we discuss with others", but, when you're dealing with a language, the language is usually the medium of communication and not the subject of discussion, so it's unclear if the "discussion" concept would apply in the same way, and I'd wager that it probably wouldn't. So the level of retention for something you've written or spoken probably falls somewhere above 50% (seeing + hearing) but below 70% (discussion).
So, to boil the numbers down above to the four core language skills (with some off-the-cuff estimates so we can have some pretty numbers to look at):
We learn:At a glance, these ballpark figures seem about right. Certain spaced-repetition systems' data seems to point to 10% retention, which would make sense given that most of that data is read. Hearing does seem to increase the likelihood of retention, and I've found it easier to retain knowledge when a flashcard contains both text and audio as opposed to containing just text. And, lastly, once you've been able to write or say something (caveat: correctly!), you're of course much less likely to forget it.
- 10% What we read
- 20% What we listen to
- 30% What we read and listen to
- 60% What we write or say