Ask HN: Algorithm to help humans learn?

So, I'm building a simple flashcards/memorization game and would like to boost it further by helping people learn.

Is there some study/algorithm that correlates the times you have seen something, the time to learn, the frequency and distance of when you last saw it(something you've seen yesterday is easier to remember than something you've seen 2 years ago).

Could be something simple, just to start off. I tried to google it, but it's hard. Algorithms and learning always end up with something about "teaching computers to learn/AI", when I actually want to help humans...