The Forgetting Curve
The forgetting curve is a model that shows how well we retain information based on how much time has passed since we learned it. It was discovered by Hermann Ebbinghaus in 1885 and basically, it shows that the amount of information we remember decreases exponentially until we remember almost none of the material.
Ok, so you may feel like this theory helps explain how quickly you forget material you literally just learned, but knowing that the forgetting curve exists can’t actually help you remember things, right? Wrong. The thing about the forgetting curve is that it is able to be overcome. Hermann Ebbinghaus proposed that in order to best retain information and overcome the forgetting curve, learning should be spaced and repetition of learned material should be frequent.
As soon as you learn material, your memory of it will decrease until you remember almost none of it. For example, material that you learned at the beginning of the year feels completely foreign when you're studying it for final exams. But, if you review material frequently after you've already learned it, it will still be familiar enough as you're reviewing it so that you fully understand it, and the repetition will obviously strengthen your memory so that it will take you longer to fully forget the information.
What Hermann Ebbinghaus' discovery can teach us is that when you learn some information in class, do not just shove it in the back of your mind until it's time to study for exams. You should make sure to repeat the information frequently, so that it will become ingrained in your memory.