>I'm not so sure about the spaced repetition side of things.
From what I could read, many studies have shown this is an effective technique. From my personal experience it only works if you understand what you are trying to remember. For example, trying to memorize some complicated formulas that you don't understand is doomed to fail.
I think you misunderstand. They aren't doubting SRS. They're doubting that MathAcademy is doing it. They logged in after 2 weeks and had no reviews waiting.
Just a heads up that there's an explanation for this; I responded to the original comment (https://news.ycombinator.com/item?id=41556644) but I'll also paste here in case anyone misses it:
1. New tasks are selected only as you complete existing tasks (so if you come back after 2 weeks, you need to complete some existing tasks from 2 weeks ago to get new tasks selected based on your knowledge profile right now).
2. We are often able to implicitly knock out due reviews with new lessons. We're not just doing plain vanilla spaced repetition. We're doing a highly efficient novel version of it that we call Fractional Implicit Repetition (FIRe). I have a writeup on this that gained some traction on HN recently: https://news.ycombinator.com/item?id=40954571
From what I could read, many studies have shown this is an effective technique. From my personal experience it only works if you understand what you are trying to remember. For example, trying to memorize some complicated formulas that you don't understand is doomed to fail.