Changes to the scheduling algorithm?

Hey guys,

I woke up with 157 reviews this morning. That’s close to twice my all-time high, and about five times what I’ve been reviewing recently.

Have you changed the algorithm, or did I hit the spaced-repetition jackpot today?

Hey Trent,

The short answer is that we haven’t changed the algorithm lately, and what you’re seeing is typical. I’ve been meaning to write a full-blown blog post on this anyway, so I’ll give you a teaser here! :books:

Due to the nature of spaced rehearsal systems (SRS), your workload tends to compound as you learn more material, and the quantity of material for any given day does ebb and flow. The secret to minimizing your study time can be counterintuitive: slow down, focus, and do all the quizzes on a regular basis. This will maximize your retention, increase your percentage of correct responses, lengthen your review intervals, and will essentially make the items you know drop out of your queue faster so you can give the harder concepts the time they deserve.

Everyone has different study patterns and preferences, and they’re much more varied than you’d think. Building an effective study platform to support all these use cases has been an interesting challenge for us. We have an enormous amount of study data we’ve collected over the years, but basic analysis tends to yield no insights because of the huge variance in virtually every metric. That said, time spent per review quiz is actually one of our more normally distributed data points.

On average, Achievable users tend to spend about 15 seconds per review quiz. So while that stack of 150+ reviews is certainly daunting, if you sit down, focus, and power through it, you’ll be done in less than an hour. Try to make studying part of your routine, and turn downtime into productive time. After you wake up, during meals, in transit, or before you go to sleep are all great opportunities to consistently put in study time.

Our learning engine technology is advanced and is a big part of our special sauce so I can’t go into much detail on how it works, but I can talk about some of the key concepts involved. Nearly all SRS-based sites use something called a Leitner system. The core concept is pretty simple - study at the designated intervals, and roughly speaking, your retention will double at each interval.

However, Leitner systems are only accurate if you study close to the designated time. If you’re cramming for your exam and want to re-review the content quickly, or if you take a vacation over a long weekend and don’t study, the intervals get all messed up and might end up creating extra work for you, or worse yet, might deprioritize content that you still need to review. I’m still a big fan of Leitner-based SRS sites and use several myself for foreign language learning, but I always have a hearty laugh when I see features like “vacation mode” that let you “pause” the SRS. Memory decay doesn’t care if you’re taking a break to enjoy that sunny beach or ski trip :beach_umbrella: :skier:

Achievable’s proprietary learning engine was built from the ground up to handle a wide variety of study patterns. Rather than using the simple approximation of the Leitner system, we dove deep into memory science research and implemented very accurate models of retention and decay. With us, you can study any content at any time, and we’ll update our model of your personalized memory accurately. And by leveraging the trove of student memory data we’ve collected, we’ve validated our learning engine by replaying historical data to ensure the results line up.

I might be giving away a little too much here, but this is so interesting I feel I have to share it: our system is designed for you to get a certain percentage of items wrong. You’ve heard your teachers say that making mistakes is part of the learning process, and our research backs this up. So that last mistake might not be on you, but rather on us :smirk:

Finally, I want to highlight that while Achievable is an extremely effective study tool, it is still just a tool. There is no silver bullet to passing your exam; you still have to get serious and put in the time. Our mobile-friendly platform, easy-to-understand content, and advanced learning engine will help you get there effectively and efficiently, and our team is here to support you, but at the end of the day you’re the one most responsible for your own success. So when you do pass, thank yourself as well as us! :smiling_face_with_three_hearts:



Thank’s Justin, that was very helpful.