Overview
For a description of WaniKani’s SRS Mechanics, see: How long between reviews
After using this site for a few months, I’m quite happy with my progress, but I have had some lingering doubts about certain correlation-related aspects of the review scheduling system.
The mechanics lead to the following behaviors (not technical definitions):
- Grouping: Lessons are usually completed in batches and tend to be reviewed together. As long as they are reviewed together, then these items will remain in the same review group. Review groups provide context to items in the same group as well as in relation to other groups.
- Unlock Ordering: As we know, radicals unlock kanji, which unlock vocabulary. If you consistently review your items, you will generally see a “radical → kanji → vocabulary” order to your reviews with gaps of 3 to 4 days between them. The review mechanics cause review items to remain fixed to their unlock ordering.
Are certain aspects detrimental? Beneficial? What options could be provided to improve the user experience?
Grouping
Items within a group provide context for other items in the same group. After seeing some items in a review session, it becomes easier to predict the answers for the rest of the items in the same review. If one can consciously or subconsciously identify a group, one can also rule out members of other review groups.
For example, when learning kanji, you might recall that there were 2 kanji named “death” or that 3 of them had "しょう” as onyomi readings.
While some radicals or kanji look like each other, it isn’t too hard to differentiate if you can vaguely remember the levels they came from. For radicals, it might be very hard to mix up “bed” and “snake”, since the snake radical definitely came after bed.
Good: Grouping makes it a little bit easier to recall items during the apprentice levels. This boosts early accuracy.
Bad: WaniKani’s intent is to have you type in your answer (recall, not recognize), but grouping makes reviews a lot easier than intended. Grouping can be used as a crutch, which can lead to unexpected lower accuracy at later SRS stages (Master, Enlighten).
Mitigations: Reviews come out of order, and often, they get mixed in with a ton of other items. If a user can burn items based on Grouping alone, that user will probably be okay. In other words, the bad might not matter in the long run.
Unlock Ordering
Reviews follow a predictable schedule, so they will tend to follow the “unlock ordering” (radicals → kanji → vocabulary) with about a 3 to 4 day gap. Users on the forum have said it’s bad practice to specifically review items before you are about to get them in a WaniKani review, so this rigid order might pose a problem.
Good: It could be argued that the reverse ordering (vocabulary → kanji → radical) is worse; the mnemonics make it much easier to recall the dependent items. At the very least, “unlock ordering” guarantees that we don’t prime ourselves in an obviously bad way.
Bad: Even if “unlock ordering” is better than the reverse order, wouldn’t it be better to have no correlation at all? This order still primes memories a little more than necessary.
Suggestion: Randomized Review Delays
For the most part, I think that the early cycles don’t need changing and that users should have a choice if they want to do anything about these problems.
Randomized Review Delays: Allow users to set a preference where later-stage SRS review items will receive a randomized review delay. Rather than using the exact SRS delay, reviewed items may incur a random increase or decrease in days. (The expected value of the randomized delay can equal the existing delay.)
Randomness avoids the “grouping” and “unlock ordering” phenomena; both of them are derived from how strongly correlated reviews are. Since the hour and day differences matter much less after Guru, it should be relatively safe to do this.
Optional: Allow randomizing over hours, not just days.
- Good: Better load-balancing and review mixing. A lot of users prefer a more even review distribution.
- Bad: Pretty much every hour will have a review. Those who don’t review at fixed times may find themselves checking WaniKani constantly. Ultimate Timelines will be trashed.
Conclusion
While I do trust in the SRS system, the way it is setup leads to too much correlation between items. Overall, I think it would be beneficial (but not necessary) to provide users with more control over review timing. One suggestion is to randomize the review delay for later-stage SRS items.
It probably should also be stated that WaniKani shouldn’t be your only learning source. If WaniKani is supplemented with natural language practice, the issues I’ve highlighted might not amount to anything significant at all.
If you’ve read this much, I hope you’ve found my perspective interesting. Please discuss and share your thoughts on this topic!
It’s certainly not what I’d want to do either.