The idea of measuring fatigue seems worthwhile, but I have the following question: for what? For information?
My thoughts on this matter:
“Anki is a program which makes remembering things easy” through spaced repetition. So, how should this ‘fatigue’ affect the intervals?
Var 1: Man, you’ve marked 10 mature cards in a row as ‘Again’. Yes, maybe you really forgot them, but maybe you’re just tired and need to rest? Let me suggest you take a break (I’ll show a notification) and I won’t count your answers on these 10 cards so as not to mess up your FSRT statistics? If so, we have a deal. If not, and you really think you forgot them, then okay, let’s continue studying.
Why do I think it’s necessary to measure only mature cards? Because with learning cards, we can’t determine the cause: the user’s fatigue or the complexity of the cards.
Var 2: The fatigue indicator should somehow influence the calculation of the next intervals for showing the card. But I don’t know what function to use since the user’s fatigue for Anki is practically a random variable.
Var 3: Base it on the time taken to answer. I think you’ll agree that we actively try to recall the card in the first 20 seconds. You either know it or you don’t. So, if at the beginning of the session you had good speed, but over time you slow down + var 1 – I think the answer is obvious, you’re tired.
Perhaps! it’s worth taking into account the session start time and comparing it to the user’s historical data since each user is unique. Yes, most likely, over time, an average statistic will be established (like, ‘it’s better to study cards right after waking up’) and thus influence with a weight coefficient, but this is a research task.
In the end, in my understanding, Anki should recognize that if a person is tired, at this moment, in this session, there’s no point in showing them cards because the effect will be minimal.
It’s case not about finding those specific time windows when the brain is working at 100%.