（如果学习材料有困难）典型的间隔重复记忆系统[1]会干两件事：缩短下一次复习的时间间隔，并且（通常）要求学生稍后对该卡片重新作答（SRS 重试机制）。
Sana Labs 会重新引入卡片材料的源文章，或是建议（「也许你想要重读这篇文章？」）或是直接在下一次复习环节中，安排阅读这篇文章（「这篇文章的内容对你而言有些困难」）
由于助记媒介[2]将卡片与源文本紧密联系在一起，助记媒介可能有更多选择：可以将源文章特定部分摘录下来，或者让读者回到源文章阅读。
其他可能性：
- 增添材料的变体，来夯实记忆
- Duolingo 可能会这样做？我无法判断。
- 引入一些针对单张卡片理解困难而编写的材料
- 为寻求他人帮助提供便利
但是，至关重要的是：间隔重复记忆系统中，需要根据卡片回答错误的原因确定干预手段[3]。
文献
队列
- Butler, A. C., Godbole, N., & Marsh, E. J. (2013). Explanation feedback is better than correct answer feedback for promoting transfer of learning. Journal of Educational Psychology, 105,290–298. http://dx.doi.org/10 .1037/a0031026
- McDaniel, M. A., Howard, D. C., & Einstein, G. O. (2009). The read- recite-review study strategy: Effective and portable. Psychological Sci- ence, 20, 516–522. http://dx.doi.org/10.1111/j.1467-9280.2009.02325.x
- McDaniel, M. A., & Little, J. L. (in press). Multiple-choice and short- answer quizzing on equal footing in the classroom: Potential indirect effects of testing. In J. Dunlosky & K. Rawson (Eds.), Handbook of cognition and education. New York, NY: Cambridge University Press.
- Pan, S. C., Gopal, A., & Rickard, T. C. (2015). Testing with feedback yields potent, but piecewise, learning of history and biology facts. Journal of Educational Psychology, 108, 563–575. http://dx.doi.org/10.1037/edu0000074
- Pan, S. C., & Rickard, T. C. (2017). Does retrieval practice enhance learning and transfer relative to restudy for term-definition facts? Jour- nal of Experimental Psychology: Applied, 23, 278–292. http://dx.doi.org/10.1037/xap0000124
- van Eersel, G. G., Verkoeijen, P. P., Povilenaite, M., & Rikers, R. (2016). The testing effect and far transfer: The role of exposure to key infor- mation. Frontiers in Psychology, 7, 1977. http://dx.doi.org/10.3389/fpsyg.2016.01977
链接至本文（已汉化）
声明
此内容发布由 Andy Matuschak 许可。未经允许，不得转载或修改。保留所有权利。
Thoughts Memo 汉化组译制
原文：How might spaced repetition memory systems intervene when the student struggles with material? (andymatuschak.org)
参考
1. 间隔重复记忆系统 ./404257681.html2. 助记媒介 (Mnemonic medium) ./459483765.html
3. 间隔重复记忆系统中，需要根据卡片回答错误的原因确定干预手段 ./560444821.html