The most obvious way to use a Spaced repetition memory system is to memorize simple facts: names, definitions, numerical constants, etc. The vast majority of memory system users appear to only ever use them for this purpose. But spaced repetition isn’t just useful for memorizing simple facts. The same mechanism can be used to deeply understand complex material, particularly if you write our own prompts (How important is it to write your own spaced repetition memory prompts?). Such conceptually-oriented prompts might test you on connections, implications, causes, consequences. These broader ideas don’t naively feel like facts which can be memorized—but they often are. Besides the benefit of memorizing these conceptual ideas, engaging with higher-level relationships in this way over time can keep you in contact with the topic and help you internalize it more deeply. (related: The mnemonic medium keeps readers in contact with material over time)
Writing good spaced repetition memory prompts is hard; writing good conceptual prompts is much more so. The techniques used to encode abstract, conceptual knowledge are not well or widely understood. See Important attributes of good spaced repetition memory prompts for more. Particularly relevant here: Spaced repetition memory prompts should encode ideas from multiple angles.
This is one important retort to Many people view memory as unimportant to deep creative work.
It’s worth noting, too, that the cogpsy basis of spaced repetition (the Testing effect) has been demonstrated for conceptual knowledge as well as for declarative knowledge (see Karpicke and Blunt, 2011). But should you practice integrative tasks for conceptual learning instead of atomic tasks (per Spaced repetition memory prompts should usually focus on one atomic unit)? Probably, at least in part: How complex should tasks be for test-enhanced learning?
It’s possible that this type of information may be much “cheaper” to remember with spaced repetition schedules: Conceptual information may have much slower optimal spaced repetition schedules.
Butler, A. (2010). Repeated Testing Produces Superior Transfer of Learning Relative to Repeated Studying. Journal of Experimental Psychology. Learning, Memory, and Cognition, 36, 1118–1133. demonstrates the Testing effect for conceptual questions as well as factual questions
Karpicke, J. D., & Blunt, J. R. (2011). Retrieval Practice Produces More Learning than Elaborative Studying with Concept Mapping. Science, 331(6018), 772–775 demonstrates a substantial testing effect for conceptual questions.
Matuschak, A., & Nielsen, M. (2019, October 0). How can we develop transformative tools for thought? https://numinous.productions/ttft (see https://numinous.productions/ttft/#how-important-is-memory for more arguments around this topic)