Not inherent to the effect; you can get the spacing or testing effects without providing the right answer or measuring the response.
I think it's very inherent to the supermemo algorithm. Otherwise how does learning without spacing looks like?
I think this got derailed because gwern is trying to distinguish between the spacing effect the testing effect, and Supermemo/Anki. See gwern's literature review for clarification. In a domain where what counts as 'testing' isn't clear, perhaps basketball, then you might just try to used spaced repetition, which is what gwern is suggesting I think.
Space and testing effects are different, but work well together, and Anki/Supermemo are software that try to take advantage of these effects.
I'm interested in trying to make better Anki decks for the LessWrong community, but I want to see how well I can actually do this first. There's a lot of knowledge out there about how to format and create decks, but it's still a decent amount of work, and there are lots of people who would benefit from Anki decks, but who wouldn't make them themselves.
In order to test my deck-creation skills, I'd be willing to do a summary + deck of a chapter or two of a book, then release them to the community for feedback.
I have two questions:
These links are fairly useful/relevant.
http://www.gwern.net/Spaced%20repetition
http://www.supermemo.com/articles/20rules.htm
As a side note: I still do intend to do this, but have been fairly busy with the start of this semester. If there's no progress by March 1st, then you should consider this to be on indefinite pause.