FWIW, I tend to find that it doesn't have to be a full brain idle. Some active component seems to be helpful, but I think it needs to be easy to pause and that

FWIW, I tend to find that it doesn't have to be a full brain idle. Some active component seems to be helpful, but I think it needs to be easy to pause and that there's a sweet spot on the amount of engagement. Reading actual books or other longform documents is usually pretty fertile/generative. Watching youtube or a movie or listening to a podcast doesn't do the trick. Writing and editing are both also pretty good. Walks are good, but biking/running/swimming don't seem to be. Programming can be good in the sense that it regularly reveals missing tools/libraries, but I don't find the work itself all that generative.