Where's the research on that? I would be tremendously surprised if that result held for learning a variety of interwoven topics that depend on (or are at least

Where's the research on that? I would be tremendously surprised if that result held for learning a variety of interwoven topics that depend on (or are at least related to) each other, e.g. a bunch of CS classes. I'd be similarly surprised if that result held for learning something that you also use regularly as part of your hobby or job (e.g. programming).