It has been studied and it's actually usually not recommended. This is the principle of interleaving. See Make It Stick, especially chapter 3. See also the recently linked document by richard_reitz.
Upvote for references, links, and avoiding weak anecdotal evidence.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.