For me the effects aren't too related. Amphetamines provide focus and energy. LSD makes my mind extremely porous, so that information just goes in and I don't have to expend any effort to learn complicated things. So I don't actually do active work on LSD, I just read, and experience reading comprehension on a level I don't know how to achieve any other way. It's the closest thing I can get to "download this book into my mind" a la The Matrix.