I haven't tried shrooms, but I did try once a very small amount of cannabis. I didn't experience anything unusual except that my imagination became very crisp: it's usually hard to visualize complex things, as they tend to float away and vanish, but that time whatever I was imagining, remained surprisingly stable. I was able to visualize complex patterns with very fine structure. FWIW, I have a very strong math background, I'm specially trained to focus my mind and can invoke certain unusual effects without drugs; yet that cannabis definitely did something I wasn't able to do on my own. Edit: There is a way to switch from the "3D" imagination to the "4D" one, like some people say here, and it's indeed hard to transfer knowledge from the "4D" mode to the "3D" one [because our "3d" memory isn't quite fit for the "4d" thoughts, so it's lossy transfer?]. This surprising similarity of experiences makes me think that shrooms switch your brain to that mode, without any special training.