Cannabis slows down certain abstract thinking abilities and you basically think differently for a while. This can be an amazing insightful juxtaposition to normality. I suspect it is the effect on the short term memory centers that make it more difficult to hold complex ideas in your head long enough to find results. I personally do not enjoy critical thinking when partaking. I can feel the deficiency. It does seem to open my creative side, and for me goes best at the end of a long day like a glass of wine or video game.