I believe that it all depends on whether you are 'thinking' 'working' in your mind. If you are visualizing something you are about to do/or build, pot is definately mind expanding. I can't tell you how many times i've had a stroke of genius while I was smoking. But at the same time, if you have to perform a motor function where your senses have to co-work, like driving, talking, explaining and putting together many separate ideas is difficult.