Far be it from me to debate Almighty Science or Almighty Headlines (the real culprit here, for oversimplifying the study’s conclusions), but I think the differentiation might not be in degree of motivation, but the target of that motivation. Yes, I would be just as motivated if I were stoned, but instead of being motivated to code the blog, drive to the store to get things I need, or solve some fun logic puzzles, I would be motivated to watch some comedies, eat some pizza and take a little nap, and I would probably be much happier than I am at a keyboard.
By the way, where would jokesters be without new studies? The studies, and the often errant headlines describing them, are the very lifeblood of humor for people like Seth Meyers (yes, and me).