I've seen this debate rise again and again in psychedelic circles, usually with two camps, each bearing what I consider to be an extreme and unworkable opinion. One camp says, "Yes, absolutely, psychedelics make you smarter. Of course they do. Take 'em and get smarter." The other camp, equally ridiculously, says, "No, under no circumstances can you ever become smarter from psychedelics no matter what, ever."
Neither of these positions seems very profitable to me. What my experience, and the experience of those I've known, has suggested, is that psychedelics are catalysts for expanding the possible. They make tools and perspectives available that might not have been available without them. What I DO think is that, if you are driven to seek intelligence and understanding, if you crave learning and comprehension, then when combined with a number of other practices (a healthy diet, a daily life filled with new ideas, a focusing practice such as yoga, etc), psychedelics make it possible to access tools to increase your intelligence.
In short, they make it possible for YOU to make YOU smarter.