When you say smarter, I think of "using your intelligence in a wise and intelligent manner", and I would say that in most cases, DMT does indeed improve your smartness. But mostly through alteration of previously engrained emotional habits that get in the way of cognitive clarity and general awareness.
Whether it increases your IQ or not, is a completely different matter. I think that perhaps at lower doses, mostly due to its highly energetic effects (and lack of focus-diverting visual activity), it could actually be a quite potent cognitive enhancer. If somebody can make a slow-release version of a low dose of DMT and have them do mental puzzles (Raven's Progressive Matrices), I have a feeling that it would improve their scores. Creatine does the same too - and we're talking healthy individuals here, not people with "ADHD" or any other mental disease - simply by improving molecular energy processing the brain simply performs better.
I'd say that intelligence ultimately comes down to mental energy. If you have boundless amounts of mental energy, you are more capable of picking up information (IMO) and add that measure to a childlike sense of wonder and curiosity, and you're what people would call "highly intelligent". Why? Not because you know how to solve an IQ test; but because every day, your goal is to learn more about the world, your surroundings and to parse as much information as possible. And additionally, there's a positive feedback loop on this stuff. You get entranced by these good habits; the brain is plastic, it adapts quickly; the more information you feed it, the faster it will learn to pick up even larger amounts of information.
So to answer your question shortly, I'd say that DMT definitely pushes a person in the right direction of using the intelligence they were granted in the first place, and subsequently increase said intelligence (and a circle closes...)
Sometimes this happens because the hyperslap is so severe that the person realises what a scumbag he has been lately and finally changes his habits around (not only acting more intelligently towards himself, but also towards others; a sense of communal responsibility, perhaps - "If you've been everyone/everything not caring gets harder") other times because all the person needed was a refreshing insight into the nature of reality to spark that boundless amount of curiosity that flows amidst the center of every person's being or even the depressive who is so stuck in negative thought-patterns that seeing even a glimpse of another perspective propels that person out of the depressive thought-loop and wakes up finding colours brighter and a love from within that was not noticeable before.
On top of all this, there's the basic psychopharmacological basis for saying that this molecule would make you "smarter". All its action on 5-HT receptors and in particular with its affinity for sigma-1 receptors and trace amine-associated receptors (TAAR), is -- to me -- highly suggestive of a compound that causes the brain to dump out loads of neurotrophic factors and neurogenesis promoting molecules.
