Are there any readily available herbs or compounds which can improve cognitive function (aka make one smarter)?
user
Cognition enhancing drugs also known as Nootropics as it is known might not be helpful. The evidence of the performance and safety of such drugs are lacking in evidence. The circuits involved in the human brain in relation to cognition is not well understood so the best known way for optimizing cognitive function is best achieved through getting enough sleep, eating a nutrient-dense diet, and managing your stress.

There are no readily available drugs that enhance cognition because very little about the brain is fully understood. If you have any further questions, I would be happy to answer it to the best of my abilities.
assistant
Are there any which help promote cognitive development instead of just temporarily improve cognition?
user
The brain is similar to a muscle, if you are actively using it, you can permanently improve your cognition but I don't believe there are external ways or drugs that would promote cognitive development. Your health might affect your cognitive development but that there are many factors that might contribute or withhold it, it's a combination of multiple healthy habits like diet, exercise, sleep, and others that might help you.
assistant
Where is the medical proof of that statement?  Muscle and brain tissue is made up completely different matter!
user